M41 gearbox oil recommendations?

[SteadyRolling]

Been looking online for some SAE30 / 20W40 oil and to say the options are limited is putting it mildly. What brand would you suggest and would it need to be non-detergent?

[Burdekin]

https://www.mpmoil.co.uk/products/02...ssic-high-zinc

[Rustinmotion]

Originally Posted by SteadyRolling

Been looking online for some SAE30 / 20W40 oil and to say the options are limited is putting it mildly. What brand would you suggest and would it need to be non-detergent?

Talk to Opie oils, very helpful for classic car needs

[ACESRR]

The oil I use in the gearbox of one of my cars is Millers Classic Mini engine oil. It has gear additives and I found it made a significant improvement in the gear change. It is available from Opie Oils previously mentioned.

Andy

[Derek UK]

Make it easy on yourself and use 20/50. You are probably using it in your engine so you just need one type for both. If you want to spend a lot more money on the M41 you could use Redline MTL.
When draining the gearbox, always check that the filler plug can be loosened before you take out the drain plug. Yes, you can fill it from the gearstick hole with 1.8 litres, but you then can't actually check the level via the level plug if you can't get it out! Draining using both the gearbox and OD drain plugs can leave a bit of oil behind.

[SteadyRolling]

Originally Posted by Derek UK

Make it easy on yourself and use 20/50. You are probably using it in your engine so you just need one type for both. If you want to spend a lot more money on the M41 you could use Redline MTL.
When draining the gearbox, always check that the filler plug can be loosened before you take out the drain plug. Yes, you can fill it from the gearstick hole with 1.8 litres, but you then can't actually check the level via the level plug if you can't get it out! Draining using both the gearbox and OD drain plugs can leave a bit of oil behind.

Well, I don't really like straying from the OEM's recommendations but ... I did recently use up a £100 Halford's voucher purely on 20-50, so it would save the hassle (and expense)...

[142 Guy]

20W-50 is probably an acceptable alternative to the recommended 20W-40 and it does not need to be a non detergent oil. If you drive in cold temperatures you will likely notice that the shifting may be slightly more difficult and the synchros may be slower until the gear box has warmed up.

If the synchro cones are getting tired, Red Line MTL is a good choice although significantly more expensive than a jug of 20W-50. If it is available in the UK, GM synchromesh friction modified may be a good alternative to the Red Line and might be a nudge cheaper if you can get it directly from a GM dealer.