Reduction Gearbox Oil Notes

[CanyonReveller]

Reduction gearbox oil seems to be an illusive topic on the MG5. Mine wasn't changed at the 4th year service, even after specifically asking for it. Several other posts suggest dealers often don't change it. Allegedly, it should be done after 4years/60k miles.

The reduction gearbox seems to have been a weak spot on other EVs, like the Leaf, and it is very expensive to replace. Tesla have even gone as far as to make a novel system to keep the oil in this box fresh.

I haven't been able to find a comprehensive video or source of information to DIY the job, so I thought I'd drop my findings so far in this forum post. It doesn't look to be too difficult, so I'll do mine at some point over the next 12 months.

The relevant oil is 0.9 litres of Shell SL2808, otherwise known as E6 iX.

The images below are provided from various other posts on the internet, but give an indication of where the filler/drain bolts are and the relevant torque settings for the plugs.

I hope this helps somebody. If you have more info, or a video, please tack it on below.

 

[FCat53]

This looks like a mileage based requirement rather than a time based need. If you have a very high mileage car, suggest you contact Chieveley Mobile, or even James Coates for advice.

 

[vetteman]

Hello from Sweden,
I can´t seem to find the Shell SL2808 oil anywhere, but I found out that Castrol has developed a product together with MG and that it should be working as a good replacement.
The oil is called: ON EV Transmission Fluid W2

Any thoughts about using this? It was easily bought on-line (not cheap) so I´m planning this oilchange in the near future.
Best Regards, Christian Nilsson

 

[Alb]

You can get it HERE and they deliver worldwide.
I wouldn't recommend an equivalent unless you are outside warranty.

 

[CanyonReveller]

You can get it HERE and they deliver worldwide.
I wouldn't recommend an equivalent unless you are outside warranty.

Even outside of warranty, it feels a little risky to go outside of official spec for something so critical.

 

[vetteman]

Thanks for the link!
Here is what Castrol states about their product:

New Castrol ON EV Transmission Fluids for wet e-motors extend driveline life and improve efficiency | Castrol UK & Ireland

www.castrol.com

I do beleive that I will be outside warranty as soon as I do the service myself...our car is a 2021 model, we intend to keep it many years and the horrifying prices they charge for service just makes me mad.
I will most likely use the Castrol product for the reasons above, and cross my fingers that it will work fine

 

[vetteman]

Hi again,
Just an update, I ordered the Castrol product and changed the oil 6:th of December. So far so good, car is running fine, already around 2000km after change. But the oil that was drained (should have been the factory filled oil from what I understand) didn´t look fresh so to say...and the drainplug really needed cleaning because there was a lot of dirt/particles stuck to the magnetic part of it. See pictures.

Out came exactly 1.2 liters, I filled back 1.25. I read 1.3 somewhere though.

 

[CanyonReveller]

That is some very dark old oil! How long did it take roughly? Any idea how many miles that oil has been run for?
I notice your images list ZS EV, is this the oil quantity for the MG ZS?

 

[vetteman]

Yes, very dark!
The car had around 45000km when I changed 2025-12-06. Our car was produced in China in November 2020, and first sold in Sweden in August 2021. We are the second owner. The car had done 23000km in February 2025 when we bought it, now around 48000 (as today 2026-01-07). We use it a bit more, you can say...but that also has "repaired" the not-so-good-looking brake discs.

Yes, there might be a oil volume difference between the ZS compared to the 5. Only explanation I have. But in a workshop manual I downloaded for 10 dollars, it says 0.8 liter +/- 0.05. But when It came out 1.2 liters I didn´t feel comfortable with refilling with only 0.8 liters.

I´m considering changing the oil again only after 6 months or so, just to compare how it looks

 

[CanyonReveller]

Yeah, it's hard to fathom why they want you to take out more than you put in, especially with such a large difference!

I'd be curious to see it after 6 months. It looks like you've hit a textbook change interval on this one but have very dark oil, so a slightly more frequent change might be in order for our car too!

 

[vetteman]

I will update when I do the next change

 

[CanyonReveller]

Did my MG5 today at 51k miles. 0.8l came out, 0.85l went in. Used two standard depth 12 point sockets of sizes 17mm and 5/8 (deep sockets may have access issues). Accessed from underneath only, no wheels off. Really not too difficult once you get going.

Old oil was thick and black. Mag plug was very thick with deposits. New oil is transparent and a noticeably different texture.

 

[Malminor]

Reduction gearbox oil seems to be an illusive topic on the MG5. Mine wasn't changed at the 4th year service, even after specifically asking for it. Several other posts suggest dealers often don't change it. Allegedly, it should be done after 4years/60k miles.

The reduction gearbox seems to have been a weak spot on other EVs, like the Leaf, and it is very expensive to replace. Tesla have even gone as far as to make a novel system to keep the oil in this box fresh.

I haven't been able to find a comprehensive video or source of information to DIY the job, so I thought I'd drop my findings so far in this forum post. It doesn't look to be too difficult, so I'll do mine at some point over the next 12 months.

The relevant oil is 0.9 litres of Shell SL2808, otherwise known as E6 iX.

The images below are provided from various other posts on the internet, but give an indication of where the filler/drain bolts are and the relevant torque settings for the plugs.

I hope this helps somebody. If you have more info, or a video, please tack it on below.


View attachment 40748


View attachment 40749

View attachment 40750

Thank you for the information, I have just completed my oil change

 

[stevemgevcom]

just had mine doe at the 4th service and guess what they charged for the oil £118, its an MG piss take

 

[Malminor]

I paid £38 for a litre of the Shell oil. 0.9 came out so I put the same amount of new in,
about 15 mins as I had the front wheel off to replace the discs and pads.
There was a tiny bit of metal built up on the magnet, which is great for a 100k car.

 

[CanyonReveller]

just had mine doe at the 4th service and guess what they charged for the oil £118, its an MG piss take

At least yours actually did it! Was that the price for the oil alone, or oil with labour? I paid £30 back in October '25, but the same place is now charging about £38 like Malminor says.

 

[stevemgevcom]

yep i know, i was just illustrating the absolute rip off merchants at MG. AND the big problem is who decides what is done in the service as there appears to be no deffinite list of whats suposed to be done. Some MG dealers do it some dont.

 

[CanyonReveller]

My last service was particularly funny as the walk around video with the multi point check after my service said my brake fluid needed replacing. This was a service that explicitly listed the brake fluid change. They remedied the obvious issue, but it does reinforce your point! I'm just trying to maintain the warranty at this point, after that I won't be visiting the dealer unless I have to.

 

[stevemgevcom]

no that was just the oil, the labour for the service (pollen filter £28.34, brake fluid £21.45 & the oil change) was £115, plus ten all te usual over priced unnecessary bits brake cleaner £3.60, windscreen washer £1.50 suppriesd they didnt add fill plug washer

So total was just under £300 for an EV

we are going to tesla land for the next car

 

[stevemgevcom]

My last service was particularly funny as the walk around video with the multi point check after my service said my brake fluid needed replacing. This was a service that explicitly listed the brake fluid change. They remedied the obvious issue, but it does reinforce your point! I'm just trying to maintain the warranty at this point, after that I won't be visiting the dealer unless I have to.

when according to MG the brake fluid change is recommended not compulsory on under 10,000 mile pa but my MG insisted it need doing for warranty purposes, its all just a big conn just wait till i make a claim under warranty they will probably come u with excuse that i was wearing the wrong sort of underwear while driving, axnything to get out of it.