Detroit diesels 671 multi grade oil or strictly 30/40 mono grade?

Bertramdriver

Bertramdriver

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One for Alf I guess. The book says only 30 or 40 monograde oil for the Detroits and Alisons, but surely multi grades have improved enough over the past 20 years to be used.
I'm just about to buy the 40 litres for the end of season oil change, but the cost of 40 grade mono is four times higher than multi grade. Hence the hesitation.
Is it reasonable to use multi grade and if so what is recommended for the warm water med?
 
We use 15/40 in our old fords, when new they needed series3 WHATEVER THAT WAS. I think a synthetic is a no-no, but you should be ok with a multi grade.
 
I would wait for Alf to come along, however in my book Detroit strokers do not respond well to multi viscosity oils, piston scuffing was always talked about, as sulphated ash content of four stoke lubes do not meet Detroit spec.
 
Latestarter1 said:
I would wait for Alf to come along, however in my book Detroit strokers do not respond well to multi viscosity oils, piston scuffing was always talked about, as sulphated ash content of four stoke lubes do not meet Detroit spec.
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Seems they like a low ash oil... CRB 40 and CRF 40 from Castrol where these engines are in abundance however I would speak to
Castrol MArine at 0843 258 2199 which is in Swindon and see what they offer as a low ash oil in the UK.

They will be supplying oil rigs in the north sea where these engines are fitted in elderly cranes.

Turner Diesel do DD reconditioning and parts from Aberdeen so also useful 01224 723 925,
 
Let me elaborate.... :)

I have been told by authoritative people on these engines that the single most cause of engine problems with the DD 71's is use of multi-grade engine oil. ie,15W40. These engines were designed to operate on straight weight engine oil ONLY 30W or 40W.This engine has cast iron full round pistons the running clearances (piston to liner) are very tight. Plus the inverted scraper type oil rings have a high tension abutment ring (similar to bottom right three in image below) which causes a "cutting or slicing action" to the oil. Multi grade oil cannot stand up to this type of abusive use, hence the failures when being used. OK in an emergency as a top-up and get home safely, but change quickly and definitely NOT for long term, or heavy load !!!

413328135_522.jpg
 
Divemaster1 said:
Any commercial supplier & brand, Shell, Exxon, Texaco, Sachs, Chevron, BP etc., do single grade 40 oil ... I get 40L for just above £120 (about £3 per litre), so should not be massively more expensive than multi-grade....
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Seems that DD also suggest low ash???? Is this a consideration or maybe not available....
 
Bilgediver said:
Seems that DD also suggest low ash???? Is this a consideration or maybe not available....
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All these have "Low Ash" and meet DD spec's. Remember, at peak there were 6,000 71 series built every month (http://www.dieselduck.ca/historical/01 diesel engine/detroit diesel/index.html#.UmRadeFwbIU). In 1967 they built the millionth..mid 70's two M..... and ... hundreds of thousands are still running in commercial applications, so there is still the need (and commercial drive) to supply the lube...
 
Divemaster1 said:
I have been told by authoritative people on these engines that the single most cause of engine problems with the DD 71's is use of multi-grade engine oil. ie,15W40. These engines were designed to operate on straight weight engine oil ONLY 30W or 40W.This engine has cast iron full round pistons the running clearances (piston to liner) are very tight. Plus the inverted scraper type oil rings have a high tension abutment ring (similar to bottom right three in image below) which causes a "cutting or slicing action" to the oil. Multi grade oil cannot stand up to this type of abusive use, hence the failures when being used.
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Far from claiming to be a DD expert, but in principle I can't understand why oil rings life should be much harder than in any other engine.
I would think that they should never reach the ports (as opposed to the compression rings), or do they?

But that aside, I don't get how can any engine be "designed" to operate only on single grade oil.
I mean, an engine can require an oil with certain specs, and one of them can be the viscosity of course - SAE 30 or 40, in this case (btw, I assume your "W" was a typo).
BUT, and it's a big but, the viscosity at operating temperature is NOT different between a SAE 40 and a 15W-40, for instance.
The differences (AOTBE) are only at low temperature, where the multigrade has a lower viscosity, hence a better pumpability.
Which can only be an advantage, in my books.
Actually, I'm aware that over the Pond there are still many single grade lovers, but I never found anyone who gave me a sensible explanation for that, other than something along the lines of "if it ain't broke, don't fix it"...

