Oil for Diesel in my Gas Engine...

[TooSlick]

The Rotella T synthetic always almost shears a bit in turbocharged engines - as does every other, 5w-40, Group III synthetic on the market. Since this engine will function perfectly fine with a shear stable, xw-30 oil, the shearing isn't an issue.

These analysis results are fine, you could safely increase your service interval by 50% and still have plenty of safety margin. I would consider upgrading to a higher efficiency, high capacity oil filter if you chose to do this....

TS

[Bimmer]

Seabass, I didn't add any oil. It might have lost/burn a little bit, but not enough to show up on the dipstick.

TS, I'm tentatively planning to run the Mobil 1 0w40 that's in there now longer, though I only have one of the dinky OEM black oil filters installed — I think I might to go to an RX8 filter next time and save the little black ones for my NA Impreza.

I'll sample it at 4,000 miles to see how it's doing (using the Fumoto, without draining it all), and then when I have the analysis I'll decide whether/when to change it.

Originally Posted by bluesubie

Yeah, like lab error.

Lab error? Have a look in the uoa forum at bitog and you'll see a recent RT6 uoa from an STI for comparison (compare additives).

I know that the margins of error/tolerances on these lab tests are pretty loose, but these numbers just seem weird.


These are waynelewis's analyses, Rotella T6 in a STi after 4,000 miles, posted on BITOG:

CALCIUM 842
MAGNESIUM 1178
PHOSPHORUS 1068
ZINC 1289
cSt @ 212ºF 13.38

Same driver, same car, after a 5,000 mile OCI:

CALCIUM 1174
MAGNESIUM 1189
PHOSPHORUS 1112
ZINC 1347
cSt @ 212ºF 13.04

Same driver, same car, same oil, after a 5,300 mile OCI:

CALCIUM 752
MAGNESIUM 1135
PHOSPHORUS 980
ZINC 1125
cSt @ 212ºF 13.25

All of these have more Magnesium, Phosphorus, and Zinc than my sample, though his Calcium seems to oscillate a lot.
All of them have more viscosity, too.

I've also attached another analysis from BITOG here, and his Rotella numbers are also consistently different in the same way:
more Mg, Ph, Zi, about the same Calcium, and higher viscosity (13.0+).
(Never mind the analysis on the far right, that's not Rotella.)

I'm going to send Blackstone a note and ask about this...

Bimmer

[TooSlick]

I wouldn't worry about additive levels. These show up even after they have been rendered inactive through use.

The viscosity test is accurate to within +/- 0.2%, so the viscosities are very accurate. Fuel dilution also has a major impact on viscosity. Short trip driving in cold weather is the worse as far as fuel.

The Mobil 1, 0w-40 will shear too, as you'll see.

TS

[Bimmer]

Thumbs up for Blackstone's customer service:

I received an e-mail this morning saying that they would re-run the test. I received new results and an explanation and an apology this afternoon – at least they were upfront about having messed this up.

Says Blackstone:

Amended report. The additives were indeed low, and we actually re-ran this sample three times to see what was going on. It was a calibration problem, and for that we apologize...


New results are 10-20% higher across the board:

Moly 79
Ca 922
Mg 914
Ph 994
Zi 1056

cSt 12.47


Thumbs down to Blackstone's analysts:

It's awfully disconcerting that their calibration can be off by 10-20% or more and they don't realize it until a customer asks questions.
I wonder if they're going to revisit the other analyses which they did with the mis-calibrated equipment (I doubt it).

It's also disconcerting that it didn't occur to whoever did the initial analysis that the additive levels were abnormally low...
It took me all of 5 minutes to see that something was fishy (to find a bunch of UOAs of 5w-40 Rotella run in Subarus on BITOG and compare them to mine).
Blackstone must have thousands of UOA results, and they're supposed to be pros. Sigh.

Finally, they really did say "Nice engine" at the end of the new analysis. I'm not kidding. I'll post it once I black out my personal info and scan it in again.

Originally Posted by TooSlick

The viscosity test is accurate to within +/- 0.2%, so the viscosities are very accurate. Fuel dilution also has a major impact on viscosity. Short trip driving in cold weather is the worse as far as fuel.

I could understand that my oil sheared down to a 30-weight, but I still don't understand why mine did and the guys running Rotella in WRXs and STis still had viscosities of 13.0+.

It's not cold here, and I had just completed a 1,700+ mile road trip with this car, and my fuel contamination is listed as <0.5% (which seems to be as low as anybody ever gets). I'm confused...

BTW, in the new results viscosity is a full 1% higher. That's not enough to make any real difference, but it's more than double a ±0.2% margin of error.

[bluesubie]

Do I win a prize?

Even HDEO 40 grades are not shear proof. I wouldn't worry too much about it unless your wear is also high. If you're really concerned, you'll have to step up to something like Dyson Analysis for his guidance or switch to another oil.

I switched to Oil Anaylzers Inc. because you get more for your money, and without the excessive comments like, "Wear increased a little and your fuel dilution is a bit high. Add 3,000 miles to the next interval. Nice Subaru!"

-Dennis

[Bimmer]

Originally Posted by bluesubie

Do I win a prize?

Yes. Come out to California, and I'll buy the first pitcher of beer.

In all earnestness: Thank you. It was your suggestion to look at other UOAs on BITOG that prompted me to question Blackstone's results, which prompted them to run the analysis again...

Originally Posted by bluesubie

Even HDEO 40 grades are not shear proof.

I know, and I'm not really worried about it, but I think it's weird that Rotella sheared more in MY sample than in the similar UOAs posted. It wouldn't bother me if most UOAs of Rotella showed this much shearing. It bothers me that only mine does.

[bluesubie]

You're welcome!

I used to see similar comments about M1 TDT 5W-40. People would rave about how robust it is and that it never shears. Then a Forester XT owner at subaruforester.org ran it and regularly did uoa's in his stock FXT. It sheared something like 2 out of 3 times. I guess it's just the variances in driving conditions, driving style, individual car, etc.

-Dennis

[TooSlick]

If the additive levels are reading 20% too low, then so are the wear metal concentrations. Both are determined by using a mass spectrometer and ICP...

How much shearing you get depends on how hard the engine is drivin, the average/peak, oil temps and the # of fuel dilution. It can vary significantly from engine to engine, even within engine type. If you ran this oil significantly longer, it would start to thicken back up due to oxidation/nitration and evaporation of the lighter & more volatile components of the base oil & additives. A sample of oil with 4000 miles or less will almost always be thinner than when it was put in. As the oil degrades, the flashpoint will drop - with or without excessive fuel in the oil.

TS

[Bimmer]

Originally Posted by TooSlick

If the additive levels are reading 20% too low, then so are the wear metal concentrations. Both are determined by using a mass spectrometer and ICP...

Yep, but the wear metals were basically nil, they're still basically nil (see the attached revised analysis).

Originally Posted by TooSlick

How much shearing you get depends on how hard the engine is driven, the average/peak, oil temps and the # of fuel dilution...

Yes, this is the part I don't understand. My wife drives this car very moderately, and then we took a long sedate road trip, and my oil wound up shearing more than the WRX drag racers over on BITOG.

This doesn't keep me up at night, it's just a bit of a mystery to me.

[joewildlife]

rather than using synthetic 5-w-30 year around, what should I use for 5000 mile oil change intervals in my 2.5L normally aspirated Outback

1) in the winter when the piston slap makes babies cry and old men stare?

2) in the summer when I'm pulling 80mph mountain passes with a load and a couple canoes on top in 3rd gear for extended periods of time?

1) to quiet the thing down
2) so I don't blow it up.

Joe