Better milage with 5w40??

[Camprunner]

I have a strange one so here goes I recently switched to Shell Rotella Synthetic 5w40 in my "06" V6 Toyota 4runner and im getting on avarage between 19.5 to 20.0 miles per gallon with around 800 miles now on the oil. Now for the strange part for the first 53,000 miles on the truck I was running 5w30 in either Penz-Plat or Shell full Synthetic and getting between 19.0 to 19.4 miles per gallon but never over that. My driving style did not change and im driving the same combo of city plus highway.

Why would I be getting better milage with the heavy oil? I would think it would go down not up?

 

[simple_gifts]

100's of variables determine gas mileage; oil weight is just one (small one), and although you tried to control some of the others, there are probably too many uncontrolled to be conclusive.

 

[Camprunner]

I was thinking about this as well I think I will give it a few changes to come to a better opinion.

 

[glennc]

One conjecture:

Your tires have worn somewhat since the last time you really paid attention, adding 1-2% to you mileage. You have had slightly more favorable weather conditions on average, adding 1% to your mileage. You have driven just a smidge more gently, despite trying not to, because you are excited about getting better mileage, adding 2% to your mileage.

Unfortunately, your oil change reduced the mileage by about 0.8%, but that change is overwhelmed by everything else, and the end result is a noticeable overall improvement.

 

[Merkava_4]

Originally Posted By: Camprunner
Why would I be getting better milage with the heavy oil? I would think it would go down not up?


Because that oil at that viscosity makes for better lubrication for that engine period.

I'm not surprised in the least.

 

[Audi Junkie]

Better compression with thicker oil vs lowered pumping visc.