Detroit 2-strokes requiring mono-grade

[AP9]

I don't drive anything with a diesel, but I've been wondering about this.

Why exactly did the Detroit Diesel 2-strokes (71 series, 92 series, etc.) require mono-grade oil? With improvements in HDEO basestocks since these engines were developed, is it still a bad idea to run multi-weight oils in them, even 15w40?

 

[artificialist]

Detroit Diesel said that VIIs were going to varnish the engine. Also, monograde oil sometimes have a much different add pack from 15w40. CF-2 was created with a lower SAPS because the Detroit 2-stroke burned so much oil. If there was a higher SAPS, the combustion chamber would get severe deposits.

It would be interesting to see what could happen if a fully synthetic 15w40 CJ-4 oil was used. Minimal VIIs and a low SAPS additive package. It would be an expensive experiment due to the large oil capacity, and constant oil burning.

 

[Shannow]

There was a lot of resistance to multigrades from the big manufacturers of diesels in the early days, probably for a couple of reasons.

Firstly, the polymer VIIs meant that there was both temporary shear loss and permanent shear loss that reduced the possible hydrodynamic lubrication.

Secondly, the polymers when they broke up were prone to sludging, oxidation and deposits.

They resisted, and relented on 15w40 as a reasonable compromise for some/many.

The 2 strokes I could see them not liking VIIs for deposits etc. as the oil has greater access to gasflows.

 

[Fleetmon]

We've used 15w40 in a couple of older snow blowers we have with 8V92's (8V92 for the blower engine and a Series 60 for motive power) and both Planemates which are equipped with 6V53's (the gen engines are 3-53's). They use a LOT of oil using the multi-visc....probably close to a gallon an hour on the blowers. Once we go back to SAE 30, oil consumption falls to about one quart per hour.

 

[Doug Hillary]

Hi,
AP9 - All two stoke Detroit Diesels were specified a mono-grade - even into the last of the 92s (TTA). A SAE 40 was the prime viscosity with a minimum of HTHS vis of 3.7. A 15w40 or SAE 30 was allowed for short periods when ambient temps were in the range -18 to -32C. The SA max is 1 and in used oil analysis the soot max is 0.8%

A SAE 50 lubricant should be used in temps above 35C

These engines ingest a lot of air and high oil and fuel consumption was/is always a feature of these engines. In the correct application they are durable and the 92TTA was a great engine with minimal oil consumption and reasonable fuel use due to the unit injectors and ECM. Of course they sound great too at "full song"

For the skilled technician they were easy engines to rebuild - well, up until they joined the electronics age at least

For me a Euclid-Terex V12 dozer pushing a TS24 (twin engine - V8, V6) Terex scraper in a borrow pit is a lasting memory!

 

[NMP]

I worked for a fleet that had over 100 71 and 92 series Detroit Diesels. The Fleet Manager decided to switch from straight 40 to 15w40 "because its new and better". Two things happened: first, oil consumption went up. Second, we began to burn exhaust valves.

These engines have 4 valves per cylinder and compared to the Cummins and Cat motors of the era they were very small. Where the standard Cummins engine had 855 cu. in. out of 6 cylinders the 8V-71 was 568 cu. in. out of 8 cylinders. The physical dimensions of the cylinders limited valve size. On teardown we found significant deposit buildup on the valve stems. Once enough deposit accumulated the valve would stick and allow the combustion flame to travel across the seat. It didn't take long to 'flame cut' a slot on the valve face.

We had never experienced valve hang up on straight 40 but 15w40 was a disaster.

 

[Shannow]

Good info guys, thanks.

 

[supercity]

Originally Posted By: AITG
I worked for a fleet that had over 100 71 and 92 series Detroit Diesels. The Fleet Manager decided to switch from straight 40 to 15w40 "because its new and better". Two things happened: first, oil consumption went up. Second, we began to burn exhaust valves.


How long ago whs that and what lube was it? How do you think a CJ-4 lube would go?

 

[A_Harman]

Originally Posted By: Doug Hillary
Hi,
AP9 - All two stoke Detroit Diesels were specified a mono-grade - even into the last of the 92s (TTA). A SAE 40 was the prime viscosity with a minimum of HTHS vis of 3.7. A 15w40 or SAE 30 was allowed for short periods when ambient temps were in the range -18 to -32C. The SA max is 1 and in used oil analysis the soot max is 0.8%

A SAE 50 lubricant should be used in temps above 35C

These engines ingest a lot of air and high oil and fuel consumption was/is always a feature of these engines. In the correct application they are durable and the 92TTA was a great engine with minimal oil consumption and reasonable fuel use due to the unit injectors and ECM. Of course they sound great too at "full song"

For the skilled technician they were easy engines to rebuild - well, up until they joined the electronics age at least

For me a Euclid-Terex V12 dozer pushing a TS24 (twin engine - V8, V6) Terex scraper in a borrow pit is a lasting memory!


Is there any truth to the statement that the Detroit 2-strokes never needed to have the oil changed because of the large amount of top-up oil that was necessary? I used to hear that one a lot when I worked at Cummins.

