How do you answer when a fellow street-machine enthusiast hears a healthy big-block under the hood of the classic musclecar and asks, “So, what kind of gas do you have to use in that beast?

The owner of this 455 Olds engine simply says, “I get the cheapest gas I can at the station.”

Of course, Guy Evens lives in Minnesota where E85 is probably more abundant than in any other state and usually comes out of the least expensive pump at the station. Just to make sure his recently rebuilt Olds, now punched out to 461ci and sporting an aggressive 12.5:1 compression ratio, could stomach the ethanol blend without any problems, he took the engine to R&R Performance in Spring Lake Park, Minnesota, for a comparison test against 110-octane race gas.

“It made more power on E85,” confirms R&R’s Ron Quarnstrom. “To be honest, I thought the engine was beyond the compression ratio; 12.5:1 on cast-iron heads is moving towards the upper limits of 105-octane E85.”

While on 110 race gas the engine pulled 544 horsepower with peak torque of 564 lb-ft. The team switched to an E85-specific carb that provides more fuel at a 9:1 A/F ratio, and the horsepower jumped to 558 with peak torque of 584 lb-ft.

“And it took exactly 29 percent more fuel,” adds Quarnstrom. “Usually with E85 we find it takes 27 to 30 percent more fuel over gas.”

Other than the higher compression and E85 carb, the engine has mild port work on the stock heads and runs an Edelbrock Torker intake manifold.

By the way, you can check out more EngineLabs stories from the R&R SuperFlow dyno, including unusual engines, a 661-horsepower SOHC Ford, a 615-horsepower Mopar Six Pak and a vintage 702ci GMC Twin Six.