With a little extra time on my hands due to the current crisis, I decided to change the differential oil in my 2016 SL 400. It's a relatively straightforward procedure. The drain and fill plugs are 14 mm hex. You can get a ratchet on the fill plug at the top of the differential, which you should loosen first. The 14 mm drain plug is also a hex, but due to the exhaust being fairly close I couldn't use the ratchet to loosen it, using a large adjustable wrench instead. With 25000 miles on my car, the oil was a little bit dirty and there were some minor metal shavings on the drain plug. You could probably go to 50,000 mile intervals if you wanted to.

I drained about 1 quart out of the differential. Mercedes recommends 85W-90 gear oil which I couldn't get locally. I used Lucas 75W-90 synthetic gear oil instead. You will also need to use some sort of a pump to get the oil up to the fill hole.

Sorry, no pics, but this is relatively easy. I put the car on ramps out the back of the garage so that it was relatively level during the procedure. The whole drain & refill took about 30 minutes.

 

Is this service one that MB recommends as a component of normal maintenance? Has anyone had this done by a dealer and at what cost? Just curious as I have a friend with a lift and may do it myself but only 23K miles so I will wait a while. Thanks for posting and letting us know it is a relatively easy job and can be performed with simple hand tools and a manual pump.

 

I believe this is a recommended service on some AMG models. It's probably not a recommended service from Mercedes on non-AMG models, but the fact that there are drain and fill holes should tell you something (not all differentials have them). I change the differential oil on most of my cars. The one where it definitely needs to be done is an American made SUV that I have at 25k miles. The gear oil pump you should be able to get at most auto parts stores. The 14 mm hex socket I have as either my wife's Audi and/or a previous BMW I had used the same drain/refill socket. Some auto parts stores will have it or can you get it on the web.

 

I changed the diff gear oil in my C7 Corvette last year. Used a $8 pump I bought at Harbor Freight. EZ PZ.

 

Beyond the recognized maintenance of the car, I do an entire flush of fluids at five years from the born on date. While a great deal of these fluids show to be 'lifetime' in today's cars, with the additives and synthetic composition, I just do not trust that vehicle fluids will remain in a constant state much longer than five years given the heat cycles that they experience. I may be ****, (don't ask the wife!), but fluids are cheaper than components. That's just my several dollars worth of input.

 

Is 1 quart adequate to fill the differential?

 

you’ll probably need 2 quarts

 

Roger that, thanks.

 

You can get 2 quarts to be on the safe side. Once you drain the differential, and start to refill, once the oil starts to run out of the fill hole you are done. You don't want to go beyond that.

 

I may be overthinking this but trying to understand what gear oil to buy. I have read that Mercedes recently changed from 85W90 to 75W90 as the recommended gear oil. I am having a hard time finding out which oils have the correct MB spec. Prices are all over the place from less than $9/ liter to as much as $25/liter. Since only buying 2 bottles it's not a big deal as I am more concerned with buying the correct and best oil.

LiquiMoly, Motul, Mobil 1, Red Line? What do you folks recommend? What is the latest MB spec number? Anyone know who makes the Mercedes branded oil? I may call my local dealer and ask what they use. Thanks.

Just called my dealer and they use 75W85 synthetic Mercedes branded. Sells for $58/bottle. No thanks.

 

Mercedes uses rebranded Castrol Syntrax

Castrol 80W-90

They make a 75W-90 also which should be easier to get. (probably why Mercedes now also approves 75W-90)


For a while during COVID, I had a hard time getting consistent supply of Castrol Syntrax 80W-90 in the USA. I used Mobil1 as an alternative. It works fine.

 

Thanks. I'll check out Mobil 1. FCP Euro recommended Liqui Moly 85W90.

 

I think the key thing is the 90 weight rating. The cold temp part 75W, 80W, 85W probably isn’t as much of a factor unless your car sits outside in cold temps.
And even then, it’s proably splitting hairs. Liqui Moly will also be fine.👍

Limited Slip Diffs with clutch packs are a different animal so, that may be more critical.

 

75W85? Can you double check that?

ECSTUNING says this fits our cars.

2015 Mercedes Benz SL400 Base Convertible 231.465 V6 3.0L Search SiteSearch differential fluid - 20012 - Manual Transmission / Differential Fluid 75w90 - 1 Liter (ecstuning.com)

 

The latest spec 235.0 for (standard) passenger car diffs from Mercedes (as 3/08/22) approves SAE 75W-90, 80W-90, 85W-90, 90 hypoid gear oil
You can find the Specs here:
https://operatingfluids.mercedes-ben...sheet/235.0/en

All the operating fluids can be found here.
https://operatingfluids.mercedes-benz.com

 

I went with the Castrol.

