oil changes between mercedes service

[Steve Hunt]

Originally Posted by Steve Hunt

Pull a oil sample, spend $20 and get the actual data to decide. I use Blackstone Labs for years on my tow vehicle, daily driver, race bikes etc. Engine oil, transmissions, diffs etc.
I can tell you that I would never go 20,000 miles on engine oil, the additive package would surely be depleted but that is the purpose of a oil analysis it will quantitatively tell you exactly. The report will also compare your engines oil data points to the database of their oil samples from other 3.0L diesels.

Here's a copy of the first oil analysis report I did on my 6.8L V10 E350. Notice the last data point...TBN which is the test to determine how depleted your additive package is and is used to decide if you can safely extend your oil change interval or not. I sent my oil sample in at 5300 miles and based on the TBN of 3.6 they are suggesting 7500 on the next change and then again. As long as you're greater than 1.0 you can continue to creep it out. I can tell you though that having done this many times it won't land much more than 7500 since I'm at 3.6 at 5300 miles now.

[Steve Hunt]

Originally Posted by mk216v

Definitely cut the intervals in half, at least. Off the top of my head (I don't have my cheat sheet in front of me), up to '14 was LOF's every 10k. In '15+ they stretched it to every 20k....why? One reason is that MBUSA can then market the costs of maintenance over your ownership as being less $ than it actually is, so it's more enticing for buyers to buy a new vehicle. Sneaky.

So True, BMW pulled a similar stunt in the 2005ish timeframe. They noticed they were getting a bad reputation for high maintenance cost so what did they do...Hey BMW owner all fluids are now "Lifetime" change intervals...how's that for cutting maintenance cost! But they kept using the same fluids and just changed the meaning of the word "Lifetime" as a normal person would define it. Lifetime became how ever long it last, when it fails, its life is over. BMW also knew the % of original new car owners that kept the car for decades or 100s of thousands of miles is basically zero so Lifetime fluids ie no maintenance/no cost is what people want to hear...let the next guy worry about it.
I had a 2004 530i and told them to change the transmission fluid, coolant and rear diff at 60,000 miles, they pushed back saying its all lifetime no need to change it. I went to a independent shop had it done and sent the samples in. The trans fluid was completely depleted and 50,000 would have been a better interval. The coolant was marginal and due. Interestingly the rear diff fluid was fine and the lab said it could easily have gone 120,000.
For interesting reference the 2004 530i had a 3.0L in line 6 and early on I just waited for the computer to say the oil life was up, that happened at ~12K miles at which time I sent a oil sample in....long story short i ended up doing 6000 mile oil changes based on the repeated oil samples. My 1995 Chevy C3500 6.5 diesel is at 7500 miles intervals and my 3.0L Honda accord with 377,000 miles got 8000 mile intervals.

[mk216v]

Yep!
"Lifetime" to the manufacturers means "After the factory warranty expires, we don't care what happens as we're off the hook. But if your engine and trans and rear diff blow, hopefully you bring it back to a dealership and pay us again--for replacements."