Optimum Oil Level ?

narcer

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What is the optimum engine oil level in relation to the guide on the dipstick ? Bearing in mind that the dipstick markings are absolute "minimum" and "maximum", normally (depending on the size and volume of the sump) with a marked field in between of upto a few centimeters. Seems like an obvious question, but I was recently told by an engineer that filling it upto the max level is not necessarily the best option, but better is to leave it one notch down from the max.
 

RichardS

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What is the optimum engine oil level in relation to the guide on the dipstick ? Bearing in mind that the dipstick markings are absolute "minimum" and "maximum", normally (depending on the size and volume of the sump) with a marked field in between of upto a few centimeters. Seems like an obvious question, but I was recently told by an engineer that filling it upto the max level is not necessarily the best option, but better is to leave it one notch down from the max.

It's not that important as even on the full mark some margin for over-filling will have been allowed for.

Once the engine is running the level drops anyway as the oilways and cylinder head get their share.

I prefer to fill to the top mark as it make checking whether any oil has been used a bit easier.

Richard
 

Avocet

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I've always gone for the maximum (boat and cars). Current car handbook certainly tells me to top it up to the "maximum". It's hard to see what could be bad about having more oil in the system to dissipate heat. OK, over-filling is bad for a variety of reasons but I think the "max" mark should actually say "optimum".
 

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The one issue with the advice above, which is sound, is that engine manufacturers have no control over the angle of installation of a boat engine. Depending on that angle, and the precise fore-and-aft position in the sump which the dip-stick measures, some compensation in 'optimum' reading may be warranted.
 
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PaulMcC

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The one issue with the advice above, which is sound, is that engine manufacturers have no control over the angle of installation of a boat engine. Depending on that angle, and the precise fore-and-aft position in the sump which the dip-stick measures, some compensation in 'optimum' reading may may be warranted.

I asked the Beta Marine guys exactly this question at the boat show last year. To be honest the guys I spoke to were not super-techy (no overalls) but their recommendation was to fill to just above the middle of the range. I now go two thirds of the way from min to max.
 

GrahamM376

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The one issue with the advice above, which is sound, is that engine manufacturers have no control over the angle of installation of a boat engine. Depending on that angle, and the precise fore-and-aft position in the sump which the dip-stick measures, some compensation in 'optimum' reading may be warranted.

When I installed my new engine the instructions were to fill with a stated amount of oil and then mark the dip stick.
 

Lon nan Gruagach

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An uncertain amount less than minimum and you start to run dry, the oil warning light should pre-empt any damage.
An uncertain amount more than maximum and you will probably first start spilling oil and just possibly if you really over do it cause something nasty to happen in the crank case.
 

macd

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The max mark is there for a reason - that's how much you fill it.

The 'max' mark is typically established for an engine installed horizontally. In extreme cases...engine at a considerable angle, dipstick very much to one end or other of the sump...the marks will give readings quite different from those the manufacturer intended.
That said, the issue is rarely critical: the difference between the high and low points on the dipstick is itself quite considerable, as is the latitude for filling. However, anyone with an engine with the extremes mentioned in the first pragraph might reasonably take this into account.
 

narcer

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An uncertain amount less than minimum and you start to run dry, the oil warning light should pre-empt any damage.
An uncertain amount more than maximum and you will probably first start spilling oil and just possibly if you really over do it cause something nasty to happen in the crank case.

I'm no expert but I've heard on record that an overfill, especially in relation to healing angle can result in the main crankshaft/ bearings "beating" the surface of the oil and causing frothing. This obviously reduces lubrication and also the life span of your engine.
 

Aja

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Always fill the amount of oil stated in the handbook. In my case 5.9 litres. Angle of engine makes a huge difference. Don't always rely on the mark on the dipstick. It may be a standard mark for when the engine is absolutely level

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Donald
 

Skylark

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The dip stick min mark is the minimum oil capacity for optimum lubrication. The max mark is the maximum oil capacity for optimum lubrication.

