quote Originally posted by zzzhuh: Because my car is almost 30 years old, putting premium in it keeps it clean and doesn't necessarily harm the engine. I know when I worked at a gas station we might of had 91 octane but the additives inside of our gas was not even close to being as good as a close by shell's 91 "v-power."

I don't know what station you worked at, but there's a difference between top tier gasoline, and everything else; and it's not just the additives. Also, higher octane fuel doesn't clean carbon deposits out of a car, it will only make them worse, without sufficient cleaning agents to help get rid of the deposits. Those same cleaning agents are also in the lower grade fuels these days. Also, ethanol is a natural cleaning agent, so the 10% mix is going to keep the carbon deposits from building up, anyway. You're also going to need some pretty heavy carbon deposits to have need to jump all the way to 91 octane in a car, and somehow use that as a rational argument. And if you have that much carbon in the engine, it's probably more appropriate for a rebuild, than higher octane fuel.

quote Originally posted by dobey: "Runs hotter" is also BS. Alcohol (ethanol/methanol) powered engines actually run cooler. That's why alcohol dragsters tend to spend more time warming up in the pits, than gasoline powered cars. If you want to make broken political conspiracy arguments, please go to T/OT where those threads belong.

Are you saying that ethanol is in the gas for political reasons?

No argument. Stating experience. YMMV, but I followed the evidence. I would like to get better mileage and performance. If the OP found a verifiable way to do it, I'm for it. I just need verification. Rather than shoot it down with propaganda, perhaps your efforts could be put more to use to assist with the goal of the thread.

Alcohol dragsters are totally different. Some street cars run both ethanol & gasoline. Drive one, testing with both fuels. Sorry to pop your bubble. With the advent of ethanol in NASCAR, the air vent in the front wasn't enlarged for nothing.

[This message has been edited by tshark (edited 07-14-2014).]

I do agree with everything above.

Lead as I always understood it, was in gas primarily to lubricate the valves. Cars designed to run on leaded gas had problems with burned valves when they ran unleaded gas. Thats the reason when I had my Superbee engine rebuilt, I had them put in hardened valve seats. Thats what happened to the original engine in it. After I put lots of miles on it all the valve seats burnt, giving it a very rough idle and loss of power.

We used to blow out carbon deposits in cylinders by revving the engine slightly and trickling Coke into the carb. Later went to a mixture of alcohol and auto trans fluid. All the junk and black smoke would go out the tailpipe.

[This message has been edited by rogergarrison (edited 07-15-2014).]

quote Originally posted by tshark: Lots of flaws: 1. First of all, higher octane in and of itself doesn't cause deposits or make them worse. Unburned/partially burned fuel does, regardless of octane. Cleaning agents cause problems of their own. Pure ethanol, before the denaturing process, is a good cleaning solution. Unfortunately, the process of denaturing requires an agent be added to prevent the ethanol from absorbing harmful water. The agent in ethanol IS dirty, which is why manufacturers require separate cleaning agent/lubricat additives. 2. No matter what cleaning agents are used, deposits will occur with the wrong octane fuel. 3. We have 3 octane levels of fuel here: 87, 92, 95. We don't have 91. If I move up from the 87, but not to 95, I can only choose 92, or try to add octane myself. My bike required 91 octane. I ran 92 in it. I have no idea how to advance the timing on a bike, and never tried. 4. If the ethanol is a cleaning agent and prevents deposits, the OP should be able to run the highest octane available at the pump without deposits. Like I said, lots of flaws. Bottom line, you can't use theory to disprove facts. An engine with high carbon deposits won't get high MPG or performance. If the OP is willing to test, I'm willing to benefit from the results. Personally, I have had poor results with shell gas, and conventional wisdom suggests that higher octane than required causes deposits; however, it used to be suggested to run the higher octane to burn off existing deposits, just like burning out creosote from a chimney. Cleaning agents are used in gas, and listed separately from ethanol. Perhaps there didn't, as you suggest, used to be cleaning agents in the lower tier fuels, and it was the cleaning agents in the higher tier that helped, rather than the higher octane. Sometimes facts outweigh conventional wisdom.

