Engine Oil - Bristol Sleeve Valves

[Simon Thomas]

Does anyone know what the secret sauce was in the oil for the Bristol sleeve valve engines?
The specification was D.E.R.D. 2472 A/2, B/2 or B/0. Apparently Aeroshell 100 U met the specification.

The "Lubricants and Special Fluids" book by V. Stepina, V. Vesely in section 5.2.1 states: "The old types of oil were dosed with ash-producing additives (e.g., under British specification DERD 2472B/2) but they were not widely applied." Based on this I gather that it isn't an ashless dispersant oil like W100, more like straight 100 with a particular additive package.

There are very few references that I could find, but it appears that the oil is no longer made and the sleeve valve engines need it.

 

[Crimea_River]

We run a Hercules at the museum and I can ask what they use next time I'm down.

 

[kmccutcheon]

Does anyone know what the secret sauce was in the oil for the Bristol sleeve valve engines?

The following manual excerpts may be helpful:
From Centaurus 661 Maintenance Manual dated Jul 1950

From Hercules 730 Maintenance Manual dated Jun 1952

From Hercules 264 Maintenance Manual dated Feb 1968

Looks as if there are still numerous oil choices for persons operating sleeve-valve engines.

 

[mad_max]

This reminds me of someone that was supposedly working on the 190 White 1 restoration telling me they didn't know how they were going to get fuel to run the engine as no one manufactured fuel from coal tars anymore. I had to chuckle and told him 100LL would work fine as it's rating was atleast 100/130 and many times was 103-4 lean and 130+ rich. I even asked the person heading up rebuilding the 801 and was told 100LL works just fine with alittle change in the injection system.

There's always going to be ways to get around problems, if there really is a problem.

 

[Simon Thomas]

Thanks Kim. From that list it appears that the correct spec aero engine oil is easily obtainable.

I still wonder what was in Aeroshell 100U that is different to 100.

 

[kmccutcheon]

I still wonder what was in Aeroshell 100U that is different to 100.

Send a query to Ben Visser
[email protected]

 

[Simon Thomas]

I didn't hear back from Ben.

I found some information.
In the paper "A History of Aircraft Piston Engine Lubricants" by Robert V. Kerley
SAE Transactions Vol. 90, Section 3: 810614––811014 (1981), pp. 2601-2628 A History of Aircraft Piston Engine Lubricants on JSTOR
it states:

In the same paper, Bass states that tri-cresyl-phosphate was used in Bristol Hercules engines to alleviate corrosion of cadmium alloy big-end floating bushes.
Ogston (39), states that Bristol sleeve valve engines used D.T.D. 472 straight mineral oil until 1943 when Paranox 56, a barium compound, was specified in order to alleviate ring sticking and especially sticking of the junk head ring at the top of each cylinder. It would seem that the Hercules engines used both tri-cresyl-phosphate and Paranox 56.

The Bass paper referred to is:
E. L. Bass. "Piston Engine Fuels," Centenary Journal of the Royal Aeronautical Society, Vol. 70, No. 66), Jan. 1966, pp. 166.

Ernest L Bass, FRAeS, , Director of Aeronautical Research of the "International Shell Group," retired. He also represented the British Air Ministry on Subcommittee for Fuels and Lubricants, NACA, during a period of W.W. II.

The Ogston reference is to personal letters. Ogston is Alexander R. Ogston who worked for Exxon.
He wrote the paper "A Short History of Aviation Gasoline Development, 1903—1980". A Short History of Aviation Gasoline Development, 1903—1980 on JSTOR

Be warned, the Jstor collection of SAE papers will absorb many hours.
There are papers by Heron, Fedden, Doolittle, Mead, Nutt, Hives, Riccardo, Jacobs, Colwell (Valves) and many more.

 

[Simon Thomas]

Mitasol kindly posted a Hercules manual dated March 1947 (excerpt below). It states "At present either Shell" zinc-dips" or Intava IAA.SlO detergents can be used."
In "ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY FOR 1945", it states that "Zinc dips" is Zinc salt of diisopropylsalicylic acid.
In US patent 2,258,591 (1939), the Shell inventors "claim as our invention: A compounded mineral lubricating oil of improved anti-corrosive properties containing a small amount of the zinc salt of di-isopropyl salicylic acid."
The patent introduction states "It is known that in modern internal combustion engines, such as high speed Diesel engines, aviation gasoline engines, etc., which due to their high power output, operate at relatively high temperatures, piston rings have a tendency to become stuck in the grooves."

I expect that as this 1947 manual only lists AeroShell 100B, that must be the one that contains the zinc additive.
The oils listed in the manuals further above also include AeroShell 100U, which is likely the one that has the barium additive.
Edit: Aeroshell W100 comment removed.

 

[Trilisser]

It would be interesting to test modern fully-synthetic oils in these engines, especially those intended for high-performance diesels in which the oil is under very harsh conditions not unlike in large aero engines. Someone will scream "they are not aviation approved", but the engine doesn't know it.

