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Buy 75W-85 Gear Oil
75W-85 sits between the two common manual gearbox grades: easier to shift than a 75W-90, more load-bearing than a 75W-80. It is prescribed for a handful of modern manual gearboxes, and there always with an approval number of its own.
Why there is a grade in between
A manual gearbox has to do two things at once: carry the load on the tooth flanks and shift easily. The thinner the oil, the easier the gear change when cold - the thicker, the more reserve under load. 75W-85 is the attempt to balance both, and it is specified by manufacturers whose gearboxes are designed for exactly that window.
In practice that means: swapping this grade for a neighbouring one on your own initiative shifts a property that was deliberately chosen. Stiff shifting when cold is one end of it, wear under load the other.
GL-4 and manufacturer approvals
As with any manual gearbox oil, API GL-4 is the normal case - matched to synchroniser rings made of brass and bronze. GL-5 oils belong in final drives (85W-90, 80W-90) and can attack synchroniser rings over time.
If your maintenance schedule calls for a brand-specific number, it has to be printed on the container. With gear oils that is more common than with engine oil, because the manufacturers test how their own gearboxes shift and not just lubrication performance.
Change and quantity
Car manual gearboxes usually take 1.5 to 2.5 litres, so one to three 1-litre bottles. A change is rarely in the service schedule, but it helps measurably when a gearbox shifts stiffly when cold and the clutch has been ruled out as the cause.
We take back waste oil up to the quantity purchased (waste oil disposal); gear oil is expressly included.
Frequently asked questions
Can I use 75W-90 instead of 75W-85?
Only if the manufacturer permits both. The thicker oil shifts more stiffly when cold - exactly the property the intermediate grade was chosen for. The other way round, a 75W-80 lacks some load-carrying capacity.
Do I need GL-4 or GL-5?
GL-4 for a manual gearbox, GL-5 for a final drive. The viscosity says nothing about that: both categories are offered in 75W and 80W viscosities, and mixing them up costs you the synchroniser rings.
How do I know whether my gearbox needs 75W-85?
From the maintenance schedule, or rather from the approval number stated there. With gear oils the brand-specific number is the reliable figure - the SAE grade alone is not enough to make the choice.