Your incomprehension of a statement does not automatically induce flaws in the statement.

1) I never said higher octane automatically introduces more deposits. I very clearly said higher octane fuel in an engine not designed to run it, will result in less of the fuel being burned, and thus will increase carbon deposits.
2) I never said cleaning agents don't eliminate deposits. They do help clean them, and reduce the occurrence though. However, they do not mitigate the effects of increased deposits possible from running the wrong octane fuel in an engine. Less fuel being burned will still result in more deposits.
3) Whatever octane levels of fuel are available in your area are totally irrelevant to the burn rate of those fuels, or how much carbon depositing will occur as a result of using them.
4) I don't know where you learned to read, but you're taking a couple of words and turning them into a very different statement produced from your own mind, and not one that was posted by me; and attempting to displace it as a statement of my own. It is not. I never said such a thing.

Bottom line, you can't disprove facts with theory. So stop trying. The old suggestion of "run a tank of premium to clean the engine" is from the days when lower octane fuels did not have cleaning agents/ethanol. When only premium fuels had the cleaning additives, it was a somewhat reasonable suggestion, as you would run it for only a tank or two, and the cleaning agents would break up the existing deposits. Then you would return to using the regular fuel required by the vehicle. Facts always outweigh conventional wisdom. The only thing that conventional wisdom is without facts that support it, is bullshit.

Dobey, I am looking for facts, not attacking you. Insults have no place here. I refuse to continue this. I have nothing to prove, and no agenda to push.

I hope the OP will continue to provide details without fear of being attacked by such as dobey.

quote Originally posted by dobey: The old suggestion of "run a tank of premium to clean the engine" is from the days when lower octane fuels did not have cleaning agents/ethanol. When only premium fuels had the cleaning additives, it was a somewhat reasonable suggestion, as you would run it for only a tank or two, and the cleaning agents would break up the existing deposits. Then you would return to using the regular fuel required by the vehicle. Facts always outweigh conventional wisdom. The only thing that conventional wisdom is without facts that support it, is bullshit.

Very true. Back in the day gas vendors used to (at least claim) their premium fuels had the most detergents to try and sell people higher octane gas at a higher profit. Once the studies came out that higher octane gas resulted in more pollution and less economy from cars not designed to use higher octane levels (like, say, a Fiero) there was a series of changes resulting from advertising and legislation pushes. In California, for example, they limited the maximum octane fuel people could buy to 91 and required all fuels from a given supplier have similar detergent levels. At the same time, the "Top Tier" gasoline initiative kicked off requiring the same. Other laws were passed locally and Federally elsewhere. AFAIK, nobody sells gas with varying grades of detergents anymore.

As Dobey has said over and over, there is about zero reason to run anything other than an engine's recommended fuel - you aren't winning anything, and you're probably losing quite a bit. One thing GM has done extraordinarily well over the years is build engines that run happily and reliably on stupid-low octane gas. It's kinda crazy.

One other thing: Altitude further reduces the octane requirement of an engine. Thinner air effectively lowers the compression ratio of the engine. That's why you can buy 85 octane fuel in Colorado - you won't see that stuff in the midwest or on the coast. If you're in Denver running 94 octane fuel in a stock Fiero, you're not doing anyone any favors.

quote Originally posted by tshark: Dobey, I am looking for facts, not attacking you. Insults have no place here. I refuse to continue this. I have nothing to prove, and no agenda to push. I hope the OP will continue to provide details without fear of being attacked by such as dobey.

Then stop posting nonsense like this. All I'm doing is asking for facts, and instead you decide to post and claim I am attacking the OP, and the he somehow is fearful of my posts. So instead of not attacking me you go on to attack both myself and the OP in the same sentence. Well done, hypocrisy. Stop trying to play the victim when you're the one making the insults.

Now if you're done with your nonsense, maybe we can go back to the actual topic and not how many people you think corn used for ethanol might otherwise feed.

Wow! This thread seemed to have turned a little nasty purely out of nowhere. I understand Dobey's skepticism and even I don't FULLY understand why my Fiero seems to react better on higher quality gas, along with apparently getting better gas than most 5 speeds.

