"Oil Pressure drop at idling"

[Chanquete]

Hello

I really dont know if I hava a problem.
My nearly new Volvo 2030 start immediately and run smoothly without problems.
But sometimes after sailing and motoring, during all day, with the warm engine, when I approach my mooring with the engine idling the oil pressure instrument indicate very low pressure.
I use excellent semisynthetic multigrade oil for diesel engines (Shell).
When I slightly speed up only a few rpm the pressure returns to normal.
I infere that a good approach would be to calibrate the engine slightly increasing the idling speed, for example to 800rpm or 850 rpm.
Perhaps other Volvo 2030 owners had similar problems.
I would thank very much any advice

 

[Tranona]

Can't help with low oil pressure as my 2030 does not have a gauge. Bit surprised you describe it as "nearly new" when it has been out of production since 2005! Not recommended to use semi synthetic oil. Recommendation is mineral oil to min CD spec, but usually CF 15/40 or 20/50.

 

[robmcg]

You need mineral oil not semi synthetic. It is becoming too thin when warm hence low oil pressure at tick over.

 

[Lakesailor]

Other than that, stop obsessing. If you've got good pressure under load you're OK.

 

[tillergirl]

And idle should be 850 + or - 25 rpm

 

[rogerboy]

+1

You need mineral oil not semi synthetic. It is becoming too thin when warm hence low oil pressure at tick over.

 

[VicS]

You need mineral oil not semi synthetic. It is becoming too thin when warm hence low oil pressure at tick over.

Why does whether it is a mineral oil, semi-synthetic oil or even fully synthetic oil have any bearing on it becoming too thin when warm? Surely that is down to its viscosity grade and that alone.

The correct grade is 15W/40 or 20W/50

 

[CAPTAIN FANTASTIC]

Why does whether it is a mineral oil, semi-synthetic oil or even fully synthetic oil have any bearing on it becoming too thin when warm? Surely that is down to its viscosity grade and that alone.

The correct grade is 15W/40 or 20W/50

Totally agree; and synthetic oils are much more stable than the mineral oils; I have a Volvo MD11C (40 years old ??) which run beautifully on full synthetic oil and I am aware that this sound like an anathema to many.

 

[CAPTAIN FANTASTIC]

Other than that, stop obsessing. If you've got good pressure under load you're OK.

+1; this is why idling the engine for too long is no good.

 

[vyv_cox]

The warning light switch is a mass produced device, cheaply made and with the inevitable variability of such things. I don't know the setting of yours but typically it might be intended to switch on at around 10 psi. But the range of actual values might be from 5 to 15 psi. If you really are concerned then try changing the switch but unless it lights when the engine is doing cruising revs, or the engine becomes particularly noisy, then I would not worry too much.

A good little test of the oil system is to take notice of how long it takes the oil light (and alarm) to come on when you turn the engine off. If it takes a second or two it is normal. With new oil it will usually take far longer, five seconds or so.

 

[LONG_KEELER]

Other than that, stop obsessing. If you've got good pressure under load you're OK.

I like engines that only have alarms and no instruments.

A humanoid nose, plus a few million years of human intuition takes care of the rest.

Ok. I'm just a