10 Best Oil Leak Additives 2025 in the UK

STP Engine Stop Leak is designed for those who are dealing with minor oil leaks in their petrol or diesel engines. Its compatibility with both regular and synthetic motor oils makes it a versatile choice for a wide range of vehicles. The product is also safe for oxygen sensors and catalytic converters, meaning it won't cause harm to these crucial components of your car.

One of the main features of this product is its ability to condition engine seals. This is crucial for preventing leaks without the risk of clogging filters or inhibiting oil flow, which can be a concern with some additives. The improved concentrated formula suggests that it aims for stronger performance and efficiency in stopping leaks.

The product is targeted at minor oil leaks and may not be as effective for more severe leaks or underlying mechanical issues that require professional attention. Ease of use is also a positive with this product, as it can be simply added to your engine oil, making it accessible even to those without extensive mechanical knowledge.

STP Engine Stop Leak is a practical choice for car owners seeking an easy solution to minor oil leaks, particularly those who prefer a do-it-yourself approach and need a product that doesn't require complex installation. It’s a highly rated product with a solid track record, as reflected in its positive customer reviews and popularity ranking in the automotive category.

The LIQUI MOLY Oil Additive (200 ml, SKU: 7178) is designed to create a heavy-duty lubricant film on all frictional and sliding metal surfaces in engines, compressors, and pumps. One of its key strengths is its compatibility with a wide range of motor oils, both gasoline and diesel, which makes it versatile for various vehicle types. The product also boasts excellent seal conditioning properties, as it helps reduce friction and allows engine components to run more smoothly.

Its low viscosity ensures that it blends well with existing motor oils without causing any thickening issues. Additionally, the additive concentration is clearly specified, requiring 5% of the motor oil's volume for general use and 2% for motorcycles with wet clutch systems, providing clear guidelines for users. Ease of use is another strong point, as it can be added to motor oil at any time, making it convenient for regular maintenance routines.

In summary, the LIQUI MOLY Oil Additive is a highly rated, compatible, and easy-to-use product, suitable for those looking to reduce friction and improve the smoothness of their engine's operation.

Wynn's Engine Oil Stop Leak is designed to prevent and seal engine oil leaks by rejuvenating worn-out rubber seals, O-rings, and neoprene rings without needing engine disassembly. It restores elasticity and flexibility to drying and shrinking seals, helping prevent future leaks and extending the life of engine components. The product works with all types of engine oils, including mineral and synthetic, and does not change the oil’s thickness or harm the catalytic converter, making it safe for most vehicles.

Additionally, it lubricates seals to reduce wear and cracking caused by heat and oxidation. It is easy to use since it simply mixes into the existing engine oil, avoiding complex procedures or mechanical repairs. While Wynn's Engine Oil Stop Leak provides long-lasting protection, it may not offer immediate results for severe leaks and is primarily intended as a maintenance and minor repair aid rather than a solution for major engine seal failures.

This product is ideal for car owners seeking a preventative solution or a temporary fix for slow oil leaks, especially to avoid costly garage visits. It is less suitable for vehicles requiring urgent, heavy-duty repairs or those with extremely worn seals beyond the product’s restorative capabilities.