Rotella T6 5W-40, 3,640 and 8,147mi, M-B 1995 E320

[AMRoberts]

For reference, a T6 VOA is here.

Took advantage of last year's Rotella rebate to get this oil into the inventory. My goals were: more ZDDP than the Mobil 1 10W-40 HM I had been using and at least marginally thinner oil.

The 3,640mi sample didn't surprise me much. Given what I've read here about wide-range oils shearing, Mobil 1 0W-40 becoming a heavy 30-weight with use, etc., I was expecting some viscosity drop.

My target for this interval was only 7,500 mi, but when I got there work and personal schedules made it look like it might be a good bit longer before I could do an oil change. Since I was about 0.5qt down, I went ahead and topped up. Somewhat to my surprise, schedule and weather cooperated 600 mi. later, allowing me to pull a sample and then change the oil.

This sample did surprise me. Viscosity increasing to greater than the value seen in the VOA is not a good thing, correct?

 

[Quattro Pete]

Originally Posted By: AMRoberts
Viscosity increasing to greater than the value seen in the VOA is not a good thing, correct?

I wouldn't lose sleep over it. According to spec sheet, this oil starts at 14.2. Chalk up the difference between UOA and VOA to lab test inconsistencies. Your insolubles are low and none of the wear values seem to be out of whack, at least to me.

Just curious, so the sample taken at 16K miles on 10/07/10 was M1 HM 10w-40? Looks like the oil did well there, despite the top ups.

 

[AMRoberts]

Originally Posted By: Quattro Pete

Just curious, so the sample taken at 16K miles on 10/07/10 was M1 HM 10w-40? Looks like the oil did well there, despite the top ups.


It was. I don't know what oil the previous owner was using. When I purchased the car it was probably using 1qt every 2000 miles. I changed to the Mobil 1 10W-40 HM; Counting the initial change and my, "rolling oil change" (I was extracting oil and adding fresh, those numbers are not just topping-up lost oil) I went through 16qts of Mobil 1, plus three oil filters.

So in that sense it may be more accurate to consider it two 8K intervals worth of oil, instead of a single 16K interval.

My intent for all the fresh oil was to see if the seal conditioners in Mobil 1 HM would help with the leak. Along the way my mechanic noticed the timing chain tensioner (oil pressure-driven) was broken, and it was replaced. I also learned about a factory TSB recommending reducing the fill amount from the owner's manual 8qts to 7.5qts, because the 8qt fill caused leaks.

Some combination of seal conditioning, repair, and learning not to overfill has reduced my leakage, so I stopped going through the cost and effort of the rolling oil change.