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Diesel motor oil? (LONG) Sludge problem?
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Posted by VIGGENmike (more from VIGGENmike) on Tue, 5 Jul 2005 10:34:12 Share Post by Email
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This is something I pulled of the Cadillac board. Please comment, can this help with the SLUDGE problem


"I am recommending the 15W40 Rotella/Delo/Delvac oils for the 44.1/4.5/4.9 because of two reasons: Those oils do NOT contain the friction modifiers that are found in oil marketed as "gasoline" oils these days and, more importantly, because those oils contain more of the anti-wear additive ZDP than is allowed in oils marketed as "gasoline" engine oils. The Rotella/Delo/Delvac oils are simply heavy duty oils. They also happen to meet all the diesel specs. They are not just "diesel" oils. They are a very high quality group of oils that meet multiple performance specifications for diesel AND gasoline engines. Read the bottles and see the specs listed and decide for yourself.

The confusion exists because of several reasons:

Years ago the shelf oils in the aftermarket did not meed the heavy duty needs of diesel engines...so each of the diesel manufacturers made their own oil specs and specified their own labeled oils for their engines. Diesels have special problems with temperature due to high loads and turbo charging. Diesels get soot in the oil. Diesels need special additives for cleanliness due to different blowby products. Oils that meet diesel needs are typically more expensive....so they did not make economic sense for gasoline engines. In addition, the popularity of the multi-viscosity oils that soared for gasoline engines further distanced the requirements of gasoline engine oils and diesel engine oils. The polymers used for the multivis oils caused severe ring belt deposits in diesels leading to specific "diesel" and "gasoline" oils. Diesel oils of that era were almost without fail straight weight oils with multi-vis allowed only in the coldest situations if at all.

Gasoline engines of the era did not put a lot of stress on the oil necessarily (certainly not like a heavily turbocharged diesel engine) and the quality or performance capability of the oils typically found on the shelf were heavily dicated by price. Gasoline engine oils of that era were typically performance rated as SC, SD , SE and SF in the early 80's....compared to SL in the progression of ratings that you see today.

Many years ago the autocompanies wanted to test on the EPA emission test for fuel economy label ratings with oils with friction modifiers for improved fuel economy. Friction modifiers in the oil can improve fuel economy 10% in some cases. The EPA would not allow this at first as the customer would likely not use the "fuel economy oils" in the field. So....the auto companies got together with the oil industry and oil industry groups and came up with the GF-3 specifications (now GF-4) that required that the oil meet all the current performance standards AS WELL AS contain fuel economy improving friction modifiers. If you read the can of engine oil you will find the starburst GF3/GF4 symbol and the GF3 or GF4 rating listed. As well you will see ratings like "SL" and words to the effect of "fuel economy improving" oil. Those are on the most common shelf oils in the discount stores and such.

Additionally, the amount of antiwear additives in the oils has slowly been reduced over the years. One of the components of the anti-wear additives is phosphorus (the other is zinc). ZDP is the additive and it stands for zincdialkyldithiophosphate. Phosphorus, unfortunately, poisons catalytic converters so the general direction is to limit the ZDP content in the oil to protect the cat converters in the vehicle fleet. Fortunately, most all the modern engines are designed to run with very little ZDP in the oil. Changes to the engines such as roller followers, roller rocker arms, roller cam chains, gerotor oil pumps, eliminating distributors and distributor gears, etc. all make the need for ZDP to protect the engine less important. So the new, GF3/GF4 oils work fine.

The 4.1/4.5/4.9 engine family dates back to the very early 80's so some of the design predates all this. Roller followers were added to the 4.5/4.9 which helps as well as a gerotor oil pump to the 4.9. But they all still contain an oil pump driven by the distributor gear (high load/high wear potential) and rubbing element rocker arm pivots (high load/high wear) that like more antiwear protection....such as a lot of ZDP.


Summing all this up...???.....the multi-vis additives have gotten much better these days as the viscosity improvers are all synthetic polymers. They are SO good that they even work in diesels. Hence the Rotella/Delo/Delvac oils commonly available as 15W40 that meet diesel specs (read the can for all the specs). The "diesel" oils ALSO meet the gasoline performance specs (look for the SL performance rating on the can of Rotella/Delo/Delvac). The "diesel" oils do NOT contain the friction modifiers....hence they are not rated GF3/GF4 "for gasoline engines". The "diesel" oils DO have more antiwear additives since they are intended for the heavy duty use, they need the added anti-wear additives to meet all the stringent diesel specs and they are not restricted by the GF3/GF4 gasoline engine requirements.

Soo....the Rotella/Delo/Delvac brand names are really names for a very good, very high performing group of oils that offer excellent wear protection in weights suitable for gasoline engine use in varied coldstarting conditions. They also happen to meet all the diesel specs. They are simply good oils...not "just" diesel oils that are specifically for diesels. The diesel requirements (all the CL and CI and CF ratings and such on the bottle) dictate the majority of the performance specs (so they are commonly know as diesel oils) and the inclusion of the SL rating indicates the oils ALSO perform in the gasoline engine tests as Sx ratings indicate gasoline engine testing. The oils are also marketed as "diesel" oils in a bit of cooperation with ILSAC and the API so as to differentiate them from the "gasoline" oils labeled GF3 or GF4.....gasoline oils that have lower levels of the anti-wear additives and include the fuel economy enhancing friction modifiers.

My advice to use them in a 4.1/4.5/4.9 is driven by my desire to see people use the "best" oil in them that will make them last as long as possible and offer the best service. Any of those engines will likely run fine on most any oil but the "diesel" oils will offer more protection in the event of an irregularity or circumstance that might tax the limits of the conventional oils.

How old am I...???...LOL...over the hill if that means anything to you. As far as the veterans...I have well over 30 years as an engineer in the automotive industry working primarily on engine development so I don't know that that qualifies me as a veteran but in the process I have come across a LOT of information about oil....

If you haven't been subjected to the hype that Amsoil creates around their product then you must not read any car magazines or go to any automobile related events. Amsoil banners seem to be everywhere and even the home improvement shows always have an Amsoil salesman in his booth with his little displays of parlor magic proving the "superiority" of Amsoil. Due to their chain of sales and distribution and dealers and salesmen and suppliers, etc....they are simply a pyramid marketing scheme that uses oil to enrich everyones pockets in the food chain. They offer no superior products. Their products are not necessarily bad.....just the same quality and performance is on the shelf at WalMart for 1/4 of the cost.

Reading the specs on the bottles of oil will tell you a lot of this. Spend 10 minutes in the oil isle at WalMart and bring your reading glasses....unless you are young enough to not need them....LOL.

As far as putting "diesel oil" in a "car"....what if the "car" had a diesel engine??? Oil is oil. It is formulated for a specific use and labeled as such. In many cases the specifications for diesel oil and gasoline engine oil overlap and/or if the oil meets one it can meet the other. The key is to look at the specifications for the oil. "diesel" oil circa 1980 would NOT meet gasoline engine requirements and would not be speced or labeled as such. Conversely, the answer to your question is on the can of Delvac.....the SL rating indicates it was tested and works fine in a gasoline engine...as well as the diesels indicated by the multiple Cx ratings. That is how I can easily recommend "diesel oil" in a "car"...LOL LOL

Hope this answers your question. "

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