Ask the Automotive Repair Expert – Jamie Senior

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Ask the Automotive Repair Expert – Jamie Senior


Many of us were taught to use a higher octane fuel when we wanted to “treat” ourselves to a little extra power. With modern computer-controlled engines, choosing among regular, mid-grade and premium gasoline is more complicated than that.

The octane rating is expressed by a number like 85, 87, 89, or 92. The higher the number, the more resistant the fuel is to premature detonation. As the fuel and air is compressed in the engine, it can explode before it is supposed to, which isn’t good. Your vehicle manufacturer has a recommendation for the proper octane rating to work with the way your engine is designed. This number is indicated on a sticker by your gas cap.

General Rules:

  • Never use a lower octane rating than recommended by your manufacturer. This can lead to engine damage over time.
  • Using gas with a higher octane rating than recommended in most modern vehicles will not deliver any significant advantage in terms of performance or fuel economy. Simply put – it isn’t worth the extra money.
  • Some engines, usually in high-end luxury and performance cars, are designed to work with two octane levels. The manufacturer will state a horsepower output for each of the two ratings. They accomplish this with additional sensors and computer controls that aren’t found in most vehicles.

Manufacturers are building more and more high-compression-ratio and turbocharged engines that require high-octane rated fuel to deliver the power and durability that was engineered into the engine. Bottom line: saving a few pennies on a litre of gas can turn into a big expense down the road.