How many different types of gas were available in 1991?

LOL Who is your mechanic? There was leded gas back then (in addition to unleaded)

87, 89, and above octane levels were available in 1991. That car should run just fine on 87 (regular) octane fuel. If you want to be sure, just check either inside the drivers door, or on the gas flap to see what the manufacturer recommends in terms of the "type" of gas to use.

i know i couldn't get leaded gas here, but it shouldn't run leaded anyways. most states have banned leaded gas by then.

If it doesn't knock on 87 unleaded going up a hill (under load), then that is fine. If it does, use the 89. Your mechanic doesn't know what he's talking about in regard to fuel types.

there's nothing fancy or spectacular about your galant. run regular unleaded gasoline in it and every oil change add a bottle of fuel injector cleaner. but fyi, back in 1991, there was 87, 89 and 92 octane gasses for purchase and also 100 and 110 octane for racing, all of which is still available. Tell your mechanic to get out of the 60's. Using a high octane gas in an engine NOT designed to utilize it can potentially create a carbon buildup in the engine, and also cost you $.40 more per gallon at the pump.

High octane gas equals better performance. I don't know if your car is a sports car or a family car but, if you're not doing anything Fast and Furious I think regular would be fine.

sorry

id say there were four ,leaded , regular unleaded, premium ,and diesel.