With high gas prices, one of the questions many riders are asking is if they have to sue premium fuel. To answer that, we have to take into consideration the exact sled and engine set-up. If you’re running any form of higher compression, then chances are you need the slower flame front speed afforded by the premium fuel. But, this depends on the elevation. Generally, as the elevation is lower, as the compression is higher and as the ignition timing is advanced then your octane requirements are increased.
Using premium fuel in a sled that doesn’t have advanced timing or higher compression actually will take power away from your package. Arctic Cat has been telling their F-series riders for the past few years that the stock set-up is designed to work with 87-octane fuel, and that the sleds are faster on it.
First you know if your sled has a knock sensor. If it does, then it can likely compensate for the various fuel types and adjust the ignition timing accordingly. Most of the newer generation of CFI and SDI engines will have this, so they will run at full power on premium, but will roll back the timing slightly if a lesser octane fuel is detected. Many older Polaris models have a key switch that can be set manually to premium or regular, so you can run whatever you want in them. The Arctic Cat four-strokes make more power on premium, but can sense and adjust the timing for 87-octane fuel as well. All of the Yamaha four-strokes, with the exception of the Phazer, prefer to have 87 octane fuel. The Phazer can handle the lesser octane, but will sacrifice some power in the process. Most days you’ll never notice the difference.
What about sleds that say right on the fuel cap “premium fuel”? Does it say “required” or “recommended”? There is a difference. Most every sled that says “recommended” will be perfectly fine on 89 octane, but they’re just a little closer to the “edge”. We’ll even run 87 through them, as long as it isn’t a full tank of it at once. With these sleds, be weary of high-load conditions like wet heavy snow or long high speed runs. Give it a splash of 89 to make sure your 87 is good enough, as some gas might not be 87 like the pump says, and then your safety margin is all used up.
During the 2007-2008 riding season, we ran 89 octane fuel pretty much all year long in all of our sleds. With the Ski-Doo 800R PowerTEK, we would run 89 and 87, trying to keep the fuel in the tank always at something higher than 87 octane fuel. Same thing with our 600 H.O. E-TEC, it said “premium fuel recommended” on the fuel cap but we ran 87 and 89 for thousands of miles. We never had a problem all year long with any of our sleds. Personally, we run 89 with confidence and would alternate between 87 and 89, just to make sure what we had in the tank was always higher than 87.
Again, if you have a higher compression head, or an aftermarket pipe, then you should consult with your speed shop or go-fast parts supplier to find out what they have learned what works best in their set-ups and what they suggest. Mountain riders who traverse large elevation changes and bump up the compression levels to compensate for the higher elevations are at higher risk, especially when they come down the mountain.