What type of fuel does the stock 2002 (1975) prefer?
im gonna look cuz im curios what bmw reccomended in 75.i would run 89.may not have any issuse with 87 and def can run 91.but im gonna look to be sure.
The quality of gas has changed a good bit since 1975 so I would just try a tank of 87 and see how it behaves. If it starts to throw a fit then dump a bottle of octane booster in it and try 89 and keep raising the octane until it runs well Or you could pick the octane level you want to run and tune your carb and ignition timing to match. A full tune up (including carb, ignition timing, and valve adjustment, cap, rotor, plugs, and air filter replacement) can make a very noticeable difference. Nice car by the way. The older BMWs get the more I like them.
I have faithfully used 87 octane. I have no issues with weber carbs, oil smoke, nor any knocks, pings, or stutters. I run midgrade in the 1988 735i, have never tried the 87 in it.