So, what kind of gas mileage do you get?
I'm starting to reconsider my future V8 plans due to escalating gas prices, and was considering a 3800SC. I've heard they can get over 30mpg with a 5-speed. I've also started thinking about picking up a Duke/5-speed for a commuter (or other econobox), especially if I go through with the V8.

So, what kind of engine / transmission are you running, and what kind of mileage do you get?

How about those stock Fieros? How much can you get out of your Iron Duke?
I've gotten upwards of 33mpg on my Formula (5-speed), but it's usually in the low 20's in town and mid-to-high 20's on the highway. The 33mpg was highway only, mainly level ground, windows up and the AC off, so that's about as good as it can get.

Most any engine can do okay on the highway... My 4.9 will deliver about 26 mpg on the highway. But if you plan on using a V8 as a commuter it's going to burn some gas. Mine will drop to about 17 to 19 around town, mainly because I can't help really leaning on it when I'm accelerating.

I'm using N* engine/trannies. Excellent gas mileage using a larger diameter rear wheel to match stock N* rims. 26.2-26.6 diameter will produce 30+ mpg hwy. I've traveled 300 miles on one tankful (11.6 gallon) at 70-74 mph. Using the N* gauge pod will desplay your adverage mileage.

Gas in some areas of San Francisco premium is $3.29 Yeah I know. I'm

[This message has been edited by madcurl (edited 08-12-2005).]

My 88 GT with the highly modded 3800SC and GETRAG only got 26+ with spirt driving.

My 88 GT with the Series III automatic setup was getting 28+ and the new owner reports 30+ on his highway commutes.

PCM tuning is critical. These are all on OBDII systems as well.

Loyde

5 speed Iron duke here.
On the way to Osage I got 34 mpg
On the way back I got 38 ( new fuel filter )
It varies depending on how late to work I am on a daily basis though.
Brad

If you want to look at other commuter's, I'd highly recomenend a saturn S-series.

SC1's with a 5spd get (I've personally seen my friend do this) 48 MPG highway, cruising 85--90 the whole time.

I got 42 highway with a DOHC (SL2) 5spd cruising 70-75.

I also got 30-35 around town with a heavy foot in that same twin cam SL2. I would recomend the SOHC for daily driving though, there power bands are opposite of each other. my friend's SOHC will pull hard off the line (it'll even put you back in the seat a little bit) but runs out of breath at 4K. My twin cam didn't start making power until 4K, but it pulled great to 6500 RPM.

Sure it's not a fiero, but the 97-99 SC1's look great, and will yeild you way better gas mileage for there power than just about any fiero.

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AIM= Fish100770
96 Saturn SL2 Turbo (evil SL2)

My cardomain site: cardomain.com/memberpage/702872

My Quad 4 5-speed got 38MPG (canadian) on the highway, averaging 130KM/h+ (80MPH), and dropping it to 4th to pass at that speed.

I am going to change my o2 sensor because I am using the original one that came with the engine, and it looks quite old. My engine has 330,000KM on it dont know it is was rebuilt or not.

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[IMG]
84 Fiero Sport Coupe #1192 :: 86 Fiero Base Coupe Quad 4 :: 84 Chevette CS 4 Door

Strictly highway, stock 4.9 with 4T60E DRIVING BETWEEN 65 AND 70 will make 32-33 mpg in the Finale all day long.
Driving closer to 80 the mileage drops to about 28. Driving over 900 miles to Osage Beach and back home I averaged 27 mpg. That included running around town, a couple of guys driving the car on "test drives" and, most important, the last 100 miles with a failing ignition module that eventually took out the coil. (My mileage for THAT 100 miles was something under 20).

The key in the 4.9 if you want good mileage is to drive the speed limit or less. The engine loafs at about 1800 rpm and just idles along sipping gas. If you feel the need for speed, you can expect to pay a little more (but still much MUCH less than the 3.4L crate motor with the TH125C)

John Stricker

PS, the only engine modification is an MSD ignition which I honestly don't think helps mileage that much, but does seem to improve throttle response and idle.

Stock 4 speed 2.8 gets between 19 - 20 in town.

quote Originally posted by jstricker: The key in the 4.9 if you want good mileage is to drive the speed limit or less. The engine loafs at about 1800 rpm and just idles along sipping gas.

This explains why I've never seen over 26 mpg; I can't keep it under 80 mph on the freeway.

My stock 88gt 5spd got 30-32 going 80-85 on the highway, but got 26-28 around town. (Very heavy-footed!)
My 86gt 4spd got 24-28 no matter how I drove it whether it was in town or on the highway when it was stock. As soon as it's running I'll post how the 4.9 turbo does.

My 84 4 banger gets 10MPG if i'm lucky in town. lol. On the Highway I get 30 MPG. Pretty sure I have an blown head gastic or somthing. lol.

quote Originally posted by cooguyfish: I got 42 highway with a DOHC (SL2) 5spd cruising 70-75. I also got 30-35 around town with a heavy foot in that same twin cam SL2.

Can you recommend any years over others?

My stock, 41k miles 1985 Duke with automatic transmission gets, on average over the couple thousand km I've put on it since I bought it, 24 miles per US gallon. Last fill was 26 mpg; didn't have any Solo competitions on that fill. Throw a couple days of Solo into the mix and the milage drops, most likely due to excessive idling to make sure the car is warm and when sitting in the grid.

