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Gary Robinson
Gary Robinson, UK Car Mechanic
Category: UK Car
Satisfied Customers: 735
Experience:  Mechanic and MOT tester for 18 years. Excellent knowledge of cars and the MOT testing scheme.
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What is the difference between EP 90 transmission oil and SAE 90

Customer Question

What is the difference between EP 90 transmission oil and SAE 90
Submitted: 8 years ago.
Category: UK Car
Expert:  Gary Robinson replied 8 years ago.


Thank you for your question.


SAE stands for the Society of Automotive Engineers. The SAE classification system is a way of defining how thin or how thick an oil is. This is known as an oil's viscosity. The classifications are listed here in order of increasing thickness: SAE 75W, SAE 80W, SAE 85W, SAE 90, SAE 140, SAE 250.

What does EP mean?

EP means extreme pressure and refers to the additive used in gear oils. This additive is designed to stop metal-to-metal contact taking place between transmission components. The EP additives are usually based on sulphur and phosphorous. These elements bond to the metal surfaces where there are points of extreme pressure and temperature, forming a sacrificial chemical layer. The sulphur gives gear oils their characteristic smell.


I hope this answers your question.

Regards, Gary.