Differential oil question - what is "hypoid" oil?

[minime1275]

The owners handbook that came with my 325 auto says you should use an SAE 90 hypoid oil for the rear differential (the exact specification of which is available at my local BMW dealer).

Ive just bought some Castrol Differential Oil (80-90W), but nowhere on the bottle does it mention the word "hypoid". What does hypoid mean, and will the Castrol be suitable for my 110k mile 325 auto?

[Templ8e30]

As far as I know Hypoid is type of gear arrangement where the gear teeth slide past each other as they turn. E30 differentials have this type of gear.

Because of this kind of friction a special type of gear oil is needed hence' hypoid' gear oil.

I'd get the right kind of oil and don't bother with multigrade gear oils like 80/90w, get the correct 80w for a gearbox or 90w for the diff.

The thinner 80w or 80/90w can transmit more gear noise than a 90w and isn't as good as a straight weight oil.

90w hypoid is available from the majority of motor stores for about Ԛ£5 per litre for a known brand.

Cheers,

Iain T

[minime1275]

Thanks

[Brianmoooore]

Isn't GL5 the equivalent of hypoid these days?

[Jhonno]

Ԛ£15 a litre from your dealer for diff oil..

[calder]

try Oilman - Opie Oils. About Ԛ£8 a litre for some nice Silkolene gear oil