Of course, there are other specs which can be met or not by some specific oils (either single or multi grade).
A low sulphated ash content, as LS1 said, can be one of them.
But that's a different matter altogether - there are in fact low-ash multi grade oils.

Mind, I'm not saying that multi grade oil are fine for DD engines.
But if they aren't just because they are multi grade, I'd be curious to understand why exactly.
 
MapisM, I cannot give you any better explanation as to why ... I speak with people who run these lumps hard, service & re-build them and they all agree that DD Spec oil (mono-grade) is right for them ... there are cases out there where people have run some 71's with 15/40 and others with straight 40. The ones running on straight 40 (in same application) had on average 3x the run time before re-build than the ones running 15/40.

I am no expert, but as long as the recommended lube is cheaper than the alternative, I cannot see any reason for challenging several decades of experience and advise.. nor do I want to use my engines for a trial...
 
Divemaster1 said:
MapisM, I cannot give you any better explanation as to why ... I speak with people who run these lumps hard, service & re-build them and they all agree that DD Spec oil (mono-grade) is right for them ... there are cases out there where people have run some 71's with 15/40 and others with straight 40. The ones running on straight 40 (in same application) had on average 3x the run time before re-build than the ones running 15/40.

I am no expert, but as long as the recommended lube is cheaper than the alternative, I cannot see any reason for challenging several decades of experience and advise.. nor do I want to use my engines for a trial...
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Alf,

I can understand what MapisM is getting at........Years ago simple rule for DD was straight grade 30/40 with no greater than 1% Sulphated Ash, 15W40 was typically 2% Sulphated Ash so easy to understand. However some newer low saps multi grade lubes are now 1% Sulphated Ash. My guess is that these newer low ash multigrade lubes do not have additive pack with anti shear properties which DD 2 strokes require. Just a scientific wild assed guess (SWAG)

Hope this helps everybody.
 
After due consideration of the above I've decided not to run the risk of using my DDs as a test bed for multi grade oil. In Greece 40 mono may cost four times more than 15/40 but at least I can sleep at night. Funny isn't it. When you're sitting beside those great and seemingly indestructible lumps of steel, how something as simple as the wrong oil can bring them down. There's a moral there if I could only find it!
 
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Hi Alf, thanks for the advice. I suspect that the price difference has more to do with my engineers commission relationship with his supplier than the true price. Unfortunately Aegina is a small island, my boat is well known, and my engineer is in a monopolistic position. If I drive around the island looking for 40 grade, which nobody ever has stocks of, my engineer will know by the time I get back to the boatyard. However the quid pro quo is that his bills for labour are always surprisingly low. ONTH there's a plentifull supply of 30 grade which is used widely by the fishing boats. I could go for thinner but driving the DDs hard when the sea temperature is 25c seems like a recipe for over heating, especially as the oil forms part of the cooling system. Is 30 grade worth the risk?
 
MapisM said:
LOL, how did you think of it? I just love the SWAG concept. :)
I've seen SWAGs working better than academic theories, in more ways than one...
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Used to find engineering meetings dry humorless affairs which often needed a lift..

Thought of another answer to you question re-straight grade lubes Vs multigrade. Think of marine transmissions, very high oil shear applications, generally specify straight grade lubes.
 
LOL, I definitely see what you mean.
If that's any consolation, I can assure you that financial meetings are on par, if not possibly even worse...

Yep, I can understand why DD engines require a high shear strength oil.
Otoh, I've seen syntethic multigrade oils with a very high HTHS viscosity index used for very demanding performance engines (though actually petrol rather than diesel, but I think the concept should still stand).
Pretty sure, you can't buy those oils at a price anywhere near a good straight grade mineral oil.
Which at the end of the day is another good reason for choosing one or the other, once the specs are met...
 
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