does engine oil deteriorate with time or just use?

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blueglass

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I know the standard wisdom is that we should change engine oil every year, regardless of the actual engine hours clocked up, but isn't this a bit of a waste? Surely the oil breaks down and loses its lubricational properties etc as the engine runs, but if it is just sitting in the sump for most of the season, then it I'm thinking it can't degrade in any way. Ok I have a motorboat and this is a major expense hence my query. I'm thinking that with an average of 100 hours or less each season, then I am throwing away perfectly good oil? I stand ready to be contradicted.
 
You may be right - but there is also the matter of acids, moisture and carbon that get their way into the oil ... these degrade the oil. They can cause problems with bearings and surfaces.

But I think we can all quote a known boat / person that hasn't changed oil and still running fine ! My Suzuki Vitara ran for about 5 yrs on no service or oil change - sold it one openly informing the buyer that was the case and advising a service / oil change. He came back to me later and said that all was fine and appeared ok.
My boat - albeit a motor-sailer but engine works quite hard on her - didn't have oil change for 4 years ... changed it out here and kept the oil back for ref. Apart from being jet black viscosity was ok .... but note I never tested for acids / alkalis, sediments or moisture - so don't take it as passed !!
 
The more regularly the engine is used is a good thing! Cold starts really degrade the oil and are not much good for the engine! I'm pretty sure oils degrade over time because they come with a proper seal when you buy them, especially in an engine when there will be lots of contaminants from combustion.
 
My engine is a perkins 4-108 which recomends using 20 - 50 multigrade which I can buy for £5 per gallon so I consider it a cheap insurance to remove any acids from the engine which must be a good thing. I change the oil and filter at the end of the season, and change the oil alone half way through the season. As I have a hand pump permanently in the sump it is clean and easy. Only takes a few minutes.
 
Would agree with everything Refueller has said.

I did a couple of formal tests when I first had the yacht but results came back saying all levels were fine. I now pump out a small bottles worth of oil every year to let settle and see if any water appears at the bottom of bottle etc. Oil tends to last arund 5 years and 21 year engine still going strong with good oil pressure, no signs of corrosion on cam or emulsification.

Others who change their oil every year are now on replacement engines but they are Volvo so what can you expect.

Brian
 
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I know, it's a bit naggy, but twice a season is over the top; regardless of price.



Let's also remember, yacht engines are very agricultural basic lumps, they run all day in dusty building sites or hot desert conditions when used as gennys or mixers/dumper trucks etc. I think there is a lot of fear generated about small putt-putt yacht engines on here, yes they can break, but when you consider the age of some yacht motors around our coasts, the reliability of engines that are abused through lack of any servicing is quite phenomenal... Just stick to the schedule and the engine will be fine, might stop more oil hitting landfill too. [/arrogant high 'n' mighty tree hugger rant]
 
[ QUOTE ]
... Ok I have a motorboat and this is a major expense hence my query. I'm thinking that with an average of 100 hours or less each season, then I am throwing away perfectly good oil? I stand ready to be contradicted.

[/ QUOTE ]

There is a way to tell:

Oil analysis monitoring. For anyone running big engines that need expensive oil, then I'd think it was a no-brainer.

A one-off oil analysis won't really tell you anything. What you need to do is get it done regularly. The lab will monitor trends in things like pH, viscosity, additive pack and contaminants, and actually *tell* you when to change the oil. It all sounds very expensive, but when last I looked it *wasn't* (admittedly about 10 years ago!). The company I knew was Wear Check (they are reasonably local to me) and it was £10-£20 per sample from memory. Incientally, their 'default' frequency for marine engines on their web site is monthy / 500 hours ( /forums/images/graemlins/grin.gif ). They way it worked was that they sent you a sampling kit (syringe & tube) and a mailer; you sucked some oil into the syringe, put it in the mailer and sent it back to them; they analysed it and sent you a report - phone call if there was anything unusual.

For exampe: Routine marine analysis

If it's costing you £50 a go to change the oil, then 2 samples a season is well worth it if you can go two, three, or more years between changes. In addition, you get advance notice of engine problems.

