Musing about lighter oils, MPG, and engine life

[Laminar Lou]

I've seen many people here state they want a thicker oil for more "protection". I am going to assume "protection" = "longer engine life".

However, if switching from 5W30 to 5W20 will increase gas mileage wouldn't one also assume that the wear would be less? This assumption is based on the logic that less fuel consumption means:

-Less fuel dilution
-Less fuel used in the combustion chamber for the same speed and therefore
Less stress on the engine.
-Possible earlier shifting into higher gears for the same speed

Is my logic flawed? I am currently testing Chevron 5W20 and 5W30 against Amsoil 0W20 and 0W30 in my Tundra to see how the UOAs look. I am also keeping diligent MPG records.

I look forward to everyone's comments.

 

[MysticGold04]

I'm looking forward to seeing your results! ... as I have been pondering going to 0w30 for some time now... just wondering if it's worth the extra $$.

 

[badtlc]

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Is my logic flawed? I am currently testing Chevron 5W20 and 5W30 against Amsoil 0W20 and 0W30 in my Tundra to see how the UOAs look. I am also keeping diligent MPG records.

I look forward to everyone's comments.

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are you running consecutive OCIs of each of those oils before getting the UOA? If you aren't making at least 2 runs of an oil before sampling, I would not take the results too seriously.

 

[Laminar Lou]

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I'm looking forward to seeing your results! ... as I have been pondering going to 0w30 for some time now... just wondering if it's worth the extra $$.

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So far I have the Chevron 5W30 versus the Amsoil 0W30 if you want to compare that. I was very happy with the 0W30. On the UOA,

 

[Laminar Lou]

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are you running consecutive OCIs of each of those oils before getting the UOA? If you aren't making at least 2 runs of an oil before sampling, I would not take the results too seriously.

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My results above answer that question. You've got a good point, the method would be more accurate with the 2 runs you mentioned. I might consider that in the future for the 5W20 versus 0W20 comparison.

I am mostly interested in MPG, the wear numbers on the Tundra are so low that it is hard to really compare them anyway. I am really doing the UOAs to check to see if the wear numbers really spike. If they do I can reasonably assume that the oil is really not right for the engine. Keep in mind, the 2002 2UZFE is not spec'd for 5W20.

But in that spirit it got me thinking that does a thicker oil really provide better protection? And hence the Original Post.

 

[Ramblin Fever]

Question - I know you're doing a study/test, but WHY are you changing out superior synthetic oil with only 3k miles on it?

I realize 8 mnths came and went between OCI's, but still, I would think a high dollar synthetic oil (the Amsoil you were using) & living in California could warrant at least a year's time & 6k miles of use.

 

[Laminar Lou]

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Question - I know you're doing a study/test, but WHY are you changing out superior synthetic oil with only 3k miles on it?

I realize 8 mnths came and went between OCI's, but still, I would think a high dollar synthetic oil (the Amsoil you were using) & living in California could warrant at least a year's time & 6k miles of use.

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I was planning on the 1 year interval, but the curiosity of 5W20/0W20 got the better of me and I drained early. It was actually closer to 9 months (the mileage comments aren't exactly when I changed the oil - I have another sheet with exact mileage and dates). However, I agree this oil could have easily gone 1 year - probably longer.

I am actually toying with the idea of adding LC20 halfway through the OCI to see if it gives me a MPG boost. Then drain at 2K, run the Chevron 5W20 again without LC20 and then add the LC20 again halfway through that cycle just for repeatability. Then do the same with the 0W20. That will take me 2 years to complete at the rate I put miles on the truck. The wife puts many more miles on the minivan and I could do more in less time with that vehicle. However, the minivan MPG is all over the place because the driving is so inconsistent. The truck is to and from work only and is very consistent so I am using it for the test bed. Even still, I plan to test the 0W20 in the minivan to see if it makes some impact just for grins. I do know that I once added VSOT in the Odyssey and the MPG took a nose dive, so there is some kind of trend - it's just not as easy to see.

Also, I am taking intake air temperature readings on the truck with my carchip. I am hoping to start correlating air temp to MPG and then use some type of formula to make adjustments. If I really wanted to make this as consistant as possible I wouldn't run the a/c, but I am not really willing to give that up in 100F heat - so my test is going to have error. All I can do is give it my best shot and try to be fair to all oils (that is also why it would be good to run Chevron 5W20 twice and the Amsoil 0W20 twice so I can get a winter and summer reading).

 

[Junior]

As you have realized, it is very difficult to determine differences in fuel ecomony on the open road. The following things could also have an affect on MPG:

Air filter restriction
O2 sensor condition
Spark Plug condition
Brakes and wheel bearings
Tire inflation
Driving speed
Wind
Engergy content of the fuel
Changes in Frictional power of engine due to wear

I commend your effort and it will be interesting to see what your results are. Personally I haven't seen much of a difference in MPG between 20 and 30 Wt. But if in the end, you find something that fits your driving style and vehicle use then it will be worth it to you.

I have always wondered if Xw20 pumps easier but Xw30 seals the pistons and rings better and they tend to ofset each other. This would probably be more apparent in a more worn engine rather than a new one. I dunno

 

[Laminar Lou]

Junior,

All very good points, and I understand that. All I can do is hope to show some trend over time. It's not perfect science, but it is something.

I think I pretty much thread jacked myself, as the original purpose of this thread was to see what people thought about engine wear and lighter oils. Any other comments on the original post?