I do virtually 100% around town driving with the car, plus some Solo.

I'm jealous of you swapped engine guys if you're getting better milage than me

EDIT: Just so you know, I drive like a granny most of the time...

Andrew

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Proud owner of an 85 coupe with 40k miles

[This message has been edited by 85SE (edited 08-12-2005).]

We have had customers say that they get more MPG with our intake manifolds than they did with the stock units. Probably because of the fact that it doesn't go rich above 4,500 etc. Maybe this thread will get a response from a few Hi Flo users on the topic. As for my 2.8, what with the intake, other mods, and a turbo, I can't seem to resest keeping my foot out of it for enough miles to see what mpg NORMAL driving would produce. With gas prices climbing I may make it between tank fills to see what it gets when not in boost. Naw.......... that's not going to happen.

My 'low-tech' TBI 4.5 with a 4t60 gets 20~25 in town. It would be better if it were not for the 2000+ rpm converter stall speed. On the road trip to Ed's swap meet, it averaged 29 MPH for the trip with mixed city/highway driving. Not great mileage, but considering my van gets 16~18 with the air on, the Fiero is getting the daily driver duties.
My old 88 GT/3.4 with an Isuzu would get 20 MPH in town and a little better than 30 on the highway, about the same as my original 85 Duke.

quote Originally posted by ryan.hess: Can you recommend any years over others?

It might be better to ask on the saturn forum ( turbosaturns.net ) but what I can tell you is that 96 is when they switched to OBDII, and I'm not exactly sure when they changed, but some of the SOHC's are throttle body injection, only 84 HP, and worse MPG. I know my 96 SL1 does NOT have a TBI, so at least 96's up should get the better gas mileage. Other than that, really check out the saturn forum, there are some sticky's on what changes over the years, but know this; the SOHC's have a tendency to crack heads, so be careful with it or at least be aware (that's what's wrong with the 96 SL1 I just picked up with 156K miles, but then again I paid $475). O, and a new head from saturn is $200.

-Fish

https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20030531-2-018929.html

i'm getting consistant 30 mpg. that's mostly hwy miles at 70 mph average. i do go through about 5 stoplights in town. oh 84 duke with 4 speed. k and n air filter is the only "mod" i have. i really don't take it easy rowing through the gears either.

My 88 2.8L Getrag consistantly gets 35+ mpg at 70 mph. That's on level roads, driving sensible.

Last May on the way to Carlisle I delivered a customers 3800SC swap I did 5 hours away. The owners location was right along or trip route, so I drove the 3800SC Fiero, and my my wife ( Blackie2m6 ) drove my car. We travelled through some hilly terrain, where the L67 powered Fiero didn't have to work nearly as hard as my stock engined one.

Blackie2m6 stopped for gas at 1/4 tank, and the L67 Fiero still had half a tank left. Both cars are pretty much the same, both 88 GT's with a getrag, other than the L67, and mine has T-Tops.

I was surprised at the mileage the L67 Fiero got. I didn't calculate mileage- both cars started at the same point with full tanks, and drove the same distance and speed, one burned 1/4 tank more, and that car burned the normal amount of fuel for that part of the trip.

I also delivered a 87 GT with a mild built 5.7L TPI and an Isuzu 5 spd to a customer near Boston Ma a few years ago. On that trip the car got extremely good gas mileage. I didn't calculate the mileage, but I'm certain it was getting well within the 30's.

What kind a gas mileage you get depends on how you drive the car. If you drive sensible, you can get good mileage with a properly tuned big engine car.

[This message has been edited by jelly2m8 (edited 08-13-2005).]

Jonathan,

Believe me, I know what a temptation it is. When I work corners and go down to Tulsa or up to Omaha, I often take the Finale if I'm going by myself because it CAN get the best gas mileage of anything I own. I just set the cruise on 70 on interstate and turn up the tunes and enjoy the double takes I get when people pass me or I pass them. Give it a try sometime. The best part is that at cruise, the exhaust just kind of burbles/rumbles behind me and there's now doubt the car doesn't have a V6 in it........

John Stricker

quote Originally posted by jscott1: This explains why I've never seen over 26 mpg; I can't keep it under 80 mph on the freeway.

My 2.8 bored and stroked to a 3.2 with the Crane 2030 cam and all else stock with 5spd Getrag gets 24 in stop and go rush hour traffic and 29-31 on the highway at 75mph.

JazzMan

Our 85se with 4.9/4t60e gets around 24mpg city and 27mpg highway
Our 87gt 2.8/5spd gets 29mpg highway and maybe 25city
The 86gt that we sold with a fresh 3.4 pushrod/5spd got 31 highway
The 88 duke got around 27mpg with it's 5spd.

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Proud Member of the North Florida Fiero club

4T60E Parks harness/ Rockcrawl chip-- more to come--

13/14 in town, 19/20 on highway sub-80mph. I did get 9mpg on one tank of gas, though hehe.

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Christian Thomas
87 Pontiac Fiero GT Burgandy/Silver 5.7L ZZ4 5spd
301rwhp/345rwtq

Next Mod: Not sure yet

On my 88 coupe with the Duke and auto, I get about 26-28 mpg. That's with a mix of both highway and city driving (yay for living in the country!), and I definetely don't go lightly on the throttle.