Would use a synthetic such as SHELL full synthetic , Pennzoil Platinum or Mobil 1 . Calls for 0w-20 in owner manual , but was given the o.k by Honda customer relations by email . Thanks

 

If you want a little less mpg i guess sure go ahead. I don't know your argument why you wouldn't use 0w-20. Honda even back approved it to be used on models '02 and newer minus very high revving motor in S2000 and RSX-S.

 

Technically, it shouldn't matter if you're running 5w20 or 0w20 as far as gas mileage. The viscosity is the same at operating temperature. There is no benefit to running 5w20.

With 0w20 you get better lubrication at startup, when most engine wear occurs.

The only reason I see running 5w20 is if your favorite oil does not come in the 0w20 variety... I know some performance oriented oils are like this.

If you are concerned about viscosity breakdown with elevated temperatures (like racetrack conditions, not "it's hot outside today") you'd need to run a 30 weight to make a difference at operating temperature.

There is no difference in the motor between 09-13, just the recommended oil changed, probably because 0w20 became more readily available.

 

You can use 15w40 if you want, but you're best off using what it actually calls for. With oil change intervals on these things being what they are, you've got plenty of time to find the right stuff.

 

where do you find this change in gas mileage?

0w-20 and 15w-20 will perform the same even.