Generally the highest I can find, 91/92/93. I used to be a strictly Hess guy, I've been upset since they left the market.
An experiment I ran with Sunoco 91 vs 93 showed more improvement in mileage than increase in price. I'd think that would be the case with an advanced design DI Turbo like the M274 which could make use of the increased ignition retardation.
An experiment I ran with Sunoco 91 vs 93 showed more improvement in mileage than increase in price. I'd think that would be the case with an advanced design DI Turbo like the M274 which could make use of the increased ignition retardation.