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Regular or Premium: would this ruin it?

  1. Oct 27, 2004 #1
    My dad just bought a car and he decided to use a premium gasoline instead. The car uses regular at the moment, if premium is mixed into it would it somehow ruin the engine? long term wise is this a bad thing?
  2. jcsd
  3. Oct 27, 2004 #2


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    No. The cars with EFI (electronic fuel injection) have electronic computer controlled ignition systems as well and monitor if something like detonation, which premium helps prevent, occurs and adjusts the ignition to match. Most cars will show no benefit to running premium but some will make more power (because the computer can run a more aggressive program) and they are usually labeled as such (Corvette, Porsche, etc).

    Most cars are designed to run on regular. Car & Driver tested a couple cars like an Accord and M3 on a dyno. The Accord actually lost a tiny bit of power on premium (but within margin of error so insignificant) and the M3 only showed a tiny gain but had other issues running on a dyno because of its programming.

    On older cars, this is different because of different designs of engines and materials. If it were a late 60's muscle car its premium and lead additives to keep that thing happy.

  4. Oct 27, 2004 #3
    Detonation, pre-ignition, and octane ratings


    You might want to point this webpage out to your dad:

    • What does octane mean?

    Sport Compact Car had a better article on octane a few years ago, but I can't find it at the moment. Helpfully, it pointed out that most articles on octane claim that the major problem is pre-ignition (igniting before the spark plug fires, as the above article from HowStuffWorks mentions) when in fact pre-ignition is responsible for only a minority of the bad ignition events in an engine running on too-low octane. IIRC the article in SCC said a majority of the bad iginition events occur after the spark plug fires. There are supposedly two types of post-spark events, but this article mentions only one, detonation:

    Added quote tags
    Last edited by a moderator: Oct 27, 2004
  5. Nov 1, 2004 #4
    This is very interesting. Thanks Cliff_J and hitssquad
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