But I CAN tell you my personal experience and people can take away what they want from that.
I would encourage people like Dobey to test it out themselves, and display there results on this page.

Let's get back on topic though shall we?

I filled up with 91 octane %10 ethanol and am still using that tank. When I fill up again, I will take pictures of my tip odometer/gas gauge along with how many gallons I put into my tank so every one can calculate the math in case im doing simple math wrong .


*OFF TOPIC*
Didn't want to start a new thread but new things always pop into my head when im driving my 86'. I recently spilled some energy drink on my cloth seats and couldn't find a good thread on cleaning the seats. What product do you guys use?

quote Originally posted by dobey: Thanks. To be more accurate, the compression ratio stays the same. What is lower is the effective displacement. You're compressing less oxygen, because the air is less dense, so it's similar to having a smaller engine. You will lose some power, but you will get a little better MPG. It's the opposite of having a turbo (and compensating for high altitude air pressure is exactly why turbochargers were invented). With a turbo, you're effectively increasing the displacement, by forcing more air into the cylinder. You get the power benefits of a larger engine, but can retain the fuel economy of the smaller engine.

HAHAHAHAHAHAHAHAHAHA... I'm not going to even bother to get into this.. but only ask DOBEY (mr 4:20) do you know the difference between static compression and dynamic??? the post above says you have zero clue.. but I need another laugh.. so have at it..

quote Originally posted by E.Furgal: DAWN DISH soap.. and hot water then suck it all out of seat with wet/dry vac.. repeat if needed..

My man you rock! I looked up some info on other sites and that is what people recommended, thanks for the input.

quote Originally posted by E.Furgal: HAHAHAHAHAHAHAHAHAHA... I'm not going to even bother to get into this.. but only ask DOBEY (mr 4:20) do you know the difference between static compression and dynamic??? the post above says you have zero clue.. but I need another laugh.. so have at it..

I'm not going to even get into this, but here, I'm going to get into this.

Great job not getting into whatever it is you're not trying to get into.

Obviously you don't understand the difference between them. The dynamic compression ratio does not change because one is in the mountains instead of at the beach. What changes, is cylinder pressure. DCR and cylinder pressure are not the same thing. DCR is always lower than SCR, and stays the same until the cam timing is changed. And advancing the cam will result in a higher DCR than stock, as the intake valve will close earlier, while the piston is lower in the cylinder.

So put down that joint, and go read a book or something, so maybe you will get a clue.

quote Originally posted by dobey: I have not seen ethanol-free fuel anywhere in a very long time. My Fiero is also not running at the moment, so I couldn't test in it if I wanted to; and when I eventually do finish the long-in-progress engine swap on it, it will have to run on premium anyway. I have run tanks of 89 or 93 in it in the past though, for the "higher grade fuel will help clean the engine" reason, and I can tell you that I never got any better MPG by running the higher grade fuel, or any better performance out of the car. The engine performed basically the same, and I got roughly the same MPG (less than 1 MPG difference, so statistically invalid). As for the seats, given their age, you might want to just go all out and do a full deep clean on them with a carpet shampoo vac. You'd be surprised what kind of stuff seeps into the seats over 30 years.

http://pure-gas.org/ scroll to the bottom and click on your state, from there you can find a gas station in your town that sells ethanol free gas. Believe me, you'll notice a difference (besides a smaller wallet.) I had no idea your doing an engine swap, what are you putting in?

quote Originally posted by zzzhuh: http://pure-gas.org/ scroll to the bottom and click on your state, from there you can find a gas station in your town that sells ethanol free gas. Believe me, you'll notice a difference (besides a smaller wallet.) I had no idea your doing an engine swap, what are you putting in?

Yeah, that site doesn't really have anything close to me at all. As for the engine swap, it's an LS4 mated to the F40 6 speed.

quote Originally posted by dobey: Yeah, that site doesn't really have anything close to me at all. As for the engine swap, it's an LS4 mated to the F40 6 speed.

Very nice! I want to do an ls4 but im leaning towards an L67 mainly because of cost/power. Why do people choose F40's and F23's for the Fiero?

