Non detergent oil

April 5th, 2009

What happens when an old engine is introduced to detergent oil. I've always heard it is a No-No! Is this of interest to anyone else?

Cheers, Mossiyjack

Owen_Dyneto · April 5th, 2009

What MAY (or may not) happen is exactly what you'd expect if you think about it a bit. Depending on the engine condition there is the possibility that the detergent can dislodge old sludge and residue and circulate it thru your engine. Whether you want to try it or not, anyone buying a collector-type car who doesn't know the recent engine history should drop the oil pan and clean it, the pump intake screen, and other accessible areas thoroughly before doing their first oil change. Once the system is relatively clean, it's a much easier and less-risky choice about oil types.

Trunk Rack · April 5th, 2009

Disappointing that even today there is a common mis-conception about "detergent" and "multi-grade" oil.

Folks, please, those terms were products of the ADVERTISING folks who were in charge of getting you to BUY the stuff. Those terms have NOTHING to do with the real world of oil chemistry.

It is true that in the first few years (late 1940's) they had some problems with sludge dissolving. That was over by the early 1950's. THERE IS NO SUCH THING AS "DETERGENT" oil. It is an ADVERTISING phrase. What "detergent" oil REALLY means, is that thru chemistry, they have figured out a way so that the molecules that FORM sludge can not link up. Use it and your motor will not sludge up. Has NO effect on EXISTING sludge any different from ANY oil. NONE. If you start using a badly sludged up engine, ANY oil may act as a solvent & loosen up sludge.

"SINGLE GRADE" is actully "multi-grade", in that it has dramatic changes in viscosity as it warms up. It can be thick as sour cream when cold, meaning if you start your motor at zero F with 30 W oil, it will be too thick to lubricate, and you will damage your engine. It is ONLY the advertised grade at around 210 degrees. Above that, and it can get thin as water, causing damage.

So called "MULTI GRADE" oil simply means you can use it at ANY temp. within its design limits and those 'spec'd" by the engine manufacturer. Thus MULTI GRADE oil will flow at its rated grade at extremely cold temps, providing you with safe "start up" lubrication, but not THIN OUT at extremes of temp.

It never ceases to amaze me how many back-yard mechanics with only a high school course in physics and chemistry (if that) think they know more about this subject than the graduate chemical engineers and mechanical engineers who design these things.

Owen_Dyneto · April 5th, 2009

"but not THIN OUT at extremes of temp."

Really, show me a viscosity vs temperature plot that demonstrates that, please. What really occurs is that it thins less with heat than oils formulated without viscosity index stabilizers.

Trunk Rack · April 5th, 2009

of course OWEN is absolutey right - my sentence SHOULD have had the additional wording, to the effect that so called "mutli-grade" oils do not thin out at "ANYWHERE NEAR AS BADLY AS SO CALLED "single grade" oils."

Bluesky636 · April 6th, 2009

Originally Posted By: Trunk Rack

of course OWEN is absolutey right - my sentence SHOULD have had the additional wording, to the effect that so called "mutli-grade" oils do not thin out at "ANYWHERE NEAR AS BADLY AS SO CALLED "single grade" oils."

So what oil company do you design motor oil for? Frankly, after reading your post, I think you don't have a clue what you are talking about.

foxhole · April 6th, 2009

must be nice to have so little going on in your own life that you can sit on your computer and belittle someone that is trying to help others by imparting information, you should be nice to people or karma will give you cancer.

Originally Posted By: Bill_Haegele

Originally Posted By: Trunk Rack

of course OWEN is absolutey right - my sentence SHOULD have had the additional wording, to the effect that so called "mutli-grade" oils do not thin out at "ANYWHERE NEAR AS BADLY AS SO CALLED "single grade" oils."

So what oil company do you design motor oil for? Frankly, after reading your post, I think you don't have a clue what you are talking about.

Bluesky636 · April 6th, 2009

Originally Posted By: foxhole

must be nice to have so little going on in your own life that you can sit on your computer and belittle someone that is trying to help others by imparting information, you should be nice to people or karma will give you cancer.

Originally Posted By: Bill_Haegele

Originally Posted By: Trunk Rack

of course OWEN is absolutey right - my sentence SHOULD have had the additional wording, to the effect that so called "mutli-grade" oils do not thin out at "ANYWHERE NEAR AS BADLY AS SO CALLED "single grade" oils."

So what oil company do you design motor oil for? Frankly, after reading your post, I think you don't have a clue what you are talking about.

Ummm, so you believe and agree with the statements made by Trunk Rack about "detergent motor oil," "so-called single grade oil," and "so-called multi-grade oil?" If so, then perhaps both of you should do a little research into motor oils and what these terms mean.

And no, I am not a motor oil specialist but I have done my research and understand what these terms mean and anyone who has would never describe them the way Trunk Rack has. So no, I don't believe that he knows what he is talking about. If he does, he has communicated that knowledge poorly.

Trunk Rack · April 6th, 2009

Originally Posted By: Owen_Dyneto

What MAY ..... anyone buying a collector-type car who doesn't know the recent engine history should drop the oil pan and clean it, the pump intake screen, and other accessible areas thoroughly before doing their first oil change. . . . .

= = = = = = =

Excellent advice, especially for older cars without "full flow" oil filters.

OWEN - I would go further and say "dropping the pan" should be MANDATORY before starting ANY engine you have just aquired and are not familiar with its history.

ESPECIALLY if it has been sitting for a while, and/or hasn't had its pan "dropped" recently. And ESPECIALLY if it is from an "in line_ engine with a long oil pan, and/or the big "super power" multi-cylinder pre-war cars. That stuff WILL NOT DRAIN OUT from the drain-plug hole.

With all those big long flat internal spaces, stuff builds up. Many of these older engines do not have "floating" oil pump "pick-ups".

I personally think it is a wise shop proceedure to "drop" the oil pan on a older in service "collector car" at LEAST once every two or three years and clean it out. These older motors do not and can not "burn" as "clean" as a modern motor. So it is inevitable that crap builds up down there.

The only point of disagreement I have with OWEN's excellent post, is his suggestion this is relevant to "detergent" oil only. NO NO NO... If there is sludge build-up, especially in an engine that hasn't been run for a while, and the stuff has started to "flake" and dry up, ANY driving with ANY hot oil WILL act as a solvent and start loosening it.

Owen_Dyneto · April 6th, 2009

Peter, referring back to your earlier comment...."THERE IS NO SUCH THING AS "DETERGENT" oil. It is an ADVERTISING phrase. What "detergent" oil REALLY means, is that thru chemistry, they have figured out a way so that the molecules that FORM sludge can not link up".....

You are technically incorrect on this point though perhaps you're hung up on semantics. The property you describe, preventing the particles from forming a sludge, is accomplished by formulating a dispersant into the oil, and dispersing agents are of the large general family of detergents. The dispersants allow particulates to remain "in suspension" in the liquid phase and then ultimately to be removed by the filter.

I spent many years as a research chemist in the detergent area, trust me on this.