E5 vs E10: Which Fuel is Better for Your Older Engine?

If you've been at a gas station recently, you've likely noticed the different labels on the fuel pumps: E5 and E10. While newer vehicles are designed to handle both, owners of older cars and motorcycles—especially those made before 2011—might need to be more careful. Let's break down the science and how it affects your ride.

What Does the 'E' Mean?

The number following the 'E' represents the percentage of renewable ethanol blended into the gasoline. E5 contains up to 5% ethanol, while E10 can contain up to 10%. While ethanol helps reduce greenhouse gas emissions, it also has different chemical properties than pure gasoline.

The Ethanol Challenge for Older Engines

Ethanol is hygroscopic, meaning it absorbs water from the atmosphere. In older engines with metal fuel tanks and rubber seals not designed for high ethanol concentrations, this can lead to corrosion and the degradation of gaskets over time. Furthermore, E10 has roughly 3.3% less energy than pure gasoline, which can slightly reduce your fuel economy.

"For vehicles made before 1990, E5 is generally the safer choice to prevent long-term fuel system damage."

Performance vs. Price

While E5 (often found in Premium or Super Unleaded) is more expensive per liter, many riders report better mileage and smoother idling. Some motorcycle users have found that the extra cost of E5 is partially offset by a 5-10% increase in range compared to E10.

Track the Difference

The best way to know which fuel is right for your specific vehicle is to test it. Our Fuel Log app allows you to note which fuel type you used at each fill-up. By comparing your consumption charts after a few tanks of each, you can see the real-world impact on your wallet and your engine's efficiency.