On your back arm ? I doubt that <| sep |> A random search pulled up a perfectly explained answer from umightypenguin . . I ' m telling you this so you can understand fuel and your car better . Next , Premium vs Regular is not different quality , or better or worse quality gas . That more depends on the station or where the station gets its gas from . The difference between them is Octane Rating . Octane rating determines on how quickly and evenly the fuel will burn when its in your engine . Lower octane gases ignite and burn quicker than higher octane will . What this means is that depending on how your engine is tuned , what the timing is , and how hot it is , it may be better to use premium so that the fuel does not ignite too early in cycle . downsides can be less power , mpg , and in more serious cases , engine knocking and valve chatter from fuel not burning right , this can damage the engine All things considered , it ' s probably not a big deal , if your just cruising or driving easy its not gonna hurt anything . But the things I mentioned certainly become more relevant when driving with the engine hot , and at high rpms where there is less tolerances . Just go to an auto store and buy a bottle of octane booster to throw in the tank if your worried about it or going to drive it hard . If you drive like a grandma or normally then just keep driving and you ' ll be fine . I know a lot of the things I said can make it sound serious , but honestly unless your driving a highly tuned car , or have an engine with other issues , its really no big deal . Me personally ? I would over look the car with a fine tooth comb for any other issues . If this is the only issue I personally would be ok buying the car . If you see other issues like oil build up and running hard . I would avoid it