Since all gas has cleaning agents in it, ethanol shouldn't be needed. Besides which, it does have a higher octane rating, around 100-105.

Unfortunately, none of those stations are close to me. For anyone who is close, what is the price difference between fuel with and without ethanol for the different grades, in the same locale?

[This message has been edited by tshark (edited 07-16-2014).]

I think you'll find the entire reason for ethanol in automotive fuel is political. Back in the '70s when the first real emissions standards were put in place MTBE was the chemical of choice as an octane booster to offset the loss of lead in gasoline. Although other alternatives were on the table, "we" went with MTBE because - as was pointed out earlier in the thread - MTBE could be added right to existing pipelines. By the mid '80s or so, most cars on the road didn't need octane boosters anymore and MTBE could have been removed from fuel systems. IIRC, in many situations it was. However, around that time there was an increased interest in "winter emissions" from gas powered vehicles, and in '90 Congress passed the Clean Air Act requiring that in certain areas - largely cities - winter fuel be oxygenated to help reduce emissions (at the expense of economy - whatever). MTBE fulfilled this requirement, so MTBE stuck around. In the mid '90s, "winter fuel" was expanded in the worst smog areas to be year round. By that time, the evidence showing that MTBE could seep out of tanks and pipes and into groundwater resulted in a swift removal from MTBE from gasoline - but the requirement for oxygenates was not eliminated. Ethanol performed the same function, so that's *primarily* how ethanol got into gasoline. It has nothing to do with "cleaning" or detergents.

There are other satisfactory oxygenates than MTBE and ethanol. MTBE was used on the coasts because it was easy. Ethanol was used in the Midwest because it was cheap. Since MTBE has been eliminated, everywhere gets ethanol. However, the only reason we get ethanol is because subsidies for the stuff make it cheap. It's not the best, it's not the most economical (from a raw cost-to-produce standpoint), and aside from oxygenating gasoline does absolutely nothing for anything. In many ways it's bad news - eating old fuel lines, attracting water (in its natural form - ethanol in gasoline is treated), phase separation (resulting in higher octane fuel at the bottom of the tank than the top), and others. In common fuel used in common ways - that is you fill up your tank with E10 and drive it until its empty - E10 fuel has an equal or less octane value than pure gasoline of the same quantity. The only scenario where ethanol fuel produces a greater-than-gasoline octane value is in greater than E10 ratios. Ethanol has a lower energy potential than pure gasoline, so whether it's E10 or E85 you're getting fewer miles from the same volume of fuel. in E10, that's all loss - less economy and no more octane. In E85 configurations, at least you can benefit from increased knock resistance while losing 15-25% of your economy per volume. However, AFAIK, the only way to take advantage of that knock resistance is with compression (either static or dynamic). I don't think you can take actual advantage of E85 with just timing, so E85 is pretty much lose-lose when it comes to naturally aspirated street cars. E10 is lose-lose everywhere, save from an emissions standpoint.

In any case, the only place you'll find non-oxygenated fuel is at specialty gas stations (boats, race cars, etc.) or away from small cities in the warm months. In practical terms, I'm not sure running pure gas really wins anything on most street cars. The slight loss resulting from E10 is probably not going to be noticed on anything other than truly high-strung vehicles or hi-po vehicles (especially boosted cars) from the decades past - where they lacked fancy electronics to make up the difference. That's my $0.02, anyway.

Wow! Thesameguy, that was a very cohesive, well-written post. You touched on the why of things, rather than just the facts.

I”m again curious about my increased MPG through the mountains to Virginia with non-ethanol fuel, though.

+1 for you.

Oh, you will probably see an increase in fuel economy with pure gas. The improvement will vary depending on the nature of the car's engine management, but anywhere from 6-15% is within reason. For most folks, though, that improvement won't offset the cost of getting the gas - whether it be the extra per-gallon cost or the PITA factor in getting it. If you're paying a $0.50 or $1.00/gallon premium for the stuff (a 13-26% premium over the national average for 87 octane) to get a 6-15% boost in economy, you haven't won anything.

A simple question that should produce some interesting answers.....
Do higher octane fuels produce more power?