When Noah was a boy, oil levels remained fairly constant because loss of oil burned was closely matched by unburned fuel entering the oil system. By the time an oil change was due, the content of the sump contained a lot of fuel.

Over filling can cause a lot of damage, if conditions conspire against you. There are recorded cases of engine seizure due to hydraulic locking of certain components (thrust bearings iirc). If the rotating crank churns the sump oil it can overheat, froth and lubrication can be lost. This is often more relevant to gearboxes.
 

KellysEye

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>The 'max' mark is typically established for an engine installed horizontally. In extreme cases...engine at a considerable angle, dipstick very much to one end or other of the sump...the marks will give readings quite different from those the manufacturer intended.

Having sailed boats of 25 feet, 32 feet, 38 feet, 40 feet, 48 feet and 52 feet including two American brands and three European brands, plus the steel boat we owned, I have never seen an engine that isn't horizontal. No company would install and engine that isn't horizontal for obvious reasons.
 

macd

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Having sailed boats of 25 feet, 32 feet, 38 feet, 40 feet, 48 feet and 52 feet including two American brands and three European brands, plus the steel boat we owned, I have never seen an engine that isn't horizontal. No company would install and engine that isn't horizontal for obvious reasons.

Are you being deliberately obtuse? The angle in question is of the crankshaft, not lateral. Most yacht engines installed with conventional prop shafts are NOT horizontal. Look in any yard.
Any supplier of marine engines will specify the maximum angle of installation. In the case of mine, it's 15 degrees either way from horizontal. Mine happens to run at 9 degrees.

I'd be very interested to learn what your "obvious reasons" are, because they're certainly not obvious to me.

Incidentally, the installation instructions go on to say that "when our engines are installed at varying angles of inclination, the normal markings of the dipstick should be disregarded. It is probably better to drain the lubricating oil from the sump...then add the recommended amount of lubricating oil - noting it's position on the dipstick - then marking the dipstick."
 
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jwilson

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>The 'max' mark is typically established for an engine installed horizontally. In extreme cases...engine at a considerable angle, dipstick very much to one end or other of the sump...the marks will give readings quite different from those the manufacturer intended.

Having sailed boats of 25 feet, 32 feet, 38 feet, 40 feet, 48 feet and 52 feet including two American brands and three European brands, plus the steel boat we owned, I have never seen an engine that isn't horizontal. No company would install and engine that isn't horizontal for obvious reasons.

There ARE yachts with engine mounted horizontally, but they are in a minority, often modern flat-hulled boats with saildrives, or older designs with hydraulic drives. Almost every traditional shaft-drive installation has the engine angled at maybe 10 degrees down at the aft end.
 

lw395

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>The 'max' mark is typically established for an engine installed horizontally. In extreme cases...engine at a considerable angle, dipstick very much to one end or other of the sump...the marks will give readings quite different from those the manufacturer intended.

Having sailed boats of 25 feet, 32 feet, 38 feet, 40 feet, 48 feet and 52 feet including two American brands and three European brands, plus the steel boat we owned, I have never seen an engine that isn't horizontal. No company would install and engine that isn't horizontal for obvious reasons.

Not seen that many yacht engines then.
Most yachts without saildrives have the engine sloping.
 

lw395

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Unless the dip stick is at one end of an inclined engine I would go for the middle.
Too much oil can cause real problems, frothing, or worse still drowning the bores causing the engine to run on its lube oil, which can be destructive.
But you normally need to put a lot of extra oil into a yacht engine to make any difference.

At least boats float roughly level, my car reads different depending where on the drive I park it.....
 

MM5AHO

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I have a Volvo MD2030.
I asked a Volvo marine engineer once, he advised to fill to half way on the dipstick, and to never fill above that. Given boats heel angle he said that model doesn't like too high an oil level.
If I add the handbook volume of oil, it fills way above the dipstick max line.
 
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