[mwebb]

87 octane fuel is the correct choice
any fuel with a higher octane does not combust as well nor will it provide as much FE as 87 octane in your system .
as an added benefit , higher octane fuels will leave more deposits behind due to incomplete combustion in your engine .

do not advance base ign timing beyond where you have it , peak combustion pressure must happen at about 14 degrees after TDC , every degree your base ign timing is changed also changes
peak combustion pressure timing by that amount .
your system does not have feedback for ignition timing related to ping .

see
Top Tier Fuel
any retailer from the list in that link is the best fuel you can buy UNLESS you have a source for E0 , compare FE results to see which brand from the list yields the best FE for your system ,
let the FE test results guide your purchase habits

the only fuel additives that work are Chevron Techron and BG44k
they are the same thing
chevron techron is cheaper

Originally Posted by Georgboy

Okay well finished up the tank of mid grade chevron (89) . XFI cam,timing set at around 6 deg adv.. The cam has improved mileage around 3 mpg.. Which gas is better? Chevron or shell? I am thinking of advancing the timing to around 9-10 and run premium (93 octane) .. Just curious if my CPM would stay around .06 ..... What do you guys think?