 

[Simon Thomas]

Full synthetic oils and air-cooled engines don't mix.

Mobil AV-1 Under Attack

A class-action lawsuit demands that thousands of TCM 470-, 520-, and 550-series engines that used Mobil AV-1 synthetic oil be grounded for tear-down inspection and overhaul at Mobil's expense. We urge owners not to panic.

www.avweb.com

Exxon Elite oil was pulled from the market in 2019, and it was only 30% synthetic. It had numerous issues with sludge formation.

 

[ThomasP]

Interesting article. I wonder what the actual chemical deterioration and/or lubrication process failure is.

From past (admittedly limited) experience I do not see that synthetic oil (with appropriate additives) should have any more problems than non-synthetic. Also, synthetic oils are usually better at handling higher heat loads while maintaining lubrication than non-synthetic oils.

Not saying the article or its premise is wrong, I just have not in the past run across anything chemical or otherwise technical in nature that would account for the apparent problem.

 

[Simon Thomas]

The best explanation I have read for the synthetic oil failure from someone who actually knows aviation oil is here:
Edit - it needs a login.
Link for those with a BeechTalk login : BeechTalk - Login

I used AI to reword:

The primary issue with Mobil AV1 stemmed from a misunderstanding by its formulators regarding the distinct requirements of automotive versus aircraft engines. Unlike automotive engines, aircraft engines impose different demands on oil due to factors such as thermal stress in auto engines and contamination in aircraft engines. Air-cooled aircraft engines, unlike water-cooled automotive ones, are designed with larger clearances to accommodate a wide temperature range (-40 to +500 degrees F) and varying coefficients of expansion between materials like steel and aluminum.​

​

These expanded clearances result in significant blow-by fuel entering the oil, with most being expelled through the breather while a fraction remains, oxidizing and becoming reactive. This blow-by fuel is the primary cause of deposits in aircraft engines, as the oxygen atoms in the molecules render them acidic, leading to the formation of deposits on metal surfaces.​

​

Dispersants, which are key additives in oils, play a crucial role in preventing deposit formation by binding to acids and keeping them dissolved in the oil until drainage. However, dispersants do not address lead particles, wear metals, or dirt, nor do they affect break-in.​

​

The choice of base oil is also pivotal, with mineral base oils aiding dispersants in solubilizing deposit precursors effectively, thus prolonging dispersant effectiveness. Synthetic base oils like polyalphaolefin (PAO), however, do not solubilize acids, diminishing the dispersant's efficacy over time.​

​

Mobil AV1, formulated with PAO as its base oil, encountered issues due to its inability to solubilize organic contaminants effectively, leading to deposit formation and engine failures, especially in conditions mirroring stop-and-go driving rather than steady cruising.​

​

While Mobil AV1 initially performed adequately in commuter aircraft, broader usage revealed its shortcomings, resulting in engine failures and subsequent legal action. While PAO base oils excel in automotive applications, they are ill-suited for air-cooled aviation engines.​

​

Ultimately, the failure of Mobil AV1 can be attributed to a lack of comprehension regarding its intended application.​

I recommend reading the BeechTalk version, but this one avoids copyright issues.

 

[Engineman]

Thanks for the posts and links about aviation piston-engine lubrication oils. Certainly, this subject remains important, particularly for operating Vintage engines. It is apparent that many lubrication requirements are very specific, the Bristol big-end bush being one. Additionally, low utilisation can see oils in engines for long periods, unforeseen by original engine designers. One factor that I note is that the contaminants in a large engines oil build quickly. Operating the DB605 I completely changed the engine oil every autumn, just before the Winter servicing and inhibiting, so the oil never did more than about 20 hours. That job also left fresh oil in the engine during the lay-off.

Eng

 

[MIflyer]

By the way an A&P friend of mine found out the hard way that Aeroshell W100 Plus oil has an additive in it that is required for some Lycoming engines but in certain Continental engines it causes the starter drive coupling to slip. This is also a problem for the Aeroshell semi-synthetic 15W50 oils, which also has that additive. So maybe for sleeve valves they use something like that.

 

[Trilisser]

The Avweb article gives reasoning that is the exact opposite which have been observed with especially fully-synthetic oils optimized for high-performance diesels used in older petrol (car) engines: these cases have found the oils to be very "washing" which has caused the dirt in the old engines being quickly washed away and then the sludge has caused problems. Solution: short initial oil-change periods.

It is also perverse that when the obvious solutions for the use of non-leaded fuels exist (including ADI), some still cling to it leaded fuels. These people are like those in automotive world who vehemently opposed the introduction of unleaded gas in cars and who invented fantastic stories how good the lead was. When these people were told that originally there was no lead in gasoline, their mouths went silent.

 

[MIflyer]

Shell admitted that the partially synthetic mult-vis Aeroshell is so thin at lower temperatures that it drips off of the engine parts and provides less corrosion protection.