Why Rotella?

[Administrator]

What is it about Rotella oil that provokes uniformly positive recommendations? And while while I'm at it, what's special about "diesel" oil, and should we care?

Bill

[ndutton]

I listen to a car tech radio program every Sunday morning and this subject was discussed just yesterday. Well, not diesel rated oils in particular but the advantages of zinc in the oil for older engines with flat tappet cams. Without carrying on ad nauseum here's a link discussing it. In the paper ZDDP is mentioned often. ZDDP is zinc dithiophosphate found in most diesel rated oils.

There's a mention about its (zinc's) elimination in auto oils due to some issue with catalytic converters.

[hanleyclifford]

I don't possess the same level of technical expertise as Neil, but I will only say this: since switching to the Rotella 15-40w my engine runs noticeably quieter, and more readily maintains oil pressure throughout heat and rpm ranges. FWIW

[Chris G]

Any advantage to using a synthetic oil?

[Ball Racing]

Depends, you want to make sure it is approved for wet clutches if you do.

[Mo]

Diesel oil has shear properties as well designed for hard use....worth looking up what all the lettering means. These engines are not tight tolerances compared to modern gas engine designs...so shear properties are a definite asset.

[hanleyclifford]

I suspect that many oil pressure issues on this forum are related to the mixed clearances of our engines. Often A4s are rebuilt to clearances of .001" or .0015" at the crank and rods while the cam bearings are allowed to drift out to .0025" or .003". A lot of pressure is lost at cam bearings. Such diversity creates wide oil pressure ranges due to temp and rpm changes.

[CalebD]

Subjective answer

The previous owner of our boat (who had it in his family for about 20 years) told me to use Rotella T 30W oil in the engine when he sold it to me 10 years ago.
Since then I have read Nigel Caulder's "Boatowners M&E Manual" where it specifically talks about oils and their API ratings. While it is true that Rotella T is one of the few oils that are rated for diesels it is also one of the most highly engineered oils for 'spark' engines as well as 'compression' engines.
I also like the fact that this oil is meant to be used in a nasty, dirty diesel engine and handle all the associated soot produced in the compression ignition process. I know that my A4 is not nearly as sooty or dirty as a diesel but it makes me feel good that my 45 year old engine can burn a little oil and not upset the viscosity of the oil too much.
Not all oils are created equal. Look at the API (American Petroleum Institute) ratings for all the oils in an auto parts store sometime. The ratings vary considerably and some are barely suitable for modern auto engines.
Buying a good oil is cheap insurance.

[Sony2000]

Another aspect of diesel oil is that it has a "low ash" content. That should make it have greater lubricating properties, and leave more room to suspend the carbon bits?

[Carl-T705]

Rotella has the highest ash content of all diesel oils. CAT recommends not using Rotella, but if the owner insist to change the oil more frequently. If you're looking for oil with all the good stuff in it go to race engine oils.