iainbluk
Member
Average speeds for a car used on motorways is more like 43mph, which would make a 12000 mile service requirement 280 hrs. Cars used more on a roads and town would have considerably lower average speeds.
How many hours do you change your oil?
- Thread starter tom_sail
- Start date
Average speeds for a car used on motorways is more like 43mph, which would make a 12000 mile service requirement 280 hrs. Cars used more on a roads and town would have considerably lower average speeds.
brianhumber
New member
You should only change oil when it needs it.
Have a 1987 engine over 5,000 hours and the oil changes work out at around once per 5 years.
How do I know when to change?- I have the oil analysed, this simiply being an extension of of land and marine commercial practice for decades.
Yes when fuels had higher sulphur content than now the base tended to decrease faster but I have noticed nowadays with low sulphur fuels, its the water content that creeps up faster. I have never had to change the oil in this engine due to contamination, excess suspended solids etc.
However the practical answer is change to when you are happy to change it. Most will change far more frequently than is needed but feel confident and happy they have done so even though they have not achieved anything in terms of extended engine life or reliability by doing so.
The saddest thing about this subject are all those 'authors' still peddling advice in magazines and books about topics they have no actual technical background in.
Brian
Have a 1987 engine over 5,000 hours and the oil changes work out at around once per 5 years.
How do I know when to change?- I have the oil analysed, this simiply being an extension of of land and marine commercial practice for decades.
Yes when fuels had higher sulphur content than now the base tended to decrease faster but I have noticed nowadays with low sulphur fuels, its the water content that creeps up faster. I have never had to change the oil in this engine due to contamination, excess suspended solids etc.
However the practical answer is change to when you are happy to change it. Most will change far more frequently than is needed but feel confident and happy they have done so even though they have not achieved anything in terms of extended engine life or reliability by doing so.
The saddest thing about this subject are all those 'authors' still peddling advice in magazines and books about topics they have no actual technical background in.
Brian
D
Deleted member 36384
Guest
A very interesting point Brian. I have often wondered about analysis but thought it would be too expensive for the volume of oils that I would be replacing on the yacht. However, if one is getting 5 years out of oil then it may start to be economical. A caveat - I don't know how much the analysis service would cost, but assume around £100. I used to have analysis carried out on large engines and pumps on drilling rigs for this very same reason. There was 1000s of litres involved so it was economical.
E.T.
New member
I dont profess to be an expett. Nor am i experienced with marine engines, however, i did a lot of research into oils and change intervals for motorbikes.
There is two main things that make oil deteriate (okay more, but two main considerations):
1 what the oil is doing. . . In race engines which tend to be loaded and spinning at high rpm ( also on bikes this same oil is in the gearbox and lubricating the clutch plates if it is a wet clutch) this has the effect of breaking the polymer chains down. Fully synthetic oils have longer chains than mineral oils and they are slippery and last longer than minerals. These arent used on bikes because of clutch slip. But they are in car engines and hence the long oil change intervals that can be obtained with most modern cars. Bikes the typically have changes at 4-6000 miles (4k is most common)
Marine engines of the type we are talking about here are unlikely to be run at 12000rpm
nor run through a gear box. Deteriation from polymer breakdown is likely to be very low.
2 what is subjected to in terms of moisture. This will be the killer for marine. Some cars like Mercs and BMW have a moisture sensor for the engine oil. If youre like me and do long extended journeys where the oil heats up properly and all water is dried out, the service interval will be far longer than if i did a local jouney of a couple of miles every day. So rather than a service interval of x miles, it is actually determing what state the oil is in, by measuring humidity.
With marine engines then, in reality a lot has to do with how long they run in a single go each time. If you motor for a long period each time the oil deteriation will be far far less than a 5 min lets get this thing off the pontoon type use. This is the thing that should most effect frequency of change.
Manufacturers will tend to urge on the cautious (quite right too. So i would say follow what they say in terms of hours, or once a year whichever is sooner. If you know the engine has had lots of 2 minute runs, then i would err on the cautious and make an extra change jic. . . Oil is cheaper than engines, as someone above has already said.
There is two main things that make oil deteriate (okay more, but two main considerations):
1 what the oil is doing. . . In race engines which tend to be loaded and spinning at high rpm ( also on bikes this same oil is in the gearbox and lubricating the clutch plates if it is a wet clutch) this has the effect of breaking the polymer chains down. Fully synthetic oils have longer chains than mineral oils and they are slippery and last longer than minerals. These arent used on bikes because of clutch slip. But they are in car engines and hence the long oil change intervals that can be obtained with most modern cars. Bikes the typically have changes at 4-6000 miles (4k is most common)
Marine engines of the type we are talking about here are unlikely to be run at 12000rpm
nor run through a gear box. Deteriation from polymer breakdown is likely to be very low.2 what is subjected to in terms of moisture. This will be the killer for marine. Some cars like Mercs and BMW have a moisture sensor for the engine oil. If youre like me and do long extended journeys where the oil heats up properly and all water is dried out, the service interval will be far longer than if i did a local jouney of a couple of miles every day. So rather than a service interval of x miles, it is actually determing what state the oil is in, by measuring humidity.
With marine engines then, in reality a lot has to do with how long they run in a single go each time. If you motor for a long period each time the oil deteriation will be far far less than a 5 min lets get this thing off the pontoon type use. This is the thing that should most effect frequency of change.
Manufacturers will tend to urge on the cautious (quite right too. So i would say follow what they say in terms of hours, or once a year whichever is sooner. If you know the engine has had lots of 2 minute runs, then i would err on the cautious and make an extra change jic. . . Oil is cheaper than engines, as someone above has already said.
vyv_cox
Well-known member
There is almost no comparison between a modern high-tech automotive oil and the grades that most marine engine manufacturers call for. Current best grades are synthetic, which means they contain no distilled oil, but instead use oils synthesised from gases and light solvents. This helps to prevent fouling by long chain hydrocarbons. the biggest difference though is that the additive package is about 20% of the total content. It contains many different additives, such as antioxidants, viscosity improvers, anticorrosion, boundary lubricants, detergents, etc., all designed to extend the life of the oil, and to avoid topups, as far as possible.
By contrast, API CD, called for by most current engine manufacturers, even though it has been obsolete for years, contains almost no additives whatsoever. There is lots more on this subject, and the need for low grade lubricants in yacht engines, on my website.
So to answer the OP, change oil at least once per season, as it has almost no capability to combat corrosion that is inevitable in a cold-running engine. I change mine twice per season but I live aboard for half the year.
tom_sail
New member
Thanks for the replys! A wide range of views, very helpful!
Leif-J
Member
Brian, where do you get this analysis done and what is the cost?
As I understand it you can learn a lot about the condition of your precious machine from such an analysis, so it might be woth considering even if I choose to change oil anyway.
Brgds
Leif