Is it to try and slow oil consumption, oil leakage, noise, mpg? Just curious. Also how many miles on your engine. I was hoping to get into discussion on why the "recommended" weight is 5w30, and what happens when you stray from that.
I run at least 10/40 during the winter and 20/50 in the summer because the thinner, the more I leak out. Car doesn't burn any, it only has 100800 miles on it but it leaks from the rear seal. I had the oilo changed for free one time and they put in 5/30 and it poured out
If you have leaks, it's best to fix them and use the recommended oil viscosity. The oil pump will have a harder time getting thicker oil to everywhere it's needed, and engine wear may increase.
I've bought new cars since 84 and all used 5 w 30 when new. Usually around 80-100K, I switch to 10 w 30. We generally kept a car for about 4 years and put over 35K per year on them.
Our 93 Grand Am 3.3 started the exception. We gave it to a needy friend when it had 311K on it. He replaced the timing set and drove it for another 3 years. All on 10 w 30. My 97 Dakota 5.2 now has 220K, uses 10 w 30 and still holds 50 PSI at road speeds and the 2000 Grand Prix at 180K is still on 10 w 30. My 87 GT got changed from 10 w 30 to 20 w 40 at about 90K and the engine was replaced at 135K because the oil pressure was seriously low.
I've never used heavier oil to address leak problems, but only to boost oil pressure that might be dropping or because of mileage on an engine and obviously, I get long life from my cars. Oh yes, I forgot the 85GT I gave Robs Fieros. Untouched original engine running on 20 w 40, but it was only holding about 15 PSI at hot idle with just 297 K miles.
I don't think there can be a mileage benchmark for going to a thicker viscosity. It depends upon your driving habits. Obviously, I ran the kwap out of my 87 and 85 GT's, but the 88 Duke is still pumping 60 PSI on 10 w 30, at road speeds while pushing 170K. It was always driven by adults over 40 years old, and used solely for commuting.
And I only change oil and filter every 5000 miles.
I'm currently using 5w20 in the Fiero... thinking of switching to 0w20 synthetic after the engine upgrade.
The reason why: this 3.4 crate engine was put together pretty tight. The thinner oil flows through the tight spaces better, so the bearings and stuff don't run dry.
I've been using 10w30 in my Fiero GT. It's approaching 300,000 miles. There are some oil leaks, but I'm in the process of getting them all sealed back up as we speak.
I've always been under the impression that I can't really run the "5" because it frequently gets over 100 degrees where I'm at throughout the summer, as in when you get to triple digit temps you're supposed to run "10" or above. I've just stuck 10w30 in there and gone about my business.
Today's multi-grade oils work in reverse of what physics would tell us. Normally viscosity is heavier when oil is cold and lighter when it's warm. Engine oils actually work in reverse, being thinner (5w) when cold, so it will penetrate and flow through the tighter tolerances of today's engines, and becomes heavier (30w) as it heats up.
Today's multi-grade oils work in reverse of what physics would tell us. Normally viscosity is heavier when oil is cold and lighter when it's warm. Engine oils actually work in reverse, being thinner (5w) when cold, so it will penetrate and flow through the tighter tolerances of today's engines, and becomes heavier (30w) as it heats up.
thank you. i do lube servicing as my current job and youd be surprised how many people i tell that and they tell me im lying. then out comes my book. i think with and older car 5w30 would get the oil where its needed faster when cold.
im using 5w 40 rotella due to a loss in pressure when warm. (probably faulty gauge but the oil is cheaper anyways)
Today's multi-grade oils work in reverse of what physics would tell us. Normally viscosity is heavier when oil is cold and lighter when it's warm. Engine oils actually work in reverse, being thinner (5w) when cold, so it will penetrate and flow through the tighter tolerances of today's engines, and becomes heavier (30w) as it heats up.
Thank you for pointing this out.
Many people seem to be confused by the viscosity ratings. But it's actually very simple. The first number is cold viscosity, and the second is hot viscosity.
Cold viscosity is important during cold start-up. If you have a new engine with tight tolerances, then you want the cold viscosity to be low. On the other hand, if your engine has some miles on it, and is starting to loosen up, then the cold viscosity should be higher.
Hot viscosity is important during normal engine operation. If you race the car, and/or drive it in a very hot environment, then you want the hot viscosity to be high. This also holds true if the engine is modified for high performance (i.e. big turbo or blower, or high compression). Because a high-performance engine will exert more pressure on the main/rod bearings, which tends to squeeze the oil out of the bearings. The higher viscosity oil will resist that.
