Morris Minor Owners Club

Hi again, I know this has probably been mentioned a thousand times but,,,,,,
What is the best oil for,,,
1 rear diff,
2 gearbox,
3 dampers, and any others, I have plenty of 20/50 for engine but now want to do all the others, many thanks in advance to all you talented moggers out there ,

I’ve used Castrol EP 90 in the axle without problems. If you have a standard Morris gearbox the usual 20/50 will be fine.

Oh, and a well respected former member of this forum recommended SAE 40 or 50 for the dampers. He said to drain the old stuff,flush and replace with new. He was generally right!

As regards the EP 90 - use only GL4. GL5 will destroy the bearings.

In 40 years of ownership I have always used 20/50 in the engine and gearbox. The cheapest I can find and change the engine oil frequently. I am running the original 1969 engine with one rebuild in the 1990's.

yes, I always buy the cheapest 20w50 I can find. B & Q were doing one for £11 at one time so I purchased a 'few'.

philthehill wrote: ↑Fri Oct 18, 2019 12:18 pm As regards the EP 90 - use only GL4. GL5 will destroy the bearings.

Glad you mentioned that. I didn't know there was more than 1 sort of EP90. So I looked it up and found this description of the difference.
https://www.ryeoil.co.uk/shop/ep90-gear-oil-gl4/

Let me start by telling you that Gear Oil’s are not Transmission Oils. Transmissions have gears and synchronisers. These of which require a different additive package. If you are wondering if GL5 covers GL4 the answer isnt simple. GL5 covers GL4 in terms of protection, but contains to much detergent and will strip any white metals and strip any brass synchronisers.

Simply, GL4 gear oils are intended for axles with spiral bevel and hypoid gears operating under moderate to severe conditions of speeds and loads. GL-4 gear oils also have a low detergent level, which help protect yellow and phosphorous metal elements of the gear box. You can use GL-5 for high-speed loads and also for low-speed torque systems without yellow metals.

philthehill wrote: ↑Fri Oct 18, 2019 12:18 pm As regards the EP 90 - use only GL4. GL5 will destroy the bearings.

Sorry, should have mentioned that...

I find Millers a good oil 20/50

I realy can't see in this day and age why you would use engine oil in a gearbox, its not engineered for the job, 50 years ago it was the only multigrade avalable but oil has moved on massively in that time, Iv'e been using a modern 75 w 90 gl4 in ours which seems to work very well, nice slick shift, no horrible noises yet!
In the dampers i believe motorcycle fork oil is widely used.

There is absolutely no need to use a 75w/90gl4 oil in a Minor gearbox.

https://www.halfords.com/motoring/engin ... -90-gl4-1l

The Minor gearbox is not sophisticated enough to require 75w/90gl4 and it is the wrong oil for the Minor gearbox.
Even the use of 75w/90gl4 in modern gearboxes and rear axles should only be considered where it is specified by the vehicle manufacture.

Whilst 75w90 gl4 will work - 20w/50 engine oil is more than adequate for the Minor gearbox. Whilst the oils have moved on the Minor gearbox has not so does not require a upgrade in oils.

The synchro rings of the Minor gearbox need to be cleared of oil quickly when changing gear so as to synchronise the gears and alleviate crunching of the gears when meshing. 20w 50 is ideal in this function.

Again there is no need to use any other oil than Armstrong damper fluid or similar ARhttps://www.moss-europe.co.uk/tools-equipment/l ... a149m.html if you want to keep the dampers fully standard or if that is not available a SAE 20/20W mineral oil should be used. To stiffen the dampers if required a straight SAE30 or SAE40 mineral oil can be used.
The majority of MC fork oils are 15W though 20W can be obtained. https://www.carparts4less.co.uk/search/ ... gJ3c_D_BwE

Hi,
This is an interesting read and I will now go and check that my diff oil is GL4, I have used it in previous Minors diffs without issue but no harm in checking.
I was reading through the manuals section on lubricants the other day and that recommends SAE20/20W for the dampers, so this is what I ended up buying:

https://www.ebay.co.uk/itm/Silkolene-SF ... 2749.l2649

As you say, 20W for a reasonable price can take some tracking down these days.
Best wishes,
Mike.