Castrol - Syntrax Long Life 75W-90 Differential Fluid

CASTROL GEAR OIL 75W90 SYNTRAX LONGLIFE - 558.32.24 - CASTROLCASTROL GEAR OIL 75W90 SYNTRAX LONGLIFE - 558.32.24 - CASTROL - Content: 1,0 l - https://www.amazon.com/dp/B00C3JV2GC/ref=cm_sw_r_apan_i_HB8RMNWZT8A89H12C457?_encoding= UTF8&psc=1

 

You should be good 👍
As long as it shows up. I’ve had some availability/delivery issues from amazon lately 😟

 

Amazon built a huge warehouse, over 1 million sq ft and a separate sorting facility in Hagerstown. Almost all deliveries are now next day and by Amazon employees driving Amazon vans.

 

The Castrol - Syntrax Long Life 75W-90 Differential Fluid isn't listed in the 235.0 spec list of oils, whereas the Liqui Moly is. The Castrol 80W-90 is listed, but not the 75W-90.

 

I realize the site may be difficult to follow, but update 235.8 shows the approved 75W-90 Castrol for passenger cars.
https://operatingfluids.mercedes-ben...sheet/235.8/en

 

Thanks! I was looking only at 235.0.

 

I think you will get lots of opinions regarding what brand oil to use. All the brands you mention are good quality. For me, how often you change the oil is more important than any particular brand. I would use a full synthetic differential fluid and as long as you are changing it every 25k miles or so, you will be all set.

 

Fixed my typo. It's 75W85 that my dealer said they use.

 

Of course! RedLine is the only brand that I can find at that weight. However, Mobil Delvac 1 is listed in the 235.8 spec and it is available on Amazon.

 

^^^^^ This 👍 ^^^^^^
Understandably the Mercedes documents can appear abstract looking at them for the first time. It's important to understand many of the oil's listed by Mercedes are discontinued because those documents, while updated and revised, are still old. 235.7 is from 2012 or so. 235.8 I believe is 2018 or so. Look to them more as addendums.
What you want to focus on is the revised 231.1 Which approves weights 75W-90, 80W-90, 85W-90, 90 for standard diffs. The 90 weight part of that, being the most critical (and constant) part of that spec. for an open rear diff.
Many lubricant/oil manufacturers improve (and rename) their products constantly. As an example, Castrol has discontinued many of the oil's listed in the MB 235 series spec sheets. Also most are/were EU products only, not readily available in the US. Castrol Syntrax Universal 80W-90 has been discontinued as well as Castrol Syntrax Plus 75W-90 (EU product). Before that Castrol was branded as plain Castrol Syntrax ( a different spec oil) and was discontinued in 2010 or so...

https://www.broughtonlubricants.co.u...iversal-80w-90

https://www.opieoils.co.uk/p-210726-...arbox-oil.aspx

As another example, the Liqui Moly product you referenced from ECS is LIQUI MOLY HIGH PERFORMANCE 75W-90. It is technically a different version than the "blessed" German version LIQUI MOLY Hypoid-Getriebeöl which is an 85W-90 listed in 235.0. I'm betting the 75W-90 version is improved.

I had a discussion with Castrol at some point about this. They pointed out that the current Castrol Syntrax Long Life 75W-90 Differential Fluid is almost identical in specification but has a much higher flash point than previous versions, and according to them is a superior product. For whatever that's worth.

In the end, the HAG215 is available in many cars and is quite robust. Chrysler also uses it (and specs different brand oils) Chances are the open version of this diff will outlast your car. It's not a complicated mechanism. The limited slip version is a different matter. Also remember these gear oils are formulated to work in manual transmissions where a cold gearbox leads to synchro, dog teeth and other shift related complaint issues. Hence the lighter cold temp ratings being more important.

Yup. 1 GAL, That is handy if you have to do multiple cars. That is also a EU spec oil. Just be aware that just because it's "listed" on Amazon doesn't mean it's actually available. I ran into this issue sourcing the EU spec. Castrol Syntrax as stated above. It is still listed on many site's, but it doesn't actually mean its available. Or it may only available in 208 litre drums

I wouldn't over think this too much, use what you're comfortable with and focus more on interval replacement as mentioned by rnmaas.