With such strict laws on modified cars in California, tuners and automotive enthusiasts find all sorts of ways to squeeze every ounce of power out of their vehicles. Whether it is a CARB EO legal intake, a cat-back exhaust, or even changing to high performance spark plugs, these are some legal mods you can install to extract power. Have you ever thought about the fuel you put in your car?

Some people would add in an octane booster of some sort and we all have seen them on the shelves at our local auto parts store. Bottle after bottle, you pour some of that magic liquid that promises to improve the power output of your engine, or so it says on its label. There are even some that look promising with a money-back guarantee. But, have you ever bought one of these horsepower boosters before? Yeah, we didn’t think so.

Matt Farrah from the YouTube series, The Smoking Tire, along with Cobb Tuning, located in Southern California, had recently been working on a Ford Fiesta ST. They conducted an experiment with California’s horrible 91-octane-rated gasoline versus some 100-octane race fuel and yielded some awesome results.

Farrah and the crew at Cobb Tuning got to work on emptying the watered down 91-octane fuel and gave the car ten gallons of 100-octane. By switching the fuel and giving the ECU a more aggressive tune, via the Accessport, there was a very significant increase in horsepower, as well as torque.

Power numbers from stock, to Stage 3 OTS, to Pro-tuned 100-octane.

We’re not talking just a few ponies either. Keep in mind, the Fiesta ST is equipped with a small 1.6-liter turbo inline-4 and this dyno translates to nearly 300-horsepower at the crank. Watch the video to see exactly what was done to transform the Fiesta ST into a real contender and to see Farrah’s driving impressions after the fuel swap and tune.