Gas Or Diesel? This Engine Can Run On Both At The Same Time

As fuel prices surge in 2026, electric vehicle owners may be feeling a bit smug. The remainder of us are currently paying an average of $4.30 per gallon for gas, or $5.49 for diesel. Some lucky states are paying a bit less, while Californians are paying more than $6 per gallon. It's a hit on our budgets and wallets, and there's no relief in sight.

Making the switch to an electric vehicle is a substantial adjustment, and many drivers may not feel ready. They may be concerned that the infrastructure doesn't fully support the technology and worry about the availability of chargers. While there are few alternatives, researchers at the University of Wisconsin-Madison are at work on a novel concept: an engine that uses both gasoline and diesel.

Called the Reactivity Controlled Compression Ignition (RCCI) engine, this concept is just that — a theory that exists only in the lab, at least for now. Combining the fuels means this engine achieves a fuel-to-power conversion rate of up to 60%. Typical gasoline engines convert 30-40% of their fuel into power, while the average diesel engine converts about 45-50%, meaning the RCCI engine is a much more fuel-efficient idea. Here's how it works.

We all know not to put diesel into a gasoline car, but you may not understand why. While they are both refined from crude oil, gasoline is more refined and thinner, so it burns faster and is a good choice for higher horsepower engines. Diesel is thicker and burns more slowly; it's used for larger machines that need more torque.

The conceptual RCCI engine works like a standard gasoline engine at first, mixing air and fuel in the combustion chamber. Then, at a particular point in the process, diesel fuel is added to the chamber for a mix of gas, diesel, and air. As the piston moves, a bit more diesel is injected just before ignition, and the mixture of gas and diesel then ignites and causes the remaining gas to ignite. The result is not only more efficient fuel, but it's also cleaner, putting out lower emissions. It's an interesting concept but of course it would mean you'd have to visit two different fuel pumps to fill up!

Continuing to burn fossil fuels at the current rate is widely considered unsustainable, and scientists, engineers and more continue to attack the problem from all angles. Potential alternatives to electricity and fossil fuels include hydrogen fuel cell technology; biodiesels, or renewable fuels manufactured from alternatives such as vegetable oils; synthetic fuels; natural gas; and renewable diesel.