I pay about $.50 more for ethanol free fuel.

I have to use it in the boat and the various small engines that don't get used regularly but I use it in the cars as more of a statement. Meaning that if I can help change the stats on the usage of this boondoggle fuel then maybe at some point the powers that be will realize that many of us don't want to burn our food in our cars.

I know it's less than a drop in the bucket but we gotta start somewhere. And yes, I know that not everyone can make this choice due to financial considerations.

Well, $.50 more per gallon in a fun car isn't bad. It's less than a 12-gal tank. Of course, more fun, but better for the car also. I wonder what the cost difference is there.

quote Originally posted by thesameguy: I think you'll find the entire reason for ethanol in automotive fuel is political. Back in the '70s when the first real emissions standards were put in place MTBE was the chemical of choice as an octane booster to offset the loss of lead in gasoline. Although other alternatives were on the table, "we" went with MTBE because - as was pointed out earlier in the thread - MTBE could be added right to existing pipelines. By the mid '80s or so, most cars on the road didn't need octane boosters anymore and MTBE could have been removed from fuel systems. IIRC, in many situations it was. However, around that time there was an increased interest in "winter emissions" from gas powered vehicles, and in '90 Congress passed the Clean Air Act requiring that in certain areas - largely cities - winter fuel be oxygenated to help reduce emissions (at the expense of economy - whatever). MTBE fulfilled this requirement, so MTBE stuck around. In the mid '90s, "winter fuel" was expanded in the worst smog areas to be year round. By that time, the evidence showing that MTBE could seep out of tanks and pipes and into groundwater resulted in a swift removal from MTBE from gasoline - but the requirement for oxygenates was not eliminated. Ethanol performed the same function, so that's *primarily* how ethanol got into gasoline. It has nothing to do with "cleaning" or detergents. There are other satisfactory oxygenates than MTBE and ethanol. MTBE was used on the coasts because it was easy. Ethanol was used in the Midwest because it was cheap. Since MTBE has been eliminated, everywhere gets ethanol. However, the only reason we get ethanol is because subsidies for the stuff make it cheap. It's not the best, it's not the most economical (from a raw cost-to-produce standpoint), and aside from oxygenating gasoline does absolutely nothing for anything. In many ways it's bad news - eating old fuel lines, attracting water (in its natural form - ethanol in gasoline is treated), phase separation (resulting in higher octane fuel at the bottom of the tank than the top), and others. In common fuel used in common ways - that is you fill up your tank with E10 and drive it until its empty - E10 fuel has an equal or less octane value than pure gasoline of the same quantity. The only scenario where ethanol fuel produces a greater-than-gasoline octane value is in greater than E10 ratios. Ethanol has a lower energy potential than pure gasoline, so whether it's E10 or E85 you're getting fewer miles from the same volume of fuel. in E10, that's all loss - less economy and no more octane. In E85 configurations, at least you can benefit from increased knock resistance while losing 15-25% of your economy per volume. However, AFAIK, the only way to take advantage of that knock resistance is with compression (either static or dynamic). I don't think you can take actual advantage of E85 with just timing, so E85 is pretty much lose-lose when it comes to naturally aspirated street cars. E10 is lose-lose everywhere, save from an emissions standpoint. In any case, the only place you'll find non-oxygenated fuel is at specialty gas stations (boats, race cars, etc.) or away from small cities in the warm months. In practical terms, I'm not sure running pure gas really wins anything on most street cars. The slight loss resulting from E10 is probably not going to be noticed on anything other than truly high-strung vehicles or hi-po vehicles (especially boosted cars) from the decades past - where they lacked fancy electronics to make up the difference. That's my $0.02, anyway.

