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