Diesel Engine Design Life

[coenvanwyk]

My experience is with older motor vehicle engines, at least one of which was also used in marine versions. I have never had problems with synthetic (mostly Shell Helix) oil in older engines, except where the seals were already hard. Synthetic oil cleans up the inside, with the result that seals may begin to leak. And, most importantly and most expensively, the residues and 'varnish' loosened by synthetic oil once plugged the oil feed to a turbo. When I explained the unexpected tubo failure to the mechanic, his first question was: "Did you f*** with the oil?"

On a diesel I would also be inclined to look for Shell Rosella, an old standby due to its additives being good for older style valve gear.

Whatever oil is used, I would not leave it in the engine longer than a year. I believe that, irrespective of the hours done by the engine, the additives in the oil begin to break down and acid begins to form after a year. One could have the oil tested, but it is so expensive for a once-off, as compared to changing the oil, that I would rather pay for fresh oil and filters than risk the engine.

Your mileage may vary.

 

[grumpy_o_g]

As in a Rootes 1750cc petrol engine
Damned valve was a short length of capped tube with a spring for tension. A bit of dirt would get in it & it would stick open & the engine would loose oil pressure
I do not suppose many can remember the Humber Sceptres & Hunters etc

I not only remember them, I had a Chrysler/Rootes Humber Sceptre and, not long after I bought it, knackered the big ends on a long and fast run to the UK and back from Laarbruch. I never expected it to use so much more oil than it did when I was doing shorter runs It was a far cry from the Humber Hawk and Super Snipe estates my father owned 20 or so years earlier.

 

[chrishelen]

This cant be correct. What about all the marine engines in fishing boats that log 5000 hours per year. Clearly these are the same engines. My own Perkins engine says change oil every 500 hours or annually. Clearly you would be changing the oil ten times per season when fitted to a fishing boat.

I change mine every 250 hrs or every six weeks, it has a hard life running for hours on end at 2200 revs (perama). It's my gearbox I worry about more than the engine, it's a zf5 and not designed for the usage it gets on this boat, I change the gb oil every 100 hours, it only holds nearly a litre so no hardship.

 

[Heckler]

I change mine every 250 hrs or every six weeks, it has a hard life running for hours on end at 2200 revs (perama). It's my gearbox I worry about more than the engine, it's a zf5 and not designed for the usage it gets on this boat, I change the gb oil every 100 hours, it only holds nearly a litre so no hardship.

Interesting talking about the vp gear boxes, my md2030 with the ms2 said use engine oil. This md22 i have now, which was 5 years younger, still with the ms2 box, says use 75/90 multigrade synthetic gl5. Oh and change it every year! It holds less than a litre so not a hardship.
S

 

[PaulJS]

I've just checked our 30+ year old Caterpillar D399 generator engine running hours for the end of the month...

Two of the six are over 89, 000 hours... Due for an overhaul at the next dry dock in 2019! Should each average about 1 years running by then...

 

[[159032]]

For balance, there are odd cases of <=60's engines where synth oil will escape from seals made from cork or leather or some such.

Castrol make Classic oils spefically to answer the older engine problems

WHY USE CLASSIC OILS ?

The formulations required for modern vehicles are very different from those needed for older vehicles. Oils for modern engines comply with the latest API ratings of SN/CF and specific ACEA and OEM specifications dealing with fuel efficiency, extended drain intervals and aftermarket exhaust treatment systems and are specifically designed for the modern engine needs.

A classic car engine however, can have the opposite characteristics with cork/graphite/rope seals, low pressure gear driven oil pumps, larger oil galleries with greater dependence on "splash" and "cling" lubrication, lower revving with larger machine clearances. Such a widely different engine design can demand a totally different lubricant and the Castrol Classic Oils range offers formulations for older vehicles that have been specially blended for the work they have to do.

