Originally Posted By: kingrob
A high octane fuel in an engine that doesn't need it could actually have adverse effects in terms of gas mileage. On my old Sentra I would run 93 BP and get poor mileage. 87 was ok, but my mpg peaked using 89 octane.
Perhaps, as I've pondered this before, with a reputably powerful detergent pack suck as V-Power Shell and Amoco/BP Ultimate, if the cleaning agents are loosening up deposits quicker than normal and your mileage suffers while it's burning off crud? I know that it's been said that you need at least two or three tankfuls of premium for it to make a difference, but on used cars I've purchased with a neglected fuel system I can notice the difference within about twenty or thirty miles of driving after a fill-up.
If your reply is directed at me, my engine and specific software call for 92 with a bare minimum of 89, so I am not not running greater than required spec. I also run FP+ in every tank, SI-1 once in a while and ARX maintenance dose - no crud anywhere in sight
My engine simply doesn't like my locally available variety of V-Power as much as other fuels. This is a 1998 BMW with an M52 engine over-maintained by an enthusiast. Esso comes out on top in terms of performance and economy, Sunoco Ultra 94 or 92 have good performance but poor economy, V-Power has poor performance and poor ecomony. If there was a contender with poor performance but great economy I wouldn't run it - performance is also important to me.
I do use V-Power in my OPE in general, however, to avoid ethanol.
