Rotella T for gas motors? Is this OK?

Being a diesel guy I've got a case or two of Rotella T (15-40 I think) oil. Is it OK to use this in our 96 E320 with 155k on it?

[mbdoc]

As long as the oil has an API classification of SJ then yes!~!~!

[stephenson]

Seems like 15-40 is a bit thick for a late model gas engine ...

Comments?

[loubapache]

15W-40 should be fine in Hotlanta.

The viscosity scale is not linear. For example it sounds like a 15W-40 oil is 50% thicker when cold than a 10W-40 oil but it really is not.

According to API,

a 5W-xx oil should have a maximum low temperature cranking viscosity of 6600 cP at -30 deg C.

a 10W-xx oil should have a maximum low temperature cranking viscosity of 7000 cP at -25 deg C.

a 15W-xx oil should have a maximum low temperature cranking viscosity of 7000 cP at -20 deg C.

Since it is not linear, it is hard to compare on a linear scale (the scale we are used to). Some oil experts said, if forced to say it, that a 15W-xx oil is really like a 12W-xx oil if it is compared linearly.

[stephenson]

Good points, however, my understanding was that:

1. Should use thinnest oil recommended by manufacturer
2. Because newer engines have lower tension rings, are built to closer tolerances, etc.

[loubapache]

stephenson:

If you take a look at MB's approved oil list for new cars (from 98) and recommended for old cars, there is no oil that is of the x(x)W-30 variety (among these available in the USA). As a matter of fact, it specifically says that Mobile 1 Tri-synthetic 0W-30, 5W-30 and 10W-30 should not be used (too thin).

[stephenson]

loubapache,

You are absolutely correct ... my concern was the W number not the operating temperature number.

What do the 2000 and newer models call for? Same? US and other Euro/Jap cars seem to call for thinner W and operating temp numbers?

[loubapache]

stephenson:

I have not seen a more updated list so I guess the latest one still holds.

The MB dealers use Mobile 1 Tri-Synthetic 0W-40. I read an article somewhere that people were compaining that the 0W-40 was a bit too thin at operating temperature to protecting the engine so Mobile changes the formula a bit to thicken it up.

The Old Mobile 1 Tri-Synthetic 0W-40 (SJ) has a kinetic viscosity of 13.5 cSt at 100 deg C.

The new Mobile 1 Tri-Synthetic 0W-40 (SL) has a kinetic viscosity of 14.4 cSt at 100 deg C.

As you can see, it thickend up quite a bit at 100 deg C. By the way, the 40 deg C viscosity number increases as well. In other words, the new 0W-40 is thicker than the old one when cold.

[stephenson]

Good data - thanks for the follow-up.

Have you been able to find the 0W-40 in L where you live?

I assume it is Compression (diesel) rated, as well? I have been trying to find DelVac One, but only time I have it was $6.50 a quart ... seems a bit silly at that price.

[loubapache]

<<
Have you been able to find the 0W-40 in L where you live?
>>
Not in stores but the Mobile distributors carry them about $5/qt.

<<
I assume it is Compression (diesel) rated, as well?
>>
The 0W-40 is only CF rated.

<<
I have been trying to find DelVac One, but only time I have it was $6.50 a quart ... seems a bit silly at that price.
>>
You can order from http://www.avlube.com/

$81.39 for a 4-gal case.

I forgot to mention that the number before the W in an oil cannot be looked at in isolation. For example at 40 deg C,

Mobile 1 Tri-Synthetic 5W-30 has a kinetic viscosity of 53.0 cSt;
Mobile 1 Tri-Synthetic 10W-30 has a kinetic viscosity of 59.0 cSt;
Mobile 1 Tri-Synthetic 0W-40 has a kinetic viscosity of 80.3 cSt.

So at 40 deg C, the 0W-40 is considerably thicker than either 5W-30 or 10W-30. API only specified the minimum and maximum value for a particular viscosity so anything in the range is good as far as the standard goes.

[stephenson]

Got it and I understand better.

Will try avlube, too.