Serious suggestion - Talk to them: Wear Check

Andy
(No connection with Wear Check, but SWMBO once worked there as an analyst).
 
This months yachting monthly says it all about oil. Castrol also had it right when they called it liquid engineering. It washes, cools, cleans, lubricates, withstands high pressure and temperatures and combats the products of combustion, be it acid or particulates (it keeps them in suspension so the filter can take them out). One of the important factor for the oil is it's TBN number (total base number). This reduces with use and if you don't change the oil it will cease to nullify the acids produced in combustion. Also because the engine temp rarely gets that hot a lot of condensation can be produced which along with any fuel contamination will slowly dilute the oil making it less viscose and then the chain reaction begins.
Personally I change the oil and filter anually it's a lot cheaper than a new engine.
Rgds
Bob
 
Apart from preventive of engine wear, change oil will give you faster speed and much quiet run, especially on an aged engine.

I once had the boat went 1.5 knot faster after changed the oil.
 
The pollution caused by a worn engine is worse.
The energy to make a new engine or parts for it is way more than an extra 20 oil changes through its life.
The used oil is recycled.
There is no environmental case for not changing your oil frequently.
 
thanks for some interesting and informative inputs. I wasn't contemplating leaving oil changes for any great lengths of time but still think that maybe 200 hours spread over 2 seasons is still a reasonable life expectation for the oil. On hours alone you wouldn't contemplate a change until maybe 500 hours. The engines are 2 x perkins sabre 225ti which have an easy life.
 
[ QUOTE ]
One of the important factor for the oil is it's TBN number (total base number). This reduces with use and if you don't change the oil it will cease to nullify the acids produced in combustion. .
Rgds
Bob

[/ QUOTE ]
so therefore if the TBN only reduces with USE, i.e engine hours, and not the passage of time. I still don't think that stretching my 100 hours in one season to 200 hours in 2 seasons will result in me needing a new engine.
 
I can't speak for your engines but the recommended oil change period for my Yanmar is either 150 or 250 hours, depending upon whether you believe the owners' manual or the workshop manual. I change mine at 150 but if this occurs mid-season, which is often the case now that I am aboard for six months of the year, I change the oil but not the filter. 500 hours sounds like quite a lot to me.

I disagree with you that the oil does not deteriorate when the engine is not running. In boats there is a large change in temperature between normal operating and resting, which is basically the temperature of the sea. In the majority of cases the lower temperature will be below the dew point, so air drawn into the engine as it cools will be damp. Water will condense inside the engine and run down into the oil. If you leave this mixture over the winter the water will tend to dissolve the acid combustion products in the oil, leading to some corrosion. Although this is never going to corrode through any structural parts it can have a serious effect on critical components like piston rings, bores, cams and tappets. Modern bearings are unlikely to be affected.

An additional effect is that many oil additives do not like water, and having significant water present may adversely affect the oil's properties.

Your 'easy life' may also mitigate against oil life. Engine oils are designed to get hot, particularly the higher grade ones such as API CH and above. The chemistry of the oil does not operate correctly if running them cold. The oil is likely to remain basic at constant low temperatures, which can contribute to increased bore wear.

Considering the cost of the oil, weighed against the cost of your engines, stinting on oil changes is a false economy. It has often been argued that changing the oil more frequently than the recommendation is one of the best things that can be done to extend the life of an engine. Maybe not quite as much so as it was, given the life of modern oils, but worth bearing in mind if considering not changing it.
 
Re: When to change oil debate.

I would agree with most of the posts in that IF the oil has deteriorated you should, indeed must change it.

Where I disagree very strongly is the assumption that planned calander or hour based changes are the only way to ensure good oil quality, long life, low wear etc. I do not understand the logic written on here that is trying to convince me that my 21 year old yacht engine is worn and polluting as I do not change the oil every year. Sorry, but it starts in -5C easily does not produce either blue or dark exhaust, has full oil pressure and still produces the required power although the head has never been lifted ( Ford 1.6 XLD)

I avoid over 50k of costs annually in my day job by oil analysis of engines and some of these engines are over 20 years old. Condition maintenance and changing just before the oil goes out of specificaton limits is a far better way of avoiding cost to you, and reduce whole life cycle overall energy and planet resources as it is for all maintenance requirements. If you are using contaminated fuel in a dusty environment, not something I would expect in NW Europe, you may well change oil more frequently with condition rather than calender maintenance routines but that is the whole point.