 

[ghostlymoron]

As far as type of oil for a marine diesel, I would refer to a) the engine handbook and b) Morris oils technical department. The latter have oils specifically for old tech diesels.
Back to the original question, I've had 2 Volvo Penta MD1s which date from 1967. Both are still running at nearly 50yrs old. (Spares are hard to get though)

 

[vyv_cox]

b) Morris oils technical department. The latter have oils specifically for old tech diesels.
)

Unfortunately they don't do API CD, which is the oil recommended for most engines up to about 2005. I use their API CC for the BMC 2.2 diesel in the motorsailer, which may date from 1973. Half of it drips out and the rest burns off, so it probably doesn't matter much what I use.

 

[Trundlebug]

Unfortunately they don't do API CD, which is the oil recommended for most engines up to about 2005. I use their API CC for the BMC 2.2 diesel in the motorsailer, which may date from 1973. Half of it drips out and the rest burns off, so it probably doesn't matter much what I use.

My recommended oil spec is API CD too.
The nearest I've found recently is some Comma which is CG.
I recently bought 4x 25L which should last me 5 years.
I did come across some CD oil sold by an agricultural / tractor dealer, but it was too pricey.

 

[Kelpie]

I bought a bunch of CD spec off eBay, enough to last about eight oil changes...

 

[chrishelen]

Bandq were selling mineral oil API cc/cd the other day for £8 a gallon. yes gallon.

 

[davey]

when i re engined 13 yrs ago with a Nanni 4150 i asked a few plant operators about these Kubota engines, they had engines with 6,000 hrs with only routine servicing ever done. no major defects

Allegedly the engines that drive the refrigerator on lorries that carry frozen food will run OK for well over 10,000 hours. They never have timing belts as far as I know as thirty tons of frozen beef is far too valuable to trust to a timing belt. Usually over-sized aluminium sumps are used on the engines as well as over-sized oil filters. The small OEM sumps are discarded and replaced with ones that hold at least a gallon of oil. Its not rocket science!

 

[fisherman]

http://www.exol-lubricants.com/automotive/products/details/?PID=40
£42.
Mermaid tell me to worry when oil consumption is 2% of fuel consumption. At the moment I might use a litre between changes at 200 hours, which is about 1000 litres. At 12000 hours on the engine there is more loss from minor leaks than burnt.

 

[KellysEye]

>Don't worry, that assertion by KE has been repeated many times and rejected by the majority of forumites on every occasion.

I see you still haven't called Volvo to check what I said, nor has anyone else who has posted here, probably because you will all be proved wrong and have to admit it. I don't doubt that well looked after engines can last longer if of well looked after but if Volvo say the design life of modern engines is 8,000 hours I believe them, why should they lie.

 

[fisherman]

>Don't worry, that assertion by KE has been repeated many times and rejected by the majority of forumites on every occasion.

I see you still haven't called Volvo to check what I said, nor has anyone else who has posted here, probably because you will all be proved wrong and have to admit it. I don't doubt that well looked after engines can last longer if of well looked after but if Volvo say the design life of modern engines is 8,000 hours I believe them, why should they lie.

...ermmm to get you in the mind to buy another?

 

[NormanB]

As in a Rootes 1750cc petrol engine
Damned valve was a short length of capped tube with a spring for tension. A bit of dirt would get in it & it would stick open & the engine would loose oil pressure
I do not suppose many can remember the Humber Sceptres & Hunters etc

I can.
Changed that valve - and the mains, large ends small ends and rings. Did it in a long weekend and did another 75,000 miles before I sold it. (Humber Sceptre - G Reg 1969). Loved that car.

 

[jdc]

>Don't worry, that assertion by KE has been repeated many times and rejected by the majority of forumites on every occasion.

I see you still haven't called Volvo to check what I said, nor has anyone else who has posted here, probably because you will all be proved wrong and have to admit it. I don't doubt that well looked after engines can last longer if of well looked after but if Volvo say the design life of modern engines is 8,000 hours I believe them, why should they lie.

