gearbox oil

[horrace]

so far from previous threads i have leanrt that in my gearbox i need 10-40 if its in good shape or 20-50 if in not so good shape, its just been rebiult so im assuming its in good shape! as long as i use a decent quality engine oil does it matter if its mineral or semi synthetic?

[bmcecosse]

Just use mineral 10W40. All this 'semi-synthetic' nonsense is only for modern cars with very close tolerances. For your engine - ASDA 20W50 is fine.

[horrace]

i have some of the 'classic' comma engine oil in 20w50 this would be ok also then? in previous threads it was stating that 10w40 gives better economy? which was why i was going to go for it but you reckon not?

[cadetchris]

10w40 is good as is 20w50. it depends what you have to hand really.

[horrace]

i have spare 20w 50 but dont want to chuck it in just cos i have it i would rather put in whats best for the box

[cadetchris]

well in that case, follow the advice of the moggy Oracle and use 10w40. if its good enough for him then its good for your gearbox

[bmcecosse]

Yes 10W40 if it's a good box - that will cause less drag and better economy. But 20W50 for the engine!

[ampwhu]

so you'd put semi synthetic in a 50 year old gearbox?

i use that in my new car. in the 803 i use 20/50 in the engine and box. never had a problem in years