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Old 06-03-2003, 04:31 PM   #1
Scooby Newbie
Member#: 13666
Join Date: Dec 2001
Location: Eau Claire
2004 STi

Question gas for the sti?

I read past information relating to octane and use of ethanol and am still confused. I can get 91 octane gas without ethanol and 93 octane with ethanol (10%). Which would be the better choice of the STi?
soma is offline  
Old 06-05-2003, 09:06 AM   #2
Scooby Newbie
Member#: 36575
Join Date: May 2003
Chapter/Region: E. Canada
Location: Ontario, Canada
'04 STi

Default Octane

I'm not a fuel expert, but I've read numerous articles on this over the years. At 10% Ethanol, there should be no harmful effect on the motor, only a positive effect on emissions.

Most people say that using any octane rating above what the manual says is a waste of money. However, if the car sits in the garage for a week or two, the evaporative nature of some molecular components in gasoline results in a a loss of octane rating.

High compression and turbo engines need high octane to prevent knock. Higher octane gasolines require more refining (resulting in higher cost) and therefore may have fewer impurities.

I don't know how it is where you live, but here in Ontario, if I fill up with 94 octane versus 91 octane, the price difference is $0.02 per litre. With a 50 litre fill up, for 50 weeks of the year, I end up paying $50 more per year for a gas that is more robust to knock problems, and possibly more refined.

In the end, it's your choice.
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