I think there is a factor which you may not be taking into account: the speed (rpm) of the engine. The life of bearings for instance is calculated as number of revolutions. So immediately one can see that 1 hour at 2800 rpm is equivalent to 2 hours at 1400. Hence when Volvo tell you a figure for life, there must be an implicit assumption about its average rpm; presumably they assume something quite high?

The next, and probably more important factor is that the number of revolutions a bearing can be expected to last is a function of the dynamic load, in fact about (1/load)^3. We can assume for the purpose of illustration that the load in the main bearings is proportional to shaft horespower being delivered. This power is approximately the rpm squared, so engine life will then be proportional to 1/rpm to the power of:

1 for the conversion from rpm to hours, plus
2 for the relationship between rpm and dynamic loads, plus
3 for the relationship between dynamic load and expcted number of revolutions the bearing can endure.
----
6

An amazingly strong function! Life proprtional to (1/rpm)^6!!

So a factor of 2 in engine service rpm can lead to a factor of 2^6 = 64 in life expectancy. Hence one can't just take the Volvo number of 8000 hours at face value; it has to depend to some extent on service conditions.

Of course, bearings are not the only part with finite life, piston rings probably last a shorter time but then these can be replaced quite easily and so wear-out of these would not necessarily condemn an engine.

 

[Daydream believer]

I can.
Changed that valve - and the mains, large ends small ends and rings. Did it in a long weekend and did another 75,000 miles before I sold it. (Humber Sceptre - G Reg 1969). Loved that car.

I had a new one for my 21st birthday prezzie. ( The hunter version) It was my second ( the older vogue version which was flasher) & they were brilliant
Had the head off both of them.
Could not do that on my current vehicles, Not that i would want to somehow!!!

 

[TQA]

Allegedly the engines that drive the refrigerator on lorries that carry frozen food will run OK for well over 10,000 hours. They never have timing belts as far as I know as thirty tons of frozen beef is far too valuable to trust to a timing belt. Usually over-sized aluminium sumps are used on the engines as well as over-sized oil filters. The small OEM sumps are discarded and replaced with ones that hold at least a gallon of oil. Its not rocket science!

30,000 plus is not unusual and I have seen some with 40,000. Perkins 4108s mostly.

 

[reeac]

I think there is a factor which you may not be taking into account: the speed (rpm) of the engine. The life of bearings for instance is calculated as number of revolutions. So immediately one can see that 1 hour at 2800 rpm is equivalent to 2 hours at 1400. Hence when Volvo tell you a figure for life, there must be an implicit assumption about its average rpm; presumably they assume something quite high?

The next, and probably more important factor is that the number of revolutions a bearing can be expected to last is a function of the dynamic load, in fact about (1/load)^3. We can assume for the purpose of illustration that the load in the main bearings is proportional to shaft horespower being delivered. This power is approximately the rpm squared, so engine life will then be proportional to 1/rpm to the power of:

1 for the conversion from rpm to hours, plus
2 for the relationship between rpm and dynamic loads, plus
3 for the relationship between dynamic load and expcted number of revolutions the bearing can endure.
----
6

An amazingly strong function! Life proprtional to (1/rpm)^6!!

So a factor of 2 in engine service rpm can lead to a factor of 2^6 = 64 in life expectancy. Hence one can't just take the Volvo number of 8000 hours at face value; it has to depend to some extent on service conditions.

Of course, bearings are not the only part with finite life, piston rings probably last a shorter time but then these can be replaced quite easily and so wear-out of these would not necessarily condemn an engine.

I have some doubts about the above. For simplicity let's confine ourselves to crankshaft bearings as jdc has done. The analysis ignores the concept of a threshold engine speed below which there may be negligible wear ..analogous to the situation with fatigue damage. Such a threshold might be 1000-1500 rpm in a typical small marine diesel. I agree that higher rpm risks increased wear rate but my guess is that that increase is pretty small up to 2500 rpm and only becomes serious near the maximum design rpm. Anyway let's hear from the "Italian Tune Up" advocates.
My own VP 2002 dates back to 1987 and I have a Kubota tractor of 1983 vintage ..don't know their engine hours.