My marina only has enthonal free 90oct and I can get 102oct race fuel ,just trying to do the math and want to come up with the correct mix to make 93oct gas. So 1 gallon of 90oct to ? 102oct.

Here ya go

http://ranney.com/mjr/fuel_blend.html

http://members.cox.net/ftraycing/octanecalc.shtml

to get to 93 octane, use 25 gallons of 102 for every 75 gallons of 90

Ok got it, Thank you.....

If I did the math right, 3 gal of 102 + 7 gal of 90 = 93.6

Is the 102 a bulk tank fuel or is it 55gal drum qty? If it is, might check with the supplier and find out the specific gravity of the 102. If its a branded fuel like "turbo blue" or something, it may be a little lower SG than the 90. It will initially mix up just fine for about 7-10 days then will definately stratify (seperate layers)...

Not an expert, just a chemical blender familiar with SG's and blending..

If your engine is designed to run on 93 octane and you mixed the fuel and ended up with a higher octane say like 95 or 96could it actually hurt anything?.....would it hamper performance?

I was just going to pick it up from Sunco station and fill a big 20 gallon fuel tank up and the put the 90octain in at the marine.

Call down to the station and find the name of the fuel. Sunoco lists all their SG's in PDF form..