yup all political...
as ethnol doesn't clean up emmissions.. it does as P.P.M. but when you use the correct math to factor in the mpg loss from the ethanol.. it's dirtier.. but it did two things.. 1) help corn farmers.. and/or farmers in general.. so that lobby was happy.. even tho it also made cattle/fowl farmers cost go up bigtime and made food cost go up.. 2) it made the oil companies happy.. and the tax man happy.. first the oil companies.. they knew that fuel use was going down and with c.a.f.e. regs it was only going to get worse as vehicles got better mpg.. the ethanol.. forces the person at the pump to burn more gallons of fuel than if it was 100% gasoline.. slowing the use decline a little.. that's my only complaint of oil companies.. unlike others that cry about their profits.. as they only make a penny or two on every gallon.. it's the volume of sales that make that huge profit #... then the tax man,, as the fed and states have fuel tax.. if you burn more they collect more.. this helped them put off raising the fuel taxes to make up for the decline of fuel use.. or not raise them as much.. and kept the taxpayers from see'n red.. decline of use will be the reason fuel taxes will go up and a milage tax will more than likely come to pass.. to make the hybrids and electrics pay their share of the road cost... but that another topic..

the biggest issue is that ethanol fuel isn't kind to cars fuel systems..boats and small engine equipment is another topic.. you can't let it sit as it goes bad fast.. and eats parts.. as ethanol doesn't stay mixed with the base fuel.. it seperates.. and it doesn't take long when car isn't moved for this to happen.. it loves to suck up water.. not good for steel tanks/lines/etc.. does alum no favors.. A car that requires 91+ that sat for a day or two when started might get (suck from the tank)75% ethanol.. and an octane much lower than the car NEEDS.. when it get the gasoline with out the correct % of ethanol to bring the octane to it's r+m rating.. this can and has shattered pistons.. .
I hate the stuff.. but every pump here has it.. it waste more energy to make it than you get from it.. it's not"GREEN not by a long shot...
it was a stop gap that needs to go bye bye.. it's usefulness if long over..

[This message has been edited by E.Furgal (edited 07-16-2014).]

quote Originally posted by olejoedad: A simple question that should produce some interesting answers..... Do higher octane fuels produce more power?

NO. It will only ALLOW you to modify engines to produce more. (ie/ you can make it higher compression, run more aggressive ign advance, etc) If you check an engine on a dyno and find its got 200 rw horsepower on regular 87, putting in 93 octane is not going to show the same engine now miraculously has 220 hp any more than putting a Moroso sticker on the fender.

[This message has been edited by rogergarrison (edited 07-16-2014).]

quote Originally posted by rogergarrison: NO. It will only ALLOW you to modify engines to produce more. (ie/ you can make it higher compression, run more aggressive ign advance, etc) If you check an engine on a dyno and find its got 200 rw horsepower on regular 87, putting in 93 octane is not going to show the same engine now miraculously has 220 hp any more than putting a Moroso sticker on the fender.

double edged question.. most of todays cars.. ecu can make more power with higher that "required" octane.. as the ecu will advance the timing of each cylinder firing independently until the ecu gets feed back from the knock sensor.. cars with synquental ing and efi made the last 5 years(give or take) can make use of the extra octane.. with in the limits of the design of the engine and ecu software.. and is why handheld power programers can make more power without touching the hood latch.. as the oem need the car to last as long as possible so the tunes are very mild.. even when scanned/data'd with better than required octane fuel.. you can log/scan real time with the good scanners.. and you'll see the timing curve and cyl firing change from when logged with the required octane fuel. and then again with the better than required octane fuel. if they got nothing from it.. the data/scan would not show a change in the timing of injector firing and spark firing.. but for cars like the fiero.. getting fuel with more octane than needed.. is just spending money for zero gain..

I understand all that pretty much...but what Im saying is JUST the use of higher octane alone is not making more power. What you describe is what Im saying...it ALLOWS different things to be modified from original to make more power...whether thats by manual adjustments, ECM or an aftermarket tuner. Use a 70s car as an example, pre electronics...just putting in 93 instead of 87 would not produce any more power at all. It would just cost more to fill the tank and in fact you may lose some performance.

[This message has been edited by rogergarrison (edited 07-16-2014).]

quote Originally posted by zzzhuh: Very nice! I want to do an ls4 but im leaning towards an L67 mainly because of cost/power. Why do people choose F40's and F23's for the Fiero?

The F40 and F23 are the strongest rated manual transaxles available from GM with the metric bell housing patterns. The F40 also gives you an extra gear, which is nice. If one wanted to do an Ecotec swap though, some of the other manual transmissions with the Ecotec bell pattern would be better than the F40/F23 though; not necessarily stronger, but better matched to the Ecotec engines, and with better gearing for getting max cruising MPG.

