Hi Scotty, Hope all is well,
I have a 2011 GMC Sierra 5.3L 2wd V8 Flex Fuel with over 200k miles on it(mostly highway). I recently started using E15 and found that the vehicle runs better with it. It seems to have a bit more power and it does not switch from V8 to 4 cylinder as much. It seems to stay in V8 mostly, idle quieter, and the computer is also reading better mpg with E15, however It seem be less mpg in reality(cpu reads 16.9 with regular and 17.2 with E15). My first dilemma is that I have be running it with regular fuel since 2011 and was wondering if the fuel switch would be harmful even though it's an E85 vehicle. My second dilemma is that the fuel comes from RaceTrac which is not listed under Top-Tier gas stations. My final issue is that I may have to switch or mix the E15 and E10 regularly because E15 is not available everywhere.
Would it be best to go back to regular top tier fuel and continue letting the engine switch from V8 to 4 cylinder regularly, or give the E15 a chance?
Thanks Scotty.
Antoine from New Orleans
You're allowed to use E85 since it is flex fuel compatible. That's why the switch to E15 was very noticeable in terms of power.
wondering if the fuel switch would be harmful even though it's an E85 vehicle.
No. It's designed foe it.
My second dilemma is that the fuel comes from RaceTrac which is not listed under Top-Tier gas stations.
Top tier gas has to do with detergents and keeping the engine clean. You shouldn't notice any immediate difference.
Would it be best to go back to regular top tier fuel and continue letting the engine switch from V8 to 4 cylinder regularly, or give the E15 a chance?
It sounds like the truck is more pleasant to drive on the E15, so I would probably go with that, but I wouldn't overthink it. The differences are probably insignificant.
Also be aware that AFM (switching to 4 cyl mode) will eventually destroy your engine. It's a good idea to have it removed if you want to keep your truck for a long time.
