104 or 110 0ctane
Uber Waxer
Joined: May 2004
Posts: 8,651
Likes: 5
From: Hanover MD
Cruise-In 8-9-10-11 Veteran
CI 9, 10 & 11 Car Show Winner
St. Jude Donor '08-'10
it will kill your o2 sensors and probably clog your cats. most of the 104 and higher octane are leaded. there are some unleaded ones around 104, but any higher requires lead. and unless your car is tuned for more octane, it would be a waste.
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Burning Brakes
Joined: Jul 2007
Posts: 798
Likes: 207
From: Rougemont NC
Complete waste of money. I'm part-owner of a high performance motorcycle shop, where we do tons of dyno-tuning and fuel mapping. You want to use the lowest octane rating as possible, without having any pre-detonation issues. As stated here previously, the higher the octane number, the less explosive the fuel is, (i.e., less power) again, to prevent detonation (spark knock) issues. 93 Octane Unleaded is perfectly fine in your stock C5. Just use a good quality gasoline, and add a bottle of Techron gas treatment from time to time, to ward off the dreaded fuel sensor problems that are so prevalent on the C5's.
Le Mans Master
Joined: Jun 2006
Posts: 6,979
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From: Wichita KS
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
If all you have is 91 in your area mixing about a quarter tank of unleaded 104 wouldn't hurt. Other than that save your money as stated earlier!!I run midgrade in place of premium in my motorcycle at the recommendation of the dealer and it runs fine!
Race Director
Joined: Apr 2007
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From: Ideals are peaceful...History is violent...St.Charles, MO.
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St. Jude Donor '08-'09-'12 thru'22
Spend your money on a mod that will make a realistic difference and net you some return.
