Jasonoff

Has anyone else been told this by their respective dealership?

I will ask them for the bulletin as evidence but from what I can tell 325.5 (BQ 1 03 0005) pink colour is for their truck fleet and I can't find much on it being a suitable replacement for 325.0 (BQ 1 03 0004).

Apparently it's mixable and will be used going forward.

EDIT: TLDR yes, you can mix them see https://mbworld.org/forums/c63-amg-w...ml#post8862946

Valvestud

The link below shows the approved spec numbers by engine. It shows the M156 is to use 325.6, which is pink. So, I'd also like to see the bulletin.

Mercedes-Benz Operating Fluids

Regards,
Joe

Jasonoff

Same, saw tones about 325.6 which is in all the facelift models but nada on 325.5 so I'm skeptical.

EDIT: On most of the official MB online parts sites it will show the below as well.

HLG600

Where are you seeing that 325.5 was exclusively for MB trucks?

To my understanding, 325.5 replaced 325.0 a few years ago. When the head bolt job was done on my car 3+ years ago, the shop switched to the new spec (from the greenish-blue coolant that was in the car at the time to the pink coolant).

https://blog.fcpeuro.com/engine-cool...-your-mercedes

Seems like just a subtle revision from .5 to the .6 variants.

Adi-Benz

I just redid mine with blue OEM 325.0. also got a new bottle from dealer, it's replaced with a blue different non Mercedes brand

Jasonoff

I didn't say exclusively. It does however only show up on the truck side for operating fluids.

Trucks --> https://bevo.mercedes-benz-trucks.co...ory/coolant/en
Cars --> https://operatingfluids.mercedes-ben...tegory/coolant

Jasonoff

This is a decent explanation on the differences between G48 (Blue 325.0) and G40 (Pink 325.5 and .6 I guess?)

https://min.news/en/news/451bca71fe3...e171e8bc0.html

Jasonoff

I found more here in section 4 --> https://operatingfluids.mercedes-ben...sheet/310.1/en

So you can put 325.6 (pink) in older engines that were spec'ed for 325.0 (blue).
If the below is accurate on the difference between 235.5 and 325.6 then it "should" be fine.

Diabolis

Whatever you do, do NOT mix a HOAT (blue) with a Si-OAT (pink) coolants without completely and thoroughly flushing the system first. When you combine the blue and pink coolants, they turn into a gel, and Jell-o does not flow. There have been a number of reports of blown engines because the system wasn't properly drained of the blue stuff before someone topped it off with the pink coolant, resulting in a catastrophic failure.

The newer pink Si-OAT formulation is approved for use in all MB cars made in the last 15 or so years as it does not negatively interact with any materials in any part of the cooling system, it has the same seal conditioning, anti-bacterial and anti-oxidation properties as the blue HOAT stuff and IIRC is even better at preventing cavitation (air bubbles) at the water pump impeller, but it does require a complete system flush before it can be used. Some of the older production engines (like the early diesel OM642s) require a replacement of some seals around the water pump before the pink coolant can be used which would otherwise degrade and fail, but not the M156. The pink stuff is a newer formulation that can be used in place of the old one - they just can't be mixed.

Jasonoff

I didn't think they could be mixed but I was very specifically instructed that MB said this was ok.

I also wonder why official documentation I posted above say they're compatible? I'm still skeptical.

Diabolis

They are compatible - as in the pink one is not going to destroy anything in a car that was designed to run on the blue one - but you can't mix them due to different chemistry.

Jasonoff

What's the catalyst for gelling? I have mixed the 2 (100ml of 50:50 mixed G48 and 100ml of 50:50 mixed G40) for shěts and giggles to see what happens.

I will be replacing my overflow tank and hoses along with doing a full flush so I'm not concerned with switching to the G40 pink stuff.

Diabolis

I don't know - you'd need to talk to a chemistry major for that. Perhaps those specific ones might not gel for a while, but they will start to react with each other and end up eating various seals in as little as 24 hours... which also happens when you mix the two.

Jasonoff

Oh, you're not a chemistry major? My bad...

Adi-Benz

Well I have a biochemistry major, and at the time when I looked at the compositions, it seemed to me that you would be able to mix them (contradicting the don't mix colors rule) which surprised me. Of course, I wouldn't say anything of that nature for fear of getting bashed on the forums but also I can't be bothered to look into it enough. Pour both in a cup and let's find out?

But also as I mentioned I could get blue from the dealer so why not just get that?

Jasonoff

See https://mbworld.org/forums/c63-amg-w...ml#post8862185 lol

Still a liquid this morning.

Diabolis

If you think I am pulling things out of my ***, all you have to do is google "coolant mix gelling". I know a thing or two about oils (but not coolants), and I used to do some statistical failure analyses for MB so I am reporting on what I saw in their data. It is a free country and it's your car though... you can run whatever you want and mix whatever you want.

Jasonoff

You appear to be argumentative with me where I am just reporting here what I have been told. Incase you misread, I didn't say you can mix them, the dealership said you can.

I will ask for a copy of the service bulletin so I can post it here. If it explicitly says you CAN mix the two, are you going to argue with "me" more?

Diabolis

If I misinterpreted your "Oh, you're not a chemistry major? My bad..." comment, I apologize - but that definitely comes across as a snipe. And, where am I arguing with you exactly? I never took issue with anything you wrote.

Jasonoff

Possibly some 2 way misinterpretation. No biggie.

I'm waiting on the bulletin and will post it up here when I have it. I did confirm again with the service manager this time. MB gave them the green light to mix the 2. No requirement to flush if one with G48 comes in and it needs to be topped up.

Jasonoff

Well this drives a nail in that coffin.

HLG600

I would still do a quick flush of just distilled water in between draining the blue and final-filling with pink.

Regardless of the factory-OK, something about an "increased mauve proportion" in my engine isn't sitting right with me.

Jasonoff

I always do a flush even if it's the same coolant. Given the above, I will likely just do a single flush and not worry if there's any minor residual left over.

Diabolis

This is from the Glysantin site - Glysantin makes both the G48 and the G40 coolants for MB:

"GLYSANTIN® products can be mixed chemically, but we do not recommend this. Each product contains a different combination of additives that are compatible with the different materials in the cooling system. Mixing different additives can impair their overall performance and reduce the level of corrosion protection."

So, this may be what MB is relying on. Their cooling systems are generally well designed and they even put a silica gel pack in the surge tank that slowly leaches out silicate to protect the cooling system, but mixing them still goes against the recommendation from the coolant manufacturer. I too would err on the side of caution and flush that sucker regardless of the MB service information... MB mistakes always morph into huge $$$$ bills.

Jasonoff

Converted to @BLKROKT 's favorite colour. The 2nd flush and it was dumping clear distilled water. Makes it easier with the thermostat bypass and smaller cooling capacity (no hvac or heated washer nozzle junk).