 

[Doug Hillary]

Hi,
A_Harman - Well the OCI intervals of course were mandated by DD at from 4k to 8k miles and up to 150hrs depending on application.

I was involved with the largest Fleet of DD powered (71s and 92s) KWs in the Southern Hemisphere - around 100 trucks involved in Livestock, Car Carrying and General freight. The biggest fear was "dusting" especially in Outback use. Air filters were sometimes cleaned daily and Livestock drivers carried spares. They all carried a gallon of oil (SAE40). We never used SAE50 even in desert type operations. "Jake" brake weren't too effective in some applications either.

In another Fleet of KWs we had around 30 with 71s then 92 TTAs. Poor fuel economy eventually killed their use in this type of operation. The TTAs were quite light on oil use IIRC - we used used oil analysis to determine OCIs here and I think we got to around double the DD recommendations.

Castrol RX 40 was the preferred lubricant in DD two strokes in these years and still is by all accounts!

Each Fleet kept a spare rebuilt engine (each series) ready for quick installation

But then Cummins had their issues - remember the L10 and M11 Series?

 

[A_Harman]

Yes, but no first hand experience with those engines. When I first started working at Cummins (1990), president Henry Schacht gave a talk to the new-hires in which he gave a short company history from the early 70's. The L10 was a very different engine compared to the NT when it was introduced in 1982. It had mid-stop liners and high cam placement, and was designed for higher cylinder pressure. They tried to market it as a class 8 truck engine, but many truckers thought it was too small. I think the main problem with that engine was head gaskets?

I thought it was a strange engine when I first looked at it, but came to like it as I understood more about its design. Cummins had a turbo-compound version of the L10 almost ready for production in 1991, but pulled the plug on it. Maybe they were tired of innovating? This was when the top rated L10 was 360 HP, and the turbocompound version had 400, so it wasn't very aggressive for power enhancement. But an engineer I knew from the project said it made 400 HP on the same fuel flow as the 360 HP base engine.

When I started there, Cummins was still trying to recover from the injector carboning warranty issue on the NT 444. That was such a bad problem, they had to take on bank debt to pay the warranty claims, and was a drag on profitability for many years.

 

[The_Eric]

Wow! Thanks to both Doug Hillary and A Harman for contributing!

 

[AP9]

Originally Posted By: The_Eric
Wow! Thanks to both Doug Hillary and A Harman for contributing!


+1

 

[skellyman]

One key thing to remember , the oils spec'ed for 2 cycle Detroits will be a CF-2 while many will say it's obsolete in API specs this is simply not true if your using it in the Detroit 53 , 71 ,92 , 110 series engines.

 

[Garak]

And Mobil (and others) still offer products that they recommend for such use.

 

[Brent_G]

Great info! We just bought two M1070 with 8V92's in them and I wasn't sure if 15w40 would be fine or not.

 

[bullwinkle]

Mobil Delvac 1300 carries the CF-2 spec in 15W40-but straight 40 would still be better.

 

[NMP]

Originally Posted By: A_Harman


Is there any truth to the statement that the Detroit 2-strokes never needed to have the oil changed because of the large amount of top-up oil that was necessary? I used to hear that one a lot when I worked at Cummins.


About the same time we were having problems with 15W40 and burnt valves, Detroit Diesel came out with a 60,000 mile oil drain. Two things supposedly allowed this: first, add oil kept replenishing additives and second, the blower pressurized the crankcase. This kept a supply of filtered air inside the oil pan and kept out impurities. The engines had two drains that let any moisture that condensed in the airbox drain to the atmosphere.

At the same time DD recommended the extended drain, they came out with a modified air box drain system. Instead of 'drooling' the moisture to the atmosphere it dumped it into the oil pan.

It appeared that engineering group A never talked to engineering group B. I ate a lot of square meals - not to mention buying a couple of nice houses - thanks to Detroit Diesel. We used to say "If there's oil in it, there's oil on it".

 

[NMP]

Originally Posted By: Doug Hillary
Hi,

For the skilled technician they were easy engines to rebuild - well, up until they joined the electronics age at least


I started my career rebuilding 53 and 71 series Detroits. I got pretty proficient at it and also had the benefit of learning what was critical (liner height, head bolt torque) and what wasn't so much (valve bridge adjustment).

When I tore down my first Mack ENDT 675 I realized that there were more parts in a 6-71 cylinder head than there were in the whole Mack engine. I never rebuilt another Detroit.

 

[Doug Hillary]

Hi,
AITG - Yes you make a good point. I said this above;

"In another Fleet of KWs we had around 30 with 71s then 92 TTAs. Poor fuel economy eventually killed their use in this type of operation."

The vehicles mentioned in here were replaced by Macks' with Maxidynes. They were taken up on a Contract Maintenance deal - their fuel economy was excellent and they were reliable over the 4 year Contract operating 24hrs 5 days per week and totalling around 700k kms. They were hauling coal (38 tonnes) mainly downhill loaded so it was an easy life. Their superior torque changed driving habits too

I was never a Mack fan although I did a good survey (in 1986-7 with Mack Trucks) of several Mack users in NYC mainly in the Waste business. The Fleet Owners loved them with a passion

Blower drives could be a problem on DDs too - but you'll know that of course