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  • rickmn 05/06/08 11:03 pm PST

    If you put in a lower octane, the engine will have pre-ignition (ping). The knock sensor will detect that and retard the timing. That will decrease your pickup and gas mileage. The lower octane can also cause misfires which will set off your check engine light. The misfires load the catalytic converter with unburned fuel which causes it to run at much higher temps, which can destroy the converter.

    Need any more convincing?

  • actualsize 05/06/08 11:10 pm PST

    When an owner's manual states that 91 octance is required, then that's pretty much it. Engines like this do not tolerate lower octane fuel well. Over time, damage can result that will be far more expensive than the fuel cost saved by using a lower grade.

    There are cars that merely recommend 91 octane. Cars like this have the ability to run on a range of octanes (a minium is usually specified regular 87), but the horsepower and 0-60 advertising claims were made using 91 (or in some cases, 93). So they recommend that fuel for best performance. The new Cadillac CTS is such a car.

    Ethanol doesn't enter the picture unless you have a flex-fuel vehicle, which you don't. A lot of specific mechanical and engine mapping software considerations go into a flex-fuel engine.

  • obyone 05/06/08 11:16 pm PST

    One thing to remember is that warranty issues that are engine related will bring up questions on the type of fuel you're running. If the dealer gets wind of anything other than premium you're going to have to do a lot of explaining and will probably still be denied warranty coverage.

    Second point. Manufacturers understand the cost of fuel if they could give you performance that you want with the G35 with regular I'm sure they would've.

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