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#150729 - 03/26/08 08:22 AM Supercharged engine...mid or lowgrade petrol
Syracuse Offline
Junior Member
Registered: 11/14/05
Posts: 16
Loc: Syracuse, New York
With the price of gas flying higher than a kite has anyone out there considered running a lower octane in their supercharged GT/GTP?

My brother owns a Chevy Silverado with the V8 in it and he runs on 87 and gets all the power and performance he needs.

IF, and this is a BIG IF, I were to run on a lower grade fuel - what preventitive maintenance should I plan on doing to keep the engine from getting build up of garbage from not running on high-test.

"Soon to be broke in Syracuse"

Thanks!
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#150730 - 03/26/08 12:18 PM Re: Supercharged engine...mid or lowgrade petrol
AustinGTP Offline
Member
Registered: 05/23/03
Posts: 8078
Loc: Austin, TX
The difference between a fill up on low octane vs high octane is only about $3.00. Most find it beneficial to go ahead and spend the extra $3.00 per 13 gallon fill up.
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Bobby

Died 5/1/08, resurrected 5/15/08
ASCD SD hood, 17" Bullitts, Overkill PCM, 3.4" Pulley, NGK TR55IX, K&N 9" cone filter, JimmyC D/P, U-bend removed, Flowmaster 40 series, Hooker big bore tips with resonators, S/B brake lines, drilled/slot rotors, GMPP handling kit, KYB struts, F&R strut supports, HID's, LED's, 2.5" Air Dam, red GTP overlays on custom badges, white rear insert.
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#150731 - 03/26/08 05:43 PM Re: Supercharged engine...mid or lowgrade petrol
ordonez1307 Offline
Member
Registered: 04/18/05
Posts: 8901
Loc: Bradenton, FL
keep running high test. for your pistons sake
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#150732 - 04/02/08 01:55 AM Re: Supercharged engine...mid or lowgrade petrol
Arcxnus Offline
Member
Registered: 04/05/05
Posts: 1921
Loc: Texas
A Chevy Silverado isn't supercharged.

Don't run lower octane just to save a few bucks when later down the road it'll lead you to paying a grand or two for a new engine when you pop a piston.
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Quote:
Originally posted by HercMan:
Sounds like corrosion has had it's way with your nuts.
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#150733 - 05/03/08 05:23 PM Re: Supercharged engine...mid or lowgrade petrol
DenverGT Offline
Member
Registered: 08/29/06
Posts: 74
Loc: Denver, CO
Higher octane isn't to make more power... in fact in a car designed for lower octane fuel, higher octane will actually decrease performance.

The higher the octane of a fuel, the more it can be compressed before it will self ignite.

The L67 motor in the supercharged GP is designed for higher octane fuel. It's compression is fairly high, and with the supercharger, it's very high. If you use lower octane fuel, that fuel will ignite in the cylinder before the spark plug fires. This causes knock. The PCM will attempt to adjust timing, but with very low octane fuel, it can't eliminate this knock caused by the fuel igniting early.

That knock is actually the fuel igniting while the piston is still moving upwards, trying to compress the mixture. This creates tremendous stresses on the piston, and can blast a hole right thru the piston itself.

It MIGHT be safe to run lower octane fuel if you were to remove the supercharger belt, as the compression without the supercharger will be much lower.

But assuming 20 cents extra for the good stuff, you are only talking $3.00 extra per fillup. Is it worth the trouble to use the lower octane fuel? You can easily save more by just driving a little slower, not punching it off the line, etc.
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