[78w72]

not all BP fuel has ethanol. here in iowa its required to label gas with ethanol, BP stations in my town dont have the 93 option that has 10%, we have straight 87, 87 with 10% & the premium is 91 octane with no ethanol. the straight 91 runs best in my 10.72:1 e-head engine but it can run on 89 & 87 like cliff mentioned but likes the 91 better. a few stations do offer the 93 with 10% like shell & kum & go & murphys (walmart) but BP & all other stations still have the straight 91 premium.

as for octane booster, 9 out of 10 off the shelf boosters are very misleading in how much they increase octane... the bottles say something like, will raise octane 3 or 4 "points." points are not whole numbers like most people think, its 10ths of a whole number, so a bottle raises octane maybe .3 or .4, itwould take 3 bottles to gain 1 whole number. waste of money in my book if you have to add that much booster to every tank just to be able to drive the car without detonation.

& run on doesn't always mean there is detonation or a timing issue, i had some run on the hottest of days or after the gas got to be about a month old, but turned out it was carb/idle speed settings. ive had cliff do 2 carbs for me & initially just bolted them on out of the box, set idle speed & drove. they both ran great except the rare occasion of run on in the e-head motor... i eventually lowered the idle speed as much as possible then tuned the mix screws to get most of the idle speed back. idles perfect at 750 now & has zero run on or detonation with almost 11:1 & 89-91 octane & NO octane booster.