Hi all:
My Corolla specifies 87 octane or higher. I like Shell but their highest additive concentration is in their high octane (91 here in Colorado). I wrote to them and they said 87 octane (the next step down here in Colorado) has 50% the additive concentration of the 91. Someone in a recent thread said that higher octane fuels if not required by the engine "dirties up" the engine or something like that. Is there any truth to this? I was considering periodically using the Shell 91 octane in the car purely for the higher detergents.
My Corolla specifies 87 octane or higher. I like Shell but their highest additive concentration is in their high octane (91 here in Colorado). I wrote to them and they said 87 octane (the next step down here in Colorado) has 50% the additive concentration of the 91. Someone in a recent thread said that higher octane fuels if not required by the engine "dirties up" the engine or something like that. Is there any truth to this? I was considering periodically using the Shell 91 octane in the car purely for the higher detergents.