One Oil Fits All - 75w90 in R380

There's a few gear/transmission oils now that meet GL-4 & GL-5. This means they have the correct EP additives for diffs and the transfer box but won't cause any issues with brass in the gearbox.

I'm trying to minimise the amount of oils I have in my stash. I'm hoping that I can use the same engine & gear oils between the Defender and my Mothers Suzuki Jimmny. Even better, if I can use the same oils in the gearbox, transfer box and diffs in both vehicles.

I'm going to try and use a 75w90 in the R380. I was wondering if anyone had any experience using a 75w90 oil in the R380?

Personally I've only ever used the correct spec for whatever application I need it for, having two types of oil seems easier than having a spare gearbox

I remember a mate once saying an oil is an oil and used the same stuff for everything. He was forever changing engines, gearboxes etc

I'd say use the right type for each part, otherwise report back and let us know what happens!!

All im gunna say is there is a reason LR and the like give a list of correct oils to use...

The R380 is designed for ATF - later changed to MTF94 ( by LR ) - and has a pump to ensure proper lubrication, and on the ROW spec vehicles, said pump also pushes the oil through a cooler. ( IME, some prefer ATF, some prefer MTF94 - probably a tolerance thing)

I'd suggest you use the oil specified by the designer of the box.

Agreed. I do prefer proper EP90 in my tranny and diffs tho, instead of the usual 80w/90

bankz5152 said:

Agreed. I do prefer proper EP90 in my tranny and diffs tho, instead of the usual 80w/90

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Aye, Tis fine, as they are both gear oils with the right qualities and additive packs - and perhaps most importantly to the OP's question are not pumped. Our diffs (etc ) are due a change soon, and I'm gonna try some fully synthetic gear oil - but still gear oil - prolly makes posh or summat .....

SWMBO's R380 really does like MTF94 - it was a bit whiney before I changed it to fresh ATF - and then the synchro's didn't feel right to me ( too slow ), so I changed it to MTF94 and it's sooo much nicer now

My old 90 did not like fully synth oil, made it leak! (well more than a landy does!) changed back to semi on the next 6k service, hey presto no leaks... strange eh?

Reckon you could happily use semi synth in an engine that asks for fully synth even if changed yearly/6k? Only ask as the Mrs Hyundai uses 5w/30 fully synth but me 110 uses semi...

The R380 in my Defender seems to prefer MTF94 over ATF.

MTF94 being a 75w80 GL-4 oil therefore the 75w90 I want to use will only be slightly thicker at operating temperature.

Also the 75w90 GL-4 I want to use is fully synthetic where as the MTF94 I use is a mineral oil so the 75w90 will have better cold start characteristics.

I was more curious about shift quality. Assuming the box shifts nicely I will get an oil analysis done after 6 months to ensure there isn't excessive wear materials in the oil.

bankz5152 said:

My old 90 did not like fully synth oil, made it leak! (well more than a landy does!) changed back to semi on the next 6k service, hey presto no leaks... strange eh?

Reckon you could happily use semi synth in an engine that asks for fully synth even if changed yearly/6k? Only ask as the Mrs Hyundai uses 5w/30 fully synth but me 110 uses semi...

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This is usually because the synthetic oil cleans sludge that's built up around seals over years of use.

I'm currently running my 300TDi on a diet of heavy duty diesel engine oil and short oil change intervals to help clean up 21 years/76k of deposits and Forte seal conditioner to help soften and slightly swell the old seals. It has stopped a leaky rear crank seal in it's tracks! Hoping to move over to Shell Helix Ultra 5w40 later this year, the same engine oil I plan to run in the Suzuki Jimmny.

bankz5152 said:

My old 90 did not like fully synth oil, made it leak! (well more than a landy does!) changed back to semi on the next 6k service, hey presto no leaks... strange eh?

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Seems a common problem! The precise qualities of synthetic oil which make it a better lubricant are the things which make it leak out of some engines not originally designed or made to the tolerances required. Good vid on u tube by "Engineering Explained" about the differences - worth a look ...

bankz5152 said:

Reckon you could happily use semi synth in an engine that asks for fully synth even if changed yearly/6k? Only ask as the Mrs Hyundai uses 5w/30 fully synth but me 110 uses semi...

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Which sort of answers your question - whilst you're unlikely to blow the hyundai up, for the extra cost I would advise against it. I wonder if you can actually get semi synth with the right ACEA spec anyway ? Oil changing is the cheapest maintenance anyone will ever do

Thought as much! Mainly to save space in the garage! The saving would be nice as I could buy 10L+ at a time and do both cars rather than two different yet similar oils... Though the mrs would never forgive me if i fckud her beloved hyundai

Bailes1992 said:

The R380 in my Defender seems to prefer MTF94 over ATF.

MTF94 being a 75w80 GL-4 oil therefore the 75w90 I want to use will only be slightly thicker at operating temperature.

Also the 75w90 GL-4 I want to use is fully synthetic where as the MTF94 I use is a mineral oil so the 75w90 will have better cold start characteristics.

I was more curious about shift quality. Assuming the box shifts nicely I will get an oil analysis done after 6 months to ensure there isn't excessive wear materials in the oil.

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I'd try fully synthetic MTF94 first, before adding 10 points, which I think will cause issues with your synchro and probably the pump too - do you have a cooler ?

It's clearly your call to change to 75w90 - and if you can justify repeat oil analysis, you might be doing valuable research - I think you'd need to do said research in a fairly controlled way though for it to be valuable. I'm not trying to teach you to suck eggs here, but the R380 ( and its predecessor ) were designed by LR and use the same basic layout - and originally the same oil, so it clearly worked, and continues to do so - I'm advising some caution, possibly unwarranted.

I'd be interested to know how you get on - have you thought of talking to Ashcroft transmissions ? I see they are still recommending ATF for the LT77, and MTF94 or ATF for the '380.

I seem to remember that you want to avoid GL5 if you have bronze in your gearbox. Older technology needs older spec oils