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Hi: A couple of Questions about the gas up here in Canada! 1) Thinking of using mid-grade 89 octane on my 2.5L GT Turbo & when going on trips to Toronto or else where using 91/93 is this a good plan?Thanks. 2) Which gas is best to use out of the major companies (Shell,Esso,Petro Canada?Thanks for the help!!!
 

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Not a direct answer to you... but on the Left Coast we have Chevron gas stations that sell 87, 89, 92, and 94 octane. Chevron actually produces only two fuels, 87 and 94, but blends in the pump to end up with the four above-noted grades. 87 octane has (up to) 10% ethanol, and the 94 octane has zero ethanol... so the blend you get also determines the % ethanol. I don't particularly like ethanol... it perishes fuel system rubber, and I am told it is corrosive. Also, an engine on ethanol has poorer fuel economy.

Me, I like the higher grades (which BTW are pretty expensive and probably not great value) - but with a direct-injected engine it is my contention (and note, "YMMV") that one way to lessen motor oil fuel dilution is to run a higher octane grade fuel. The logic module does either an ignition retard or a fuel enrichment (actually, likely, a combination of both) when the knock sensor or the "map" hears or predicts pinging... and if you run a higher grade fuel, the propensity to knock for any given condition is less... and it MAY mean that the mixture richening action is lessened (and fuel dilution is lessened). Fuel dilution is worse with short-hop driving, and in cold weather (though it seems counter-intuitive (from a prevention-of-pinging perspective).. as the engine is cooler and therefore pinging ought to be less). Of course cold engines need fuel enrichment.

Some fuel dilution is tolerable, I'm told (Blackstone Labs / "BITOG" says up to 2% is OK) - but I abhor the idea... lessening the viscosity of 0W-20, which just by being in service, lessens anyway. Maybe just my own mania, though.

I should mention that some of the folks here have run 87 octane and 0W-20 motor oil in their 2.5 Skyactiv-G and have not seen appreciable fuel dilution (to the extent that their oil analysis Co. has a quality /accurate process for measuring fuel dilution) and notably have not seen wear materials of any import show up in their used oil analyses.
 

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Use Shell 91. It's the only fuel in all of North America that is ethanol free. You will notice better performance and efficiency. Plus it's got lots of detergents to keep your engine/fuel system clean. Helps your car run really well too.

Second choice is Petro Canada. It has ethanol in it, but it's still really good fuel. I've been going out of my way using exclusively Shell 91 fuel in my BMW for as long as I could remember.
 
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