10 Best Engine Additives 2025 in the United States

The Lucas Oil 10002 Heavy Duty Oil Stabilizer is designed to enhance the performance and longevity of your engine oil. This pack of four 1-gallon bottles is compatible with multiple vehicle types, making it versatile for different users. One of the standout features is its ability to increase oil life by at least 50%, which could be a significant benefit for users looking to extend the intervals between oil changes.

It also claims to reduce oil consumption, eliminate dry starts, raise oil pressure, and increase power and fuel efficiency, which are valuable enhancements for maintaining engine health and performance. Lucas Oil, the manufacturer, is a well-known brand in the automotive industry with a strong reputation.

However, the product is quite heavy at 31.4 pounds, which might be a drawback for some users in terms of handling and storage. Additionally, while the performance claims are promising, actual results may vary based on individual engine conditions and usage patterns. This product appears to be a solid choice for those looking to improve their engine's performance and longevity, especially for users who have experience with oil additives and are aware of their proper application.

The Red Line 60103 SI-1 Complete Fuel System Cleaner is a concentrated liquid additive designed to clean fuel injectors, carburetors, valves, and combustion chambers, helping to improve fuel efficiency and reduce buildup of deposits. It stands out for its strong cleaning action that works in one treatment per tank, making it easy to use. The product is unscented and comes in a 15-ounce bottle, sold as a two-pack, which offers good value if you use it regularly.

It’s compatible with most gasoline engines, and the brand Red Line has a solid reputation in automotive additives, supported by a high customer rating of 4.7 out of 5 stars from thousands of users, suggesting it is effective and trusted. Some users might find the price a bit higher compared to simpler fuel additives, but the concentration and performance justify the cost. Additionally, it is mainly for gasoline engines and not suitable for diesel vehicles.

For those seeking a reliable, powerful cleaner that also helps prevent corrosion and fuel system wear, this product is an excellent choice, especially for anyone wanting a one-step treatment to boost engine performance and fuel stability.

The Gumout 510023 Regane High Mileage Fuel System Cleaner is designed as a universal fit additive, compatible with most gasoline engines without manufacturer restrictions. It features an advanced cleaning formula called CarbonClear technology, which combines three detergents—including PEA and PIBA—to clean fuel systems more effectively than older single-detergent products. This helps remove carbon build-up and can improve engine performance and fuel economy after just one use. The product also reduces friction in the engine’s upper cylinders, benefiting vehicles with higher mileage that may experience more wear and tear. Additionally, it combats ethanol and water corrosion, providing engine protection over time. The dosage is simple, as it comes in 6-ounce bottles meant for use per fuel fill-up, making it easy to apply without guesswork.

Gumout is a well-known brand in automotive additives, and this cleaner holds strong customer ratings with 4.6 out of 5 stars from over 5,600 reviews, reflecting high user satisfaction. While it is well-suited for high mileage engines, those seeking specialized additives for diesel engines or very specific fuel system issues may need a different product. Also, the six-bottle pack can be somewhat bulky, which might be more than occasional users require. This cleaner is a reliable and easy-to-use option for drivers aiming to maintain engine health and improve fuel efficiency, especially in older vehicles.