drewsolace

Hey guys, first post here so bare with me. Need some fast emergency answers.

I have a mechanic I trust that I implored to change the oil in my 2018 c43 AMG. However, I guess he was in a hurry and drained the front diff fluid on accident. He re-filled the diff with 75w-90 fluid. I have since found out that the car takes 75w-85. I am worried that maybe I should cease to drive the car immediately and have it towed to my nearest mb/AMG center to have them assess and replace with the cirrect fluid.

Am I over thinking this? Is the car safe to drive. Needing answers ASAP please.

Grateful for any and all response.

TModelle

Dont worry about it. It’s fine.

Just get it changed out again to the proper spec. You can drive with 75w-90 for awhile. You don’t have to tow it.

drewsolace

Appreciate the fast answer, apparently one of his guys says MB recommends .55 liter capacity for that front diff so that is what he did. That sounds like barely anything to me, but im no mechanic. Still okay?

TModelle

0.55L is correct.

TModelle

To be honest, if they used a GL-5 gear oil you should be fine.

drewsolace

Once again, thanks so much for the prompt replies. He used Mobil 1 Synthetic 75w-90 API GL-5. Would you care to let me bother you with exactly what the difference is between the 75-85, and why it is the only one listed as compliant on the MB bevo?

RichardCranium3

In oils, the first number is the "cold" viscosity, second number is operating temp viscosity, e.g., at start up, the oil flows like 75 weight, at operating temp, it flows like 90 weight. MB likely just set their standard that 85 was the optimal operating viscosity. I'm not a transmission expert, but I did stay a holiday inn last night - you're okay to drive, but if anything funky starts to happen, this should be order of business numero uno, and corrected on your mechanic's dime. Meanwhile, I might suggest another mechanic while you're at it. In the mechanics world, confusing diff and oil pan is busch-league mistake.

jonathan358

Is changing front diff fluid even necessary? I spoke with an MB Service Advisor and she told me that the open differentials for 4Matic don't need changing, i.e. lifetime fluid.

Also confirming 0.55L is correct.