def winter gas. as far as SC, i still run my 91 tune on 93 gas and havent noticed any difference. it still chirps tires when i want and i dont here anything odd in the engine or feel any lag. my mileage around town is around 7 and 15 on the highway. but as far as the spark plugs go if you have never changed them i would def do that soon. ngk 5306 and stock size wires from bvd. there are 16 so make sure you have a few hours to tackle the job.