 

[Junior]

I suppose in a automotive application where the duty cycle is relatively low, one might see lower wear numbers due to the lower cylinder pressures and temperatures provided by lower oil pumping losses in the engine provided the oil is still thick enough to protect. But, I don't know that one would ever be able to measure the difference. I really don't know.

btw, I never used to be a believer in thinner oils and longer OCIs until I tried them.

 

[Junior]

I don't know that you would see less fuel dilution. The warm-up cycle should be about the same for both 20 and 30 weight oil.

If you use the argument I have heard on here about heiver oils running hotter, then maybe a thicker oil would be better for this. Then again, this close to a holiday weekend, I really don't know too much.

 

[Laminar Lou]

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I suppose in a automotive application where the duty cycle is relatively low, one might see lower wear numbers due to the lower cylinder pressures and temperatures provided by lower oil pumping losses in the engine provided the oil is still thick enough to protect. But, I don't know that one would ever be able to measure the difference. I really don't know.

btw, I never used to be a believer in thinner oils and longer OCIs until I tried them.

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That's what originally got me to buy the 0W30, because I thought the pumping losses when the engine was cold would be less (and this truck goes back and forth to work and home 4 times a day at 5 miles each trip).

However, I was thinking that since a thinner oil does overall increase the fuel efficiency it would also contribute to less wear over time as well. Unless the fuel efficiency is mostly gained in the warmup stage. I would guess that the 5W20 would be more efficient even at full temp, but maybe that efficiency is not as pronounced as the warmup efficiency advantage.

That is why I asked...

 

[Junior]

One really needs to look at the viscosity of the oil at the expected cold start temperature. For example, I believe, GC 0W30 has a higher viscosity at say 40-50F than some 10W30s and most certainly 5W30s.

IMO, There won't be much of a difference in start-up wear between a 5w20 and 5w30 in mild temps (say 40-50F on up) The more important question would be can the 20wt handle the additional fuel dilution and moisture accumulation and still provide potection during short trips? (and the occasional longer full operating runs) For the most part, from what I have seen here, the 20 wt can. Just my humble opinion.

 

[Max_Wander]

I'm susprised your mileage went down after the O2 sensor replacement!

 

[Steve S]

If the oil"film "is thick enough to keep the metal apart there won't be any difference in wear. There will not be enough difference in the gas consumed for your engine to notice. The start up wear won't be noticeable unless it is 20 below and the oil takes 5 minutes to build up pressure.

 

[Merkava_4]

I'm really beginning to wonder if there's that much difference in fuel mileage between 5W-20 and 10W-30.

 

[wileyE]

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I'm really beginning to wonder if there's that much difference in fuel mileage between 5W-20 and 10W-30.

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I've run penz 5/20 vs. troparctic 10w30 and dealer 10w30 in my accent, both winter and summer, no change in mpg whatsoever.

 

[Gary Allan]

Whenever I see someone (Bufford T. Justice comes to mind) say "more protection" ...I wonder "from what?"

If they said "more of a buffer in the case of some extreme condition where viscosity will make a difference" ..then it makes some sense. It ends up being a very heavy spare tire to carry around for no good reason. The concept works in some instances, but for most ..it's just a waste of energy for something you typically need not fret about.

Fuel economy differences, imo, are most effected/altered by warm up cycles/mile. Few miles per warm up cycle?...the more influence viscosity can play. YMWAV (your mileage will always vary)

 

[Auto-Union]

I see no mpg difference. I see no wear differece, my best guess is it depends on driving cycle and temps. Driving 90mph steady on the hwy or hammering it turn after turn in hot temps vs short trips in cool climate. People should be able to figure out what suits them on that point. On a final note, I think the final factor is do you want a fast revving engine or something smooth and quiet. Using GC in my Acura this summer. It's quiet, not so fast reving and I drive hwy.

 

[Curious Kid]

For some reason, I find myself erroring on the side of wanting to carry around a "full size tire" from spring to fall, as Gary put it. I find myself traveling 8miles to 40 miles, mostly level ground to some steep grades, from 25 to 75mph, just myself or w/trailer behind...the engine seeming to hover around 1.9-2.5krpm (3k in 3rd with trailer). Oil temp so far this year has reached above 210 deg.f as I have only recently started to monitor oil temps., though I have not done much in the way of towing this season. During the winter months, things wind down - trailer's stored, temps drop below freezing, and I travel mostly 8-10 miles one way to work...I'd be lucky to see the oil temp reach 190 degrees, and this has lead me to try a batch of 5w30 + 0w-20 this past winter (didn't notice all that much, though I must say that Castrol's HM 5w30 is on the thick side of things so in the end the viscosity may have come out to be just like a regular 30wt.?.

So, though I may not ask as much as others from the engine relatively speaking, I do try to enable favorable conditions for what ever may be embarked upon in terms of duty cycle conditions, in favor of getting what is hoped to a long, useful life from the equipment. If I could get better MPG, less strain on the battery and starter, and run cooler while still presenting the engine with favorable properties of essential input requirements under circumstantial loads, than I would be most pleased. there is such a thing as being overly confident if my memory serves me correctly, so...

I have wondered though for changing viscosities of oils, if that having varied viscosities at any one temp and how tmperature is also to be considered in terms of part(s) fitment, how might this related to wear? I suppose this is all like a dog chasing it's tail...wear is inevitable, and if lessened in one regione may equate to an increase in another. Fuel economy may take a hit and things may feel more sluggish. Piston rings and cylinder liners wear rates may increase while flat tappet valvetrains rates would decrease. Systematic/operational relations...a quandry.