It was my belief that a multi grade oil was as follows.... With 10W30, the 10 indicates the oil will have the same viscosity, when cold, as single grade 10, and when hot would have the same viscosity as single grade 30 hot. So, multigrade oil does not change viscosity as much as single grade with temperature change.
Today's multi-grade oils work in reverse of what physics would tell us. Normally viscosity is heavier when oil is cold and lighter when it's warm. Engine oils actually work in reverse, being thinner (5w) when cold, so it will penetrate and flow through the tighter tolerances of today's engines, and becomes heavier (30w) as it heats up.
Pour it out of a quart cold and drain your oil warm it has a much thinner viscosity and better flow when warm. Multi viscoity oil (5w30) is thinner cold then straight oil (30weight) is, but multi viscosity oil isn't thinner cold than it is hot.
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Originally posted by winfield:
It was my belief that a multi grade oil was as follows.... With 10W30, the 10 indicates the oil will have the same viscosity, when cold, as single grade 10, and when hot would have the same viscosity as single grade 30 hot. So, multigrade oil does not change viscosity as much as single grade with temperature change.
That is why you want the lowest first number, 5wXX, 0wXX for example in the beginning. A Xw30 and XXw30 are the same viscosity at operating temp which is why fierofools 10w30 oil isn't any thicker than 5w30 once it warms up.
quote
Originally posted by outlawfiero17:
thank you. i do lube servicing as my current job and youd be surprised how many people i tell that and they tell me im lying. then out comes my book. i think with and older car 5w30 would get the oil where its needed faster when cold.
im using 5w 40 rotella due to a loss in pressure when warm. (probably faulty gauge but the oil is cheaper anyways)
What does your book say exactly? Another thing about pressure, it is measuring resistance to flow, higher pressure if achieved by thicker oil is not better in my opinion, and as TopNotch said. As a general rule 10 psi per 1000 rpm is plenty of pressure.
Thoughts?
[This message has been edited by 2.5 (edited 03-30-2012).]
This set orf articles, oil 101 explains things well, though very detailed on the site. Viscosities, the numbers on the quarts, viscosity improvers, etc....
"Most of what I hear is the opposite of the truth. It is however easy to see how people get mixed up as there is always some truth to the misconception.
The automotive designers usually call for their engines to run at 212°F oil and water temperature with an oil thickness of 10. This is the viscosity of the oil, not the weight or grade as labeled on the oil can. We are talking about oil thickness, not oil can labeling. This will be discussed later.
A “30” grade oil has a viscosity of 3 at 302°F ( 150°C ) and thickens to 10 at 212°F ( 100°C ). It further thickens to a viscosity of 100 at 104°F ( 40°C ) and is too thick to measure at the freezing point of 32°F ( 0°C ). a 0W-30 grade oil is not thinner than a 10W-30 oil. They both have the same thickness at operating temperature. The 0W-30 simply does not get as thick on cooling as the 10W-30.
Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have far to go before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. It cannot flow and therefore cannot lubricate. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil ways. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less.
Note that a straight 10 grade oil is also too thick for your engine at startup. It has a thickness of 30. Yet at operating temperatures it is too thin having a thickness of 6. It needs to be around 10. The oil companies have added viscosity index improvers or VII to oils to solve this dilemma. They take a mineral based oil and add VI improvers so that it does not thin as much when it gets hotter.
I have always used 5w30 in all of my fieros (13 as of now I believe...lol) I did use 10w30 in my 88 Iron Duke once because I had a full bottle of synthetic in the garage. didn't notice any difference, or feel any either.
I used to run a big bore Suzuki, and it had a very touchy temp gauge. Since friction equals heat, I could get a good handle on the lube abilities of various oils and weights. The lowest temperature I ever saw in hot weather was from Trop Artic 15-40. The highest, a full 20 degrees higher, was from Bel-Ray racing oil in 5-30. I do not know the science behind this, only obseved the results. I'm running a 5-30 synthetic, but all I've seen from the rodding scene and around the net, I'd be extremely comfy with a 15-40 diesel oil. I would run no more than a 5-30 in colder weather. My engines tend to last a very long time no matter what, simply because I keep it fresh and clean, which IMO, trumps all.
