Is Diesel Grade Motor Oil Necissary When Running Biodiesel??

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Krank
Diesel Freak
Posts: 171
Joined: Wed Jul 05, 2006 10:49 am
Location: Hillsboro, Oregon

Is Diesel Grade Motor Oil Necissary When Running Biodiesel??

Post by Krank »

So there I was, puttering in to work this morning and I had a thought...
I know, I know I should mark this day down on the calander, right?
Anyhow, since I've always heard that the reason I need Diesel motor oil in my engine is to nuetralize the acid content caused by sulfers in the fuel, I have to wonder if I need diesel grade motor oil any longer. Is there any other reason to run the expensive diesel version? My rabbit hasn't seen diesel in a year and a half and isn't expected to any longer. My Audi is on track to mimick the Rabbit. I just don't run diesel, and don't plan on it.
Can someone in the motor oil industry or some sort of knowledgable chemist chime in as to why I need to continue with the expensive stuff? I'd really like to run a gasoline synthetic in order to get the benifits of synthetic as well as the affordability.
Any input??? Anyone???
'81 Rabbit N/A
'82 Audi 4000 Diesel (a vw in luxery clothing!)
Powder Hound
Glow Plug
Posts: 1
Joined: Fri Sep 12, 2008 8:51 am

Post by Powder Hound »

There are a number of 'synthetic' oils available for diesel use. Group III base oils (hydro-processed dino oils) are considered synthetic since Castrol was taken to task for claiming their g-3 oil was synthetic and won before the FTC. Castrol, Pennzoil, Chevron (who owns the process and licenses it out) among others all use g-3 base oils but consider them synthetic. There's others, e.g. Rotella or Delvac that may be in the same boat, or might be group IVs (aka PAO or polyalpha olefins). I haven't checked closely on them because I haven't used either of those two.

Personally, I prefer Redline diesel. Even though it is a little thicker at 15W40, I feel it is a much better product and the price differential isn't that bad to me. Its main base is a group V, an ester, which has better shear strength, temperature stability, and film strength than any other base. It is nearly impossible to press it out of the bearings when the engine is not running, unlike any g-3 or g-4 base oil. Add to that a strong TBN and soot dispersant package, and you have a long drain oil that will do very well for you.

You really ought to use a diesel oil for bio-d for the same reasons you use it for dino-d. The combustion cycle in a diesel engine is still going to be producing some soot, and the acidic combustion by products are going to be present still. The nitrogen NOx compunds that blow by the rings, mix with water vapor from combustion still form acids the oil must neutralize, even if the nitrogen doesn't come from the fuel (which it doesn't in either fuel). So you're going to need that soot dispersant and TBN additive package no matter what fuel you use.
You always pay for what you get. Sometimes, you get what you pay for.
Krank
Diesel Freak
Posts: 171
Joined: Wed Jul 05, 2006 10:49 am
Location: Hillsboro, Oregon

Post by Krank »

WOW!
You're some kind of smart on this stuff, aren't you? Honestly, without some sort of cross reference for what you wrote, i was lost in many of the acronyms and chemical references. I can say that I was greatly impressed, and regardless of my inadequate background to fully comprehend everything you put out there, I did get the jist of it and will do some research to find the redline that you spoke of. I know I already use their tranny fluid, and have always been pleased with it.
I appreciate the feedback. Anything I can do to elongate the lifespan of my buggies is always a boon. Thanks for sharing your wealth of information!
'81 Rabbit N/A
'82 Audi 4000 Diesel (a vw in luxery clothing!)
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