[BlackFastAttack]

Looking for opinions here. I would rather run the 93 octane performance tune than the 87 octane version. Despite what Ford claims, is there really a risk to running higher octane gas? Has anybody experienced a carbon build up problem or concerned that you might be??

[65sohc]

I think it is very unlikely that you would get more carbon buildup with higher octane. If anything some companies put a more effective detergent package in their higher octane blends, or at least they did in the past. I'm sure Ford specifies at least 91 octane for the Shelby and I don't think they are concerned about carbon buildup there. I don't have complete faith in any gasoline to eliminate buildup so I dump a bottle of Redline fuel treatment in my tank periodically for insurance.

[ski]

The concern about carbon build-up relates to using higher octane gas in engines that are designed to run on lower octane without installing an aftermarket performance tune. In this situation, the higher octane gas may not burn completely because either the engine's compression is too low or its timing is too retarded, and thus carbon deposits can accumulate.
But with an aftermarket performance tune the timing is advanced which allows higher octane gas to burn more completely, and thus prevent carbon build-up.

[pikapp]

Originally Posted by ski

The concern about carbon build-up relates to using higher octane gas in engines that are designed to run on lower octane without installing an aftermarket performance tune. In this situation, the higher octane gas may not burn completely because either the engine's compression is too low or its timing is too retarded, and thus carbon deposits can accumulate.
But with an aftermarket performance tune the timing is advanced which allows higher octane gas to burn more completely, and thus prevent carbon build-up.

Hmmm, that makes good sense ski, thanks for the info.

[65sohc]

Here is an excerpt from Chevron. The whole page makes good reading. The bottom line is there is no difference in deposits from one octane to another. The only caveat is that this information pertains specifically to California gasoline (because we're so special). However I think it is a fairly safe assumption that deposit control is a universal issue in that it has a direct impact on emissions and all cars must comply with federal standards:

Deposit Control Additive Requirement

A deposit control additive was required in all California gasoline when California Phase 1 RFG became effective in January 1992. The additive must be able to remove ("clean up") existing deposits from port fuel injectors and to keep them essentially free of new deposits. It also must be able to keep intake valves relatively clean. Excessive deposits on these parts increase VOC exhaust emissions. No specific additive is mandated, but each additive must be certified by ARB. Certification requires each gasoline supplier to show its fuel/additive formulation is effective when tested according to procedures specified by ARB.

Chevron gasolines with Techron®, Chevron's proprietary deposit control additive, provide unbeatable deposit control performance.3 While Techron is Chevron's newest and most effective deposit control gasoline additive, its predecessors have provided Chevron gasolines with the level of deposit control performance required for California Phase 2 RFG since 1970.

Here is the link:http://www.chevron.com/products/prod...rfg/char.shtml

[BlackFastAttack]

Thanks alot for your feedback, it does make good sense. Looks like its time to reflash to the performance tune!