Edmunds Answers



  • karjunkie 07/24/09 1:39 pm PST

    Modern cars have sophisticated knock sensors, so you will not damage the engine if you use regular gasoline. The engine's computer will just retard the timing and you will get reduced performance and probably lousy gas mileage. I suggest you try the intermediate grade of gasoline at your next fillup and see how that performs. If you notice no change you can stick with that. That is what I do. My experience with my BMW was that I can use regular in a pinch but the car does not run optimally and I get terrible gas mileage.

  • carbuff50 07/26/09 12:24 am PST

    We have a 2009 C300 sport and have only used regular since we bought it. It seems to run great and we just returned from a 1200 mile trip with a lot of hills, 110 degree heat (so the air was always on), car was pretty heavily loaded, etc... Maybe it is effecting the mileage but the mileage seems fine to me. Hope that is helpful.


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