On the other hand, it's nice to see this thread has turned totally political in the last 12 hours. :-/

quote Originally posted by rogergarrison:it ALLOWS different things to be modified from original to make more power...whether thats by manual adjustments,

Indeed, and I wonder how important that is going to actually be going forward. With direct injection, the need for knock resistance in the fuel is dramatically reduced, to the point it might be eliminated for common purposes. i think the current crop of direct injected/forced induction engines run happily on regular fuel - even Hyundai is running 16+psi on 87 octane on the GDI turbo. By all accounts, the "premium" requirement on the LNF was somewhere between CYA and marketing. If the fuel is always perfectly timed - versus squirted in one place and then forced to travel to reach its final destination - what is that higher octane actually protecting against? Hmmm....

If I remember right most turbo engines are lower compression. Which means made for low octane. There seems to be a turbo revival these days in order to meet mpg requirements.

My Ferrari kit with a moderately modified turbo 3.1 had I believe 8 or 8.5- 1 compression. I drove it 100K on 87 octane with no problems at all, along with a 160* tstat. With a 185*/195* it would ping like hell. It was as fast as a hungry cheetah too.

Yeah, but that's all old technology. With port injection fuel timing and flow is highly inaccurate and there is a significant potential for spontaneous ignition (knock). HIgher octane make fuels resistant to knock, and lower static compression reduces the likelihood. Since forced induction increases the effective compression ratio of an engine, static/mechanical compression is generally reduced accordingly to stave off knock. With direct injection, the fuel timing and flow is highly precise, and there is a significantly reduced (virtually eliminated) potential for knock. Whereas port injected naturally aspirated motors are limited to 9:1 or 10:1 compression ratios with low octane fuel, direct injected naturally aspirated motors can easily run compression ratios of 11:1 or 12:1 on low octane fuel. In the past, a 12:1 compression ratio on a street motor was borderline nuts and certainly called for high octane fuel - with direct injection it's not an issue. Similarly, in the past you'd find most port injected forced induction motors running compression ratios of 7:1 or 8:1 with more recent turbo motors (eg Saab) with 9:1. Modern direct injected forced induction motors will run 10:1 or 11:1 - CRs previously considered pretty high for naturally aspirated motors. The aforementioned Hyundai turbo runs a 9.5:1 compression ratio AND 18psi on 87 octane gas, making 274hp from 2.0l. That is NUTS.

And that's my point - if you can get a factory-reliable 150hp/liter from direct injection + forced induction on 87 octane gas, why do we even need higher octane fuel anymore? My bet is that 2014 is like 1976 - when leaded fuel disappeared and all the people with old cars were like, "What about us?" Those of us with old turbo and hi-po NA motors that will kersplode themselves with low-octane fuel are about to be really sad. Time to stock up on octane boosters, or convert to E85.

So:

2.5: Lower static compression, yes, but boost pressure increases the effective compression ratio bumping the octane requirement significantly. My XR4Ti has an effective compression ratio of about 22:1 (8.5:1 static + 22psi of boost).

rogergarrison: Since turbos provide a dynamic increase in effective compression (0psi to max psi), it's not fair to say "100k on 87 octane with no problems." If you're only running a few psi of boost, or don't have a lead foot, or have made other compromises (like reduced ignition timing) you will get very different results from someone running 20psi with it floored all the time and highly advanced ignition timing. Yeah, some engines manage forced induction better than others, but at the end of the day there are basic rules of engine design you just can't get around. Not to suggest you don't know that, but others might not.

I figured I would do a quick update here. First off, im surprised this post has gotten over 4 pages of stuff. Whether we agree or disagree it's nice to see everyone giving there $.02.

On the other hand I've been rather surprised with this tank of 91 octane %10 ethanol because of my gas mileage. I have been trying to keep city driving to a minimum but here are recent pictures so far.





And yes Dobey! Gas gauge, VSS, trip odometer, regular odemeter, and my camera are all working properly.