Oil types (1 article)SyntheticsI posed a question recently about synthetic gear lube for the 5 spd Elite/Eclat transmission and differential. I received varied answers that only added to my initial confusion, but at the same time provided information I was not aware of. For many years I have heard people say good things about "Red Line", a synthetic oil manufacturer. As this is their only business and have a good reputation, I thought I'd stick with them if they had a product I could use. I wrote to Red Line about my question and received the following answer from them. Thanks to all that gave me their valuable input.I have a British 5 speed syncromesh transmission in a 20 year old Lotus car. I have a Salisbury differential that is NOT limited slip. My original literature calls for the following Transmission lube. The differential uses the same type of lube: Shell; Spirax 90EP. Castrol; Hypoy. BP ; EP SAE90. How do these brands/types translate to a Redline product Dave Granquist wrote: A GL-4 lube is a typical API rating for manual transmission lubricant. A GL-5 is a hypoid/EP lube generally used in rear differentials. In your Lotus, if they are recommending the same type lube I would use Red Line 75W90NS in the transmission and 75W90 in the differential. The difference being the friction modifier in the 75W90, designed for limited slip differentials but it works well at reducing the temperature on the gear face and as well fluid temperature, but doesn't work well in most syncro-mesh transmissions. Back to Top | Back to technical index |