I'm reading all the BMW specs of LL17FE vs LL01 vs LL04. New BMW engines wanting 0w12 down from 0w20 and before that 5w30/5w40s. So my question is with such a hard push to these light oils what is the real mpg gain? People say it's all because of CAFE laws but what kind of MPG difference would I see if I went from a 5w40 to say a 0w20?
How much does oil viscosity really change mpg?
- Thread starter FlyingTexan
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Some people think that the fuel economy gain is just a cover story and that there really is no gain or benefit. Some even believe you can go from 0w8 to 0w40 in a new Corolla and you get a quieter better running engine with zero fuel economy impact. The crazy conspiracy guys think the real story is about reducing the lifespan of all gasoline engines on the planet, forcing you to buy electric. But we wouldn't talk about such things around here because we'd get in trouble.
It depends on ambient temps and engine.
Not too many folks here have the lab equipment and qualifications to run the kind of tests required to accurately measure the small differences in fuel consumption. Instead we have to rely on published data, conjecture, and anecdotes.
I would look to published scientific papers to see what information is available.
I would look to published scientific papers to see what information is available.
But proof is how long they last at the recommended viscosity. Somehow they will always say they know better than another. The majority follow the recommendations. Even the military has reduced viscosity with little regard to CAFE laws and had not taken a hit on reliability. New engines are designed from the ground up optimized for lower viscosity. Oil pumps with variable pressures controlled by ECU.
I've went from 5w20 to 0w40 in some vehicles and I can't say I got a measurable difference. I always calculate my fuel economy. It's less than half an mpg at best so I don't think I can say there was an actual difference that was the oil viscosity change for sure.
BMW reported around 3 percent when moving away from LL01/LL04 to iirc LL01 FE. The push is based on tighter emissions and fuel efficiency standards as all automakers are moving towards lighter oils. Lighter grades do have approvals with a fuel efficiency component.
btw..20 grades were in mind during development of the b-series engine family. Features include IROX coated (polymer) bearings and changes in the flow of oil through the bearings, electronic rather than oil actuated VANOS solenoids.
Research Shows Oil Viscosity Affects Fuel Economy
You could save as much as 1 percent on your fuel economy simply by switching from a 15W-40 engine oil to a 10W-30 engine oil, according to new research from Chevron Oronite
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Somewhere I read an interview with a Toyota Engineer around the time they went from 0W-20 to 0W-16 it was like 2-3%. I wish I saved the interview.
3% is rounding error to an individual - but huge for CAFE on a fleet. Its for them, not for us.
3% is rounding error to an individual - but huge for CAFE on a fleet. Its for them, not for us.
Can you show where any facts were posted? That's the entire point of asking. I asked for something factual, it's in the title, and i get conjecture.
Without a standardized laboratory test there is no way to come up with a representative value for everyday driving. It’s also highly dependent on the actual HT/HS difference, looking at the grade is pretty vague. Everyday driving is a seriously chaotic environment that buries even otherwise statistically significant variables in the noise.
But there is no doubt it makes a difference. No automaker would spend the money they do of it were corporately meaningless.
There is a benefit. If let's say the mpg increase is 1% in 0W12 over LL01, the point is, what are savings on tens of thousands of cars? It is not about individual savings but fleet savings, as CAFE has in its name. It is OK policy.
However, if the goal is to limit emissions, a far better option is just to ban the remote start option or aftermarket options. 0W12 cannot reduce emissions as much as preventing my neighbor from idling Dodge RAM with Cummins for some 30 minutes every morning just so she can drive to her work, which is 3.7mls away.
I remember old research said from 10w30 to like 5w20 is at most 1.5% (that's constant highway). In lower speed or traffic definitely nothing close to it.
Going from 5w20 to 0w20 is probably near zero.
Going from 5w20 to 0w20 is probably near zero.
I went from 5W-30 to 5W-40, to 0W-30 and 20W-50 Red Line. The latter is about as viscous as we can get. I didn't notice any difference, in fact the run with Red Line might have been my most economical ever.
So I would say it's all in the noise, just know that the difference is there but we're talking 1-2%....
You showed up in his thread - trolled him, gave a non-answer, and now, you’re bickering, filling his thread with useless posts that still do not answer the question.
Weird, my neighbor does this too.
Ironically, so does mine. She works 0.6 miles away, has a big V-8 Infiniti SUV, and idles it every morning for at least 15 minutes. The best part? She considers herself an environmentalist and has a flag in her garden that says, “tree hugger”. I kid you not.
For the OP - statistics apply to groups. CAFE economy gains from oil viscosity changes work for large numbers, statistically significant sample sizes. You, your vehicle, and your driving are unlikely to be able to prove a difference one way or the other.
The B58 was still specced with the LL01/LL04 initially. Maybe the grades were in mind but I find it hard to believe, and the only reviews I can find show, that a 0w20 is good at protection as a xw40
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