Engine Oil level , what is best practice

[Momac]

Should the oil always be filled to the high mark on the dipstick or is it better to have it a little under the high mark on a cold engine ?
After all it would be way above the low mark.

Just thinking slightly under filling might be better than over filling .

 

[Mr Googler]

Should the oil always be filled to the high mark on the dipstick or is it better to have it a little under the high mark on a cold engine ?
After all it would be way above the low mark.

Just thinking slightly under filling might be better than over filling .

I fill half way on the dip....makes me keep a closer eye on it if nothing else

 

[Old Harry]

it would depend on engine "down angle" the ds would surely be marked for engine installed horizontally

 

[Momac]

it would depend on engine "down angle" the ds would surely be marked for engine installed horizontally

Let's say the engine is level.

 

[Portofino]

Just put the correct accurate amount in next service and go from there dip stick wise .

 

[Boat2016]

What is it at when your engine has been serviced ?

 

[Momac]

What is it at when your engine has been serviced ?

I have filled it to the high mark previously ,as have the professionals in the past.
I have never needed to top up between services.
Just wondering what others do.

 

[Boat2016]

I have filled it to the high mark previously ,as have the professionals in the past.
I have never needed to top up between services.
Just wondering what others do.

Then if it were me I would stick with the same as long as you trust the professional you have been using.

 

[TheOrs]

Just wondering what others do.

I always fill (boats, cars, lawnmower etc.) to the high level. Gives maximum leeway + let's you easily see if you are using/losing oil.

 

[MapisM]

it would depend on engine "down angle" the ds would surely be marked for engine installed horizontally

NOOOO!
The DS doesn't come already marked from the manufacturers, with marine engines.
The MIN/MAX marks are stamped on it after the engine installation, upon commissioning.

In answer to OP question, I fill to max level upon oil change, but I don't add any afterwards, unless it goes down to half way between min and max.
Which actually never happened with any of my boats, also in seasons when I made a lot of hours.

 

[Assassin]

Mapis

You have to run your engines to use any oil.

 

[Assassin]

Best practise is to fill your engine to the full mark on the dipstick and keep it close to, or on this mark as it is there for a reason.

As soon as you start your engine your level will drop as it primes the engine and as boats often stand for long periods between starts it may rise slightly above the top mark if the engine is standing for a long period.

 

[john_morris_uk]

Does it really matter?

Apart from knowing whether the engine is using oil (a useful thing) so long as the oil level is maintained within the limits of max and min who cares?

 

[Portofino]

Does it really matter?

Apart from knowing whether the engine is using oil (a useful thing) so long as the oil level is maintained within the limits of max and min who cares?

That’s what I was thinking .
Most manufacturers and service guys fill 1/2 way between the two marks .
Some cars have a hatched area occupying say ( on a scale 1-10 the area between 4 and 6 .

Personally I go for exactly 1/2 way because overfilling is damaging too .Too high initial crank case pressure at cold start while its warming and being distributed.
There’s a crank bearing on the end of the crank where the pulley / drive plate fits , this has a seal and I don’t wanna blow that .
Also with marine there’s potential for other fluids like water via leaky oil coolers getting in or just plane fuel from weepy rings ,and the level of now mixed fluids increasing .
I think you would spot that sooner if been 1/2 way for ages then starts to rise .
Where as if it’s on or above the top mark , it just risers more and I suspect there more chance of it being missed ?

 

[Tamar]

My Perkins seems to be happy on the 3/4 mark. I used to worry about where the other 1/4 was going but it's stays there. As long as you have oil on the dipstick. But leaving it too low might leave the engine vulnerable in rough seas.

 

[spannerman]

NOOOO!
The DS doesn't come already marked from the manufacturers, with marine engines.
The MIN/MAX marks are stamped on it after the engine installation, upon commissioning.

In answer to OP question, I fill to max level upon oil change, but I don't add any afterwards, unless it goes down to half way between min and max.
Which actually never happened with any of my boats, also in seasons when I made a lot of hours.

Nooooooo, every single Volvo from small sailboat engines all the way through 4-6 cyl, V6/8 and up to D 12 ‘s, also Yanmars and Mercruiser from 130hp up to 1200hp supercharged bigblock V8’s that I have installed ALL had marks on the dipstick from the factory. Some installation manuals advise different oil quantities on shaft drive installations if the engine exceeds a certain angle, but that is rare as usually an angled output on the gearbox is used to compensate.

 

[MapisM]

Well, I take your word for it.
Fwiw, I was told what I previously said by Cat, MAN and MTU official dealers - and all of them were referring to shaft installations.
If my generalization is wrong I apologise, but I surely struggle to see the logic of factory marking.

I mean, even with outdrive powered boats, where engines are always horizontal, the position at rest can be VERY different, depending on the hull where they are installed: very fast and narrow boats typically sit in the water MUCH lower astern, compared to more sedate cruisers.
If there is any logic in marking the dipstick at the factory, I can't for the life of me understand what it is.
Maybe those manufacturers consider the approximation acceptable, but an approximation it has to be for good, I reckon.

 

[Momac]

Well, I take your word for it.
Fwiw, I was told what I previously said by Cat, MAN and MTU official dealers - and all of them were referring to shaft installations.
If my generalization is wrong I apologise, but I surely struggle to see the logic of factory marking.

I mean, even with outdrive powered boats, where engines are always horizontal, the position at rest can be VERY different, depending on the hull where they are installed: very fast and narrow boats typically sit in the water MUCH lower astern, compared to more sedate cruisers.
If there is any logic in marking the dipstick at the factory, I can't for the life of me understand what it is.
Maybe those manufacturers consider the approximation acceptable, but an approximation it has to be for good, I reckon.

I am sure the boat and therefore the engines are at a different angle at 20 knots compared to 0 knots. I imagine with sterndrives the engine angle for any given engine and drive assembly is pretty much the same in every boat so the outdrive sits correctly in the water.

Having just changed the oil and run the engines 5 minutes I immediately checked after stopping them and the oil is about 3/4 of the way between the low and high marks on the dipstick (both engines) If I leave the engines 24hrs the oil will be on the high mark.

I will not be checking the oil level at 20 knots.

 

[john_morris_uk]

I will not be checking the oil level at 20 knots.

I think you might be wearing it if you did!

 

[MapisM]

I imagine with sterndrives the engine angle for any given engine and drive assembly is pretty much the same in every boat so the outdrive sits correctly in the water.

Yep, but there are other factors.
As I tried to explain, the static AoA of fast speedboats (with big and heavy engines placed inside narrow, deep-vee hulls) is much higher than in any cruiser, even if the engine+drive assembly is installed exactly in the same way (X-dim aside, but it's irrelevant in this context).

The dynamic AoA is obviously another kettle of fish, but has bugger all to see with dipstick marks.
Frankly speaking, it takes a remarkable imagination to read my previous comment ("the position at rest can be VERY different"), as a suggestion to measure the oil level while cruising at 20kts...