BMW Diff - oil replacement/servicing Q

[tomwood]

Hi all,

car is now 4yrs/2500 miles (2013 build) and I'd like to service the diff whilst doing other bits on the car. I've had a look in the archive but the message is confused as to how much oil should actually be in it. Questions I'd really like answers to from those that know:

1) should I be refilling to the filler hole on the BMW Diff or is that going to over fill it? I'd be happy to empty it and refill with a set amount of oil - how much to put back in would be the question?

2) what is the correct oil to refill with? When I built the car caterham supplied a diff oil + friction modifier. I understand that caterham now stock a Motul 75-140 based oil that requires no friction modifier apparently. Do I have this right and is this the one to use in the BMW diff that has an LSD in it?

Thanks

Tom

[ScottR400D]

I changed mine at about 3000 miles. Sucked the old oil out with a Pela, and refilled to the fill hole with Redline 75-90 GL5 from Opie oils. 

It was originally filled to the same point and has not been a problem. From memory it's about 1.2 litres. Now at 4000 miles with 4 track days included. 

Peter

[ScottR400D]

I changed mine at about 3000 miles. Sucked the old oil out with a Pela, and refilled to the fill hole with Redline 75-90 GL5 from Opie oils. 

It was originally filled to the same point and has not been a problem. From memory it's about 1.2 litres. Now at 4000 miles with 4 track days included. 

Peter

[tomwood]

Thanks Peter - did you add friction modifier to the redline oil?

[ScottR400D]

Hi Tom. No I didn't. 

I built my car mid 15 and used the Comma oils supplied/recommended by CC. Since then I've changed the box to Redline MTL, the engine to Millers 10/40 and the diff as mentioned. 

Those were all recommended by Opie and no friction modifier was suggested. Below is the question I asked and the answer from Opie. 

 

On 24 Aug 2016, at 08:37, Opie Oils <sales@opieoils.co.uk> wrote:
 

Hi Peter
This is ideal.
http://www.opieoils.co.uk/p-1016-red-line-synthetic-gear-oil-75w-90-gl5.aspx
Regards

Tim

Hi Tim.
I bought Redline MTL from you for the gearbox of my 2015 Caterham R400 a while back. A definite, if small, improvement in ease of change, I think.
Is there a Redline product recommended for the differential? It's a BMW diff, I understand, with LSD.
Kind regards
Peter Scott

 

[tomwood]

Good stuff, thanks.

I too have MTL in the gearbox and rate it.

I've just finished emptying the diff with the Pela (it was full right up to the filler hole still) and indeed a rough measurement suggests about 1.2L has come out. It's done 2500 miles like that without any leaking and has performed well so filling to the hole would appear to be fine as you surmise.

initially the oil did look very clean and wondered if I was wasting my time but to be fair there was a fair bit of crud in the bottom 100ml or so that came out.

ive found the old diff oil bottle from when I filled it originally. It's a caterham branded bottle of comma oil which simply lists GL5 on it. I added friction modifier to that when I put it in which is why I was asking the question but I've looked up the redline diff oil you've listed and indeed that already contains the required friction modifier.

i'll go with your suggestion and get some ordered.

thanks for your help,

Tom