I really don't believe it's as critical as people make it out to be, at least between the 30 and 40 viscosities. People get hundreds of thousands of miles out of their engines with 5w30 or 20w50 or anything in between. Probably true for the newer Xw20s as well. I think 20w50 is extreme for most engines if in good condition, but the choice between 30W and 40W hot isn't that big a deal one way or the other. Countless people have great success with both. But it's natural people are very concerned about their oil so it gets near religious sometimes.
On a car with an oil pressure gauge I don't see any need to stress about it, just look at the gauge and use what puts you in a comfortable pressure range. Not all engines are the same, especially after they've aged. No the gauge isn't perfect, but it's good enough to make a reasonable choice.
Personally I use 10w30 because it's conveniently available in the high ZDP oil I use, and I get reasonable hot pressure with it. But even if my oil had a 5w30 available I'd probably keep using 10w30 anyway. Years ago I used to like 10w40 (conventional) but don't like it as much after reading about the high level of viscosity improvers required by that formula. The VI components don't contribute to lubrication, and they do contribute to sludging. 5w30 is a more conservative formula than 10w40, despite how it might look by the numbers. But again, many people use 10w40 very successfully. It's not a big deal, just not what I pick.
When I bought my car, the hot idle pressure was so low it was starting to trip the light. I panicked and put 20w50 in it. That made my pressure way too high. I drained some of that and mixed it down to a lower viscosity, ultimately I ended up settling on the same 30W hot that GM recommended. So what was wrong? I can only assume the previous owner had left the oil in for too long and it was breaking down into something much thinner than 30. I'm glad that's all it was.
One thing I try to do is drive gently while the oil is cold. As long as the pressure gauge is sitting near max then I stay easy on the throttle and keep the revs down. You can tell when the oil has warmed up enough to flow better when you see the pressure drop markedly. I notice this happens a little slower than the warmup of the coolant.
Something else to consider is that manufacturers aren't necessarily only looking at engine life when they write these specs. They also worry about fuel mileage and power, and they have little reason to be concerned how long it lasts beyond about 150K miles and the original owner who paid them for the car. He's the customer they want to make happy. Back in the 80s I'd be surprised if they looked beyond 100K. That's not to say 5W30 won't last, I'm sure it will, but the fact GM recommended it wasn't really motivated by their opinion of how it handles old age. I'm not against 5w30, I nearly use the same viscosity myself. But I take that recommendation as a baseline, not an absolute. Biggest thing is timely oil changes, don't let your engine overheat, all that basic maintenance stuff. 5w30 or 10w40 aren't going to do anything dramatic to it.
[edit - for something I thought isn't that critical, I sure wrote a long post about it. Oil.. always gets people talking I guess.]
[This message has been edited by armos (edited 03-31-2012).]
Many people seem to be confused by the viscosity ratings. But it's actually very simple. The first number is cold viscosity, and the second is hot viscosity.
Cold viscosity is important during cold start-up. If you have a new engine with tight tolerances, then you want the cold viscosity to be low. On the other hand, if your engine has some miles on it, and is starting to loosen up, then the cold viscosity should be higher.
Hot viscosity is important during normal engine operation. If you race the car, and/or drive it in a very hot environment, then you want the hot viscosity to be high. This also holds true if the engine is modified for high performance (i.e. big turbo or blower, or high compression). Because a high-performance engine will exert more pressure on the main/rod bearings, which tends to squeeze the oil out of the bearings. The higher viscosity oil will resist that.
Thanks I did not know that. That was helpful!
------------------ 84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White
[This message has been edited by White 84 SE (edited 07-29-2014).]
I'm currently using 5w20 in the Fiero... thinking of switching to 0w20 synthetic after the engine upgrade.
The reason why: this 3.4 crate engine was put together pretty tight. The thinner oil flows through the tight spaces better, so the bearings and stuff don't run dry.
...........but, the film strength of lower viscosity oils is weaker and gives less lubrication properties. Thin oil also breaks down easier with heat. I've been using a 50/50 mixture of 15W50 and 5W30 Mobil One for years in all of my vehicles. I have yet to replace one engine so far. Years back I used Valvoline Racing oil. When it came time to refresh the engine at 150K miles I felt that a rebuild was in order. When we opened her up, we found that the cylinder bores and crank journals still met new specs.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
I always use 5w30 in my cars with the exception being my BMW which uses Mobil 1 Euro spec 0w40. When I rebuild the Fiero's engine I may consider using that after break in on it.
