One of the more frequent questions is if you own a Ski-Doo E-TEC and can’t find premium 91-92 octane fuel while out riding, are...

One of the more frequent questions is if you own a Ski-Doo E-TEC and can’t find premium 91-92 octane fuel while out riding, are you better off adding some form of octane booster or can you run 87-89 octane fuel? How safe is it to do so?

According to Ski-Doo, you are better off to use the 87 octane fuel than to add octane boost. Recently it has been found that the use of certain types of fuel additives, including octane boosters, in the E-TEC engine may increase the risk of fouling a spark plug lead to a loss of peak RPM. The engine RPM was reported to be limited to around 7100 rpm. The low end power was normal but the RPM would flatten out at around 7100 RPM.

It was discovered that the spark plugs were “lead fouled” from the use of leaded fuel or additives containing lead, which become conductive over the firing tip. When the temperature of the spark plug increases the conductivity of the lead compound formed on the spark plug surface increases, causing misfiring, this explains why the engine performs normally at lower RPM. This is often observed when using Aviation gas.


Sometimes the lead-fouled spark plugs can be identified by looking at the spark plug itself, as the ground electrode may be coated with a Brownish-yellow or Pinkish-red glazed coating. The only solution is to replace the spark plug.

Both the Ski-Doo 600 E-TEC and 800R E-TEC engines are calibrated to use 91 octane rated fuel. If premium 91-92 octane fuel can’t be found, Ski-Doo recommends using 87 (or 89) octane fuel without adding octane booster additive. The E-TEC engines are equipped with a knock sensor, so when 87 octane rating fuel is used the ECM will monitor a higher knock level and automatically switch to a safe calibration. No damage will be created by temporarily using 87 octane rated fuel, however a slight loss in performance will be observed. This is due to the ECU retarding timing and slightly richening the fuel delivery, so you might also notice a slight decrease in fuel economy.

Reprinted from the December 2012 issue of SnowTech magazine. Published November of 2012.
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  • R Desaulniers

    February 15, 2015 #1 Author

    I bought an Expedition 600 E-TEC in the spring of 2014 and was always intending on keeping a bottle of octane booster just in case I got in a situation where I needed it. Or so I thought before I read your article(now end of Feb. 2015). I’m glad I didn’t do it… This article also most likely explains why we needed to replace spark plugs so often back in the days when lead was used as an additive to cheaply boost octane in automotive gas. Thank you very much for your post witch makes very much sense.

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