Why won't oil last in a marine engine?

[Nostrodamus]

You can put oil in a car engine and it will last 12,000 miles between services.
It is worked harder, at different and higher revs.

In a boat we are told it is important to change the oil nearly as quickly as we put it in.

Why is there such a difference?

 

[sailorman]

You can put oil in a car engine and it will last 12,000 miles between services.
It is worked harder, at different and higher revs.

In a boat we are told it is important to change the oil nearly as quickly as we put it in.

Why is there such a difference?

some say we change it too often which is unnecessary.
cars are normally x mls or y hrs which ever is soonest

 

[charles_reed]

An interesting point - I suspect oil technology and motor-manufacturers have been pushed by market demand into improving engineering and the oils so they'll go a longer period between changes.
Many mumble about the lower working temperatures of marine engines being unsuitable for the pressure and detergent additives in modern oils - but I do possibly perceive a big scam by marine diesel manufacturers and distributors to avoid their warranty obligations by specifying obsolete oils which are unobtainable and claim that all users have voided their warranties.
Then, of course, most modern diesel auto-engines are turbo-charged and have common-rail direct injection; few marine diesels have turbos and none, that I know of, have anything but pre-chamber mechanical injection.

So we suffer from the technological backwardness of marine diesel engine suppliers providing us with obsolescent products.

 

[savageseadog]

Boat engines are an outpost of marine conservatism, in my view quite rightly, simpler the better. The biggest issue with boat engines is lack of use and short intermittent running.

Coming back to the question, I content myself with one oil change a year, needed or not. I suspect that many engines never need an oil change in their whole lives.

 

[Blueboatman]

Small auxiliary diesel engines rust out before they wear out typically? Perhaps that has something to do it.
I am surprised at how small is the sump capacity on my Yanmar. Again, that would advocate shorter intervals between changes.
I 'suspect' (guess) that car engines suffer less condensation internally and are better temperature regulated once running. Prob work under load more too, which we are told is what you should always do with a diesel.

 

[Nostrodamus]

Last time I looked Volvo was not in the oil exploration game so they buy their oil from someone, stick a lable on and hike up the prices saying you should only use only their product. I don't know if there is a difference in a cheap or Volvo oil of the same specifications. I don't know if a synthetic or natural oil is best.
I am willing to listen to any argument.

 

[rafiki_]

An interesting point - I suspect oil technology and motor-manufacturers have been pushed by market demand into improving engineering and the oils so they'll go a longer period between changes.
Many mumble about the lower working temperatures of marine engines being unsuitable for the pressure and detergent additives in modern oils - but I do possibly perceive a big scam by marine diesel manufacturers and distributors to avoid their warranty obligations by specifying obsolete oils which are unobtainable and claim that all users have voided their warranties.
Then, of course, most modern diesel auto-engines are turbo-charged and have common-rail direct injection; few marine diesels have turbos and none, that I know of, have anything but pre-chamber mechanical injection.

So we suffer from the technological backwardness of marine diesel engine suppliers providing us with obsolescent products.

Most mobo engines are turbo's, and since 1990 DI, and since 2000ish common rail, so not so far behind the auto sector.

An oil change in my Beemer costs £140, and lasts 20000 miles, about a year. I change the oil in my 2 boat engines annually, cost me £35 for oil and filters last Saturday. It is a good idea to change annually as even with low hours, there will be contaminants from the diesel fuel get into the engine oil. Plus, over the winter, there will be a degree of condensation getting into the oil. For £35 it is one of the least of my costs of boating, so a no brainer.

 

[pyrojames]

An interesting point - I suspect oil technology and motor-manufacturers have been pushed by market demand into improving engineering and the oils so they'll go a longer period between changes.
Many mumble about the lower working temperatures of marine engines being unsuitable for the pressure and detergent additives in modern oils - but I do possibly perceive a big scam by marine diesel manufacturers and distributors to avoid their warranty obligations by specifying obsolete oils which are unobtainable and claim that all users have voided their warranties.
Then, of course, most modern diesel auto-engines are turbo-charged and have common-rail direct injection; few marine diesels have turbos and none, that I know of, have anything but pre-chamber mechanical injection.

So we suffer from the technological backwardness of marine diesel engine suppliers providing us with obsolescent products.

