Why Fuel Quality Directly Impacts Your Motor Oil and Engine Health

Why Fuel Quality Directly Impacts Your Motor Oil and Engine Health

When people think about motor oil, they rarely consider the role that fuel plays in determining oil performance and longevity. But as Lake Speed Jr., a Certified Lubrication Specialist and member of the Society of Tribologists and Lubrication Engineers, explains, your choice of fuel has a direct impact on your oil and the engine it protects.

Modern engines often rely on oil life monitoring systems to determine when it’s time for an oil change. These systems don’t actually analyze your oil; instead, they use a calculated value known as the oil-to-fuel ratio. The more fuel that ends up in your oil, the faster your oil degrades. Excessive fuel dilution reduces oil viscosity, causing the oil to lose its ability to properly lubricate engine components. It also accelerates thermal breakdown, especially in the presence of unstable fuel components like ethanol.

Fuel can end up in your oil when combustion is incomplete—often due to dirty injectors or carburetors. When fuel isn’t atomized properly, it can drip or spray into the cylinder, where it mixes with oil and bypasses the piston rings, entering the crankcase. This dilution compromises the oil’s protective properties and shortens its effective service life.

To make matters worse, ethanol-blended fuels can lead to internal corrosion and rust, posing long-term risks to your engine’s reliability. That’s why it's essential not only to use high-quality fuel but also to consider fuel system cleaners and lubricants designed to combat ethanol-related issues. 

Your best bet is to use Top Tier Fuels and avoid using E15 or any fuels with higher ethanol concentration. Don't switch between ethanol free and ethanol enriched fuels, as phase separation can occur, causing water to separate from the fuel and cause engine failure or damage.

The use of a complete fuel system treatment that contains PEA, or polyether amine, is also critical to keeping your fuel system clean while protecting it from corrosion.

The takeaway: by selecting the right fuel and additives, you can significantly enhance your oil's performance, extend drain intervals, and protect your engine. Fuel matters—a lot more than most people think.