Brian
 
[ QUOTE ]
Apart from preventive of engine wear, change oil will give you faster speed and much quiet run, especially on an aged engine.

I once had the boat went 1.5 knot faster after changed the oil.

[/ QUOTE ] I think you should have kept this post for April 1st !!
 
Sorry - 400 hours is the recommended interval on these , i.e 4 times the hours I do. 30 litres of oil is not cheap and having always changed it religously at the end of every season when it is still brownish ( as opposed to completely black) strikes me as wasteful. By "easy life" I mean one cold start a day with 6 or 7 hours of medium and a spell at wide open throttle each trip to work them. I take your points on acid/water contamination etc but I am still tempted to change it on alternate years.
 
[ QUOTE ]
.............The used oil is recycled..................

[/ QUOTE ]

Depends on who collects / empties the waste oil bin.

As to recycled oil - (reconstituted we call it) - it is cleaned, few anti-acid additives added, viscosity improvers, few detergent bases .... plus some other bits and bobs to make it pass spec for its' rating.

It then gets sold into the 'cheap-retail blend' market generally. In the economy blends - we take it that price indicates amount of virgin oil that is added to the recon oil. Pay more - get more virgins. /forums/images/graemlins/grin.gif
But it is not confirmed to us as many blenders do not wish to tell their secrets !

We test all oils including Lub's and for MY personal use ... this is NOT a market stand or reccommendation - it is how I look at it for my use : I buy economy mineral based oil from general car acc's shop. I do not buy fancy high priced as my engine is a vintage 4-107 and it's not worth it in my opinion. If anyone asks me - I say keep to oil change schedule if you use cheap recon oils as their 'body' is less durable (simple laymans terms ...). But of course my oil is now entering it's 3rd season .... OOP'S !! I'm thinking maybe give ol'Perky a b'day and change it !!
 
I agree this one is a stonker,

Perhaps everyone should think about there cars these engines get hotter, get colder, tend not to sit at constant revs unless stuck in traffic. long gone are the days of6 months or 6000 miles which ever comes first.

Oils have moved on a great deal over the years I for one will not be scare mongered into changing mine blindly following the throng I will however the best quality oil when i feel its time to change it and the filter is renewed everytime the oil is its only a small cost (£3.90) compared to the oil cost
 
<<< Perhaps everyone should think about there cars these engines get hotter, get colder, tend not to sit at constant revs unless stuck in traffic. long gone are the days of6 months or 6000 miles which ever comes first.

Oils have moved on a great deal over the years >>>

I think that's the point - it's certainly what I tried to convey with the YM article. Cars and driving have changed enormously over the past 20 years or so. Boats and their engines haven't, at least so far as the average yacht is concerned. Oils are developed for today's driving in today's cars, which means high revs, high temperatures, high power outputs. Yacht engines run slowly, cold, low power. They also run for long periods at constant revs, a difficult situation to lubricate. Very few manufacturers make oils for this kind of duty now - indeed, Shell dropped their Rimula C between me writing the article and YM printing it.

If you buy the 'best quality oil' for your yacht auxiliary engine you will certainly not be giving it the best treatment. And changing it 'when I feel it's time' sounds like a recipe for trouble - how and what are you going to measure?
 
Vyv, I am glad this has come up because it made me wonder when I read your article. Many boat engines are marinised car engines, eg Thornycrofts were BMC, now Mitsubishi. My Volvo M22 is a Perkins engine used in a Montego (yuk!)

So to think of car engines one way, and boat engines another is slightly confusing. Are you saying the above examples are older generation not suited to modern oils, as opposed to current engines, such as a VW TDi ?
 
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