how to determine which oil is most fuel efficient

[airbus]

How would I determine from looking at an oil spec sheet which one is the most fuel efficient versus other oil brands of the same weight (20 weight). For example, Mobil 1 0w20 (I know it is discontinued) spec sheet indicates "viscosity cst @40 53 and viscosity @100 is 9. Also, does the HTHS viscosity matter? Also, I am going to stock up on Mobil 1 0w20 oil since it is discontinued. I drive about 40,000 miles/year and my car has 165,000 miles on it. I am worried that I will end up with too thin a viscosity of oil in the next few years since my car may start to consume more oil as the engine starts to wear more and consume too much 0w20 oil. How long should I be able to run the recommended viscosity of 0w20 (5w20) before I have to move up to 5w30?

 

[Steve S]

Only time will tell,something to ponder ,probably the tires may make more difference and I wonder there is a list of tires according to rolling resistance/

 

[mikemc]

As mentioned above, you would have to run each oil in your particular vehicle to know for sure. I have gotten better mileage from some 5w30's than certain 5w20's in my Ranger. I would guess that if you are using more than 1 quart in 3K miles its time to move up to a thicker oil.

 

[Curious Kid]

I'm kind of supprised one is still able to use a 20w in an engine with such mileage without consumption/leak issues...that's great.

As far as going from a 0/5w-20 to 0/5w30 I don't think it will make much of a difference in mileage, as it could in helping to maintain the hydrodynamic state of lubrication. I'll admit to splitting hairs myself.

The subject of tires and rolling resistance is a good one. I can't say I have seen a tire guide listing rolling resistances to enable the vehicle operator to make an informed, technical choice.

Another thought to obtaining better mileage is if the street departments would work on the signal timing, and have them interconnectted between towns, in hopes of minimizing stop-go driving conditions. So many end-of-pipe solutions.