Fuel Tips: Narrowing the Fuel Field

David S.
By David S. Wallens
Mar 11, 2020 | Fuel Tips | Posted in Features | From the Dec. 2019 issue | Never miss an article

So many fuels, so many choices. How to narrow down the field? First, let’s assume that we’re talking about a modern, fuel injected car. Right away that discounts all of the leaded products. Zachary Santner, technical specialist with Sunoco Race Fuels, noted that just four products would then cover many popular situations.

Street-Legal: Most race fuels are not approved for street use. In fact, 260 GT is the only Sunoco race fuel to carry 49-state approval. (SS 100 could be called the brand’s California equivalency.) What does 260 GT offer over pump fuel? 100 octane. It’s also a highly refined, fast-burning product, Santner explains. “Some people have noticed that instead of black exhaust tips they see grey or nothing there because it burns so much cleaner,” he adds. Another benefit: longer shelf life than pump fuel.

More Power: A very popular fuel among those seeking max power from modern cars is 260 GT Plus, Santner explains. It’s a 104 octane fuel that contains 13% ethanol. “That little extra ethanol helps with performance,” he explains. “You can tune more on it due to the octane.”

More Acceptance: Santner says that their 260 GTX is popular even though its octane rating is just 98. The reason? No alcohol. “Many racing series don’t want [ethanol] because it masks other chemicals that can be added to enhance power,” he explains. “Many series only test two properties at the track: specific gravity and dielectric constant. Gasoline has a pretty narrow dielectric constant range, but when you add ethanol, the range gets too wide to use the test.” Sunoco 260 GTX is a spec fuel for several series, including Trans Am.

More Alcohol: For those looking for all the ethanol, E85-R has been popular, Santner continues. Where the amount of ethanol in the E85 found at the corner pump can range from 51% to 83%, E85-R always contains 85%.

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View comments on the GRM forums
bentwrench SuperDork
3/11/20 11:44 p.m.

Carbs don't need different fuel than injection.

Fuel injection systems have O2 sensors so they are limited to unleaded blends.

I see no reason to use leaded fuels. I run big motors with lotsa compression on E85 from Thunderbolt.

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