As almost all "marine" leisure engine are automotive derived there is a change to direct injection, turbo engines. Anyone with an old genuine marine Volvo engine, ie MD1,2,3 etc will be aware that they were also direct injection models. My engine is a aFord FSD, transit dervived engine from the early 80's and while it is does not have a turbo, it is DI.

Cummins MerCruiser are now using VW TDi engines, so the change is on the way, it is just that many boat engine are expected to last 20, 30 years? while road engines last about 10.

 

[Bilgediver]

You can put oil in a car engine and it will last 12,000 miles between services.
It is worked harder, at different and higher revs.

In a boat we are told it is important to change the oil nearly as quickly as we put it in.

Why is there such a difference?

Many marine engines contaminate the oil with water from condensation and fuel dilution from fuel pump spill. This affects the lubrication properties and so changing the oil frequently is the solution. There will be some engines run commercially with external fuel pumps etc that do not have these problems and run equivalent hours to your car.

Volvo oil is blended for them and I believe the main difference between it and Tesco's best is that the Volvo oil has rust inhibitors added. Cheaper to buy Tesco oil and change more often

 

[macd]

You can put oil in a car engine and it will last 12,000 miles between services.
It is worked harder, at different and higher revs.

In a boat we are told it is important to change the oil nearly as quickly as we put it in.

Why is there such a difference?

12000 miles at 30mph is 400 hours. Not all that big a difference.

 

[Stu Jackson]

? Difference between diesel engines and petrol engines? The diesel engines use the oil for cooling, too.

 

[Sans Bateau]

Modern car diesel or petrol engines run at high temperatures, these modern designs are compatible with the high tech fully synthetic oils that are now available. My diesel car gets a service with oil change every 22K.

25 - 30 years ago, cars had oil changes every 3,00 - 6,000 miles using mineral oil, old technology, just like most boat engines, which are even worse as they rarely get up to full working temp (except in the Solent), so there is more acid and condensation in the oil, so needs changing more often.

However, as I understand it, you should not use new tech synthetic oil in an old chugger as fitted in your boat, just in the same way if you put old tech mineral oil in your new car you will end up with a big repair bill.

 

[sailorman]

Modern car diesel or petrol engines run at high temperatures, these modern designs are compatible with the high tech fully synthetic oils that are now available. My diesel car gets a service with oil change every 22K.

25 - 30 years ago, cars had oil changes every 3,00 - 6,000 miles using mineral oil, old technology, just like most boat engines, which are even worse as they rarely get up to full working temp (except in the Solent), so there is more acid and condensation in the oil, so needs changing more often.

However, as I understand it, you should not use new tech synthetic oil in an old chugger as fitted in your boat, just in the same way if you put old tech mineral oil in your new car you will end up with a big repair bill.

as an aside -

my briggs & stratton 12 hp ride on mower uses 5>30 semi synthetic & runs much better then when i was using 15>40 my mistake

 

[fishermantwo]

The only real difference I can see between a yacht diesel oil change and that of a car is access to the oil filter. My yacht like many others has poor access to the filter and would benefit from a remote filter installation. Its a Volvo 7b. I've sold my fishing vessel now which was Garner powered. Oil dirtied up quickly but filter changes could be carried out easily. Mate is installing a GM 253 in his fishing boat and is chasing up a remote filter kit. The idea being to fit a new screw on oil filter once a fortnight. Cheap way to add a few hours to the life of the engine.

 

[Clyde_Wanderer]

Just changed the oil in my Perkins 10306, oil was last changed at start of season and was still a syrupy colour when drained even though I ran the engine more this summer than last.
Leaving old oil in during winter lay up can result in acid pitting.
I will drain and replace this oil again at the start of next season.
C_W

Fishermantwo, you obviousley havent worked on too many cars!
Some of them need an oil filter radar just to locate the filter!

 

[mocruising]

Explain this one to me some VP marine engine say change every 100 hours some say 200 hours both engines have turbo chargers Yanmar generally say 200 hours or all say once a season.

 

[reeac]

? Difference between diesel engines and petrol engines? The diesel engines use the oil for cooling, too.

Do you mean that petrol engines don't use oil for cooling? OK they seldom have an engine oil cooler but you can't prevent, for example, oil splash onto the underside of the pistons having a cooling effect.

 

[Sans Bateau]

Do you mean that petrol engines don't use oil for cooling? OK they seldom have an engine oil cooler but you can't prevent, for example, oil splash onto the underside of the pistons having a cooling effect.

There are though many differences between Diesel and petrol engines, and I think the one the poster means is that a petrol engine will run at a higher temperature than a diesel engine, but that is not because of the oil.

 

[sailorman]

I lifted this from the YBW a while ago


The only real way to know if you need to change your oil is by having it tested.
The cheapest test I could find on the internet was 22.5usd hence it's not cost effective on a small engine.
Re "acid" attack.
Diesel engine oils have an additive to give a reserve of alkalinity to protect against corrosion caused by the formation of sulphuric acid. This reserve is measured and called TBN, total base number.
Most diesel engine oils will have an initial TBN in the range of 10 to 30. This depletes in time and when it gets down to the figure recommended by the engine maker the oil should be changed, about 10.
The rate of depletion of the reserve depends on many factors, some being: sulphur content of the fuel, condition of the fuel injection equipment, condition of rings/liners, how often there is unburnt fuel, i.e. stop/start cycle, how much oil is topped up.
TBN is only one of many of the reasons you may need an oil change, other major reasons? Viscosity low, insolubles high, water content, flash point reduced or any combination.
So what should you do, well make up your own mind!
What do I do? Change once a year at the end of the season and run to check the filter is Ok. Stop it and leave it till next year. If I get to 200 hours in the season then I do a oil change plus at the end of season.
During running I check the level, wipe the dipstick on the back of my hand, smell the oil and then feel it between thumb and finger. (level to make sure its not increasing, look to check colour for water contamination, smell and feel for diesel contamination)

Over time depending on the operating conditions oil deteriorates.
This can be as a result of poor combustion/worn rings/water leaks etc.
Main items effected are
Viscosity, due to fuel or other contaminates
Alkalinity, due to acids
Insolubles, due to particulates

For engines with large sump volumes routine testing is used. Depending upon the results a complete or partial oil change may be required. Typically a medium size (1000KW) generating set on a ship, often runs with the same oil for periods of around 7 to 10,000 hrs.

Oil is typically stored on board ships for many years and there is no deterioration, no shelf life.

A large bore 2 stroke engine may contain 40 tons oil oil in the system, this initial charge may be in the engine till the ship is scrapped (100,000hrs or more).However it has continuous centrifuging and routine condition testing.


If you stop/start and idle or low power run, i.e. poor combustion conditions, this will be reduced. Hence some makers, for engines they know are going in small boats, quote very low oil change intervals.

If your engine maker states 50 hour interval then this covers the worst case scenario that they expect the engine to operate under.

If you change your oil, run above say 85% power and keep going then an oil change every 2 days is clearly daft!!

Hope this has helped!! Compared with the cost of repairs,the oil cost is small, so suggest you change as per makers advice and at least once a year.

 

[brianhumber]

Have a 25 year old XLD which is an industrial version of the standard Ford Escort diesel engine of the 80s.

Because I have done full anaylsis of the oil done over the nearly twenty old years I have owned the engine, I do not change the lub oil until it needs it.

The current sump oil is 4 years old and has not significantly degraded from new. I generally renew after 5 years or so. It seems some people on here would expect my engine after this to be shot, ie corroded, no oil pressure and fit only for scrap. Sorry to have to inform them the oil pressure is still very good after some 5,000 hours, the metal surfaces show no signs of pitting and engine runs and starts well without smoking of any colour. I would expect at least another 5,000 hours before bottom end overhaul required. Modern diesel engines aim for at least 25,000 hours now.

I am also responsible for several 40 and 50 year old diesel engines and the oil in these are between 5 - 10 years old currently and these engines run on traditional old specification mineral oils and on fuel to a poorer grade of Gas oil than the fuel available from Marinas these days. Again, anaylsis is the key player for the oil in these engines.

There might have been a case for changing oil more frequently when fuel was high sulphur etc but those days have long gone. Trouble is the text book and magazine authors have not caught up and still preach what they were taught or just read about decades ago. With such duff information still being prattled around is it any wonder non technical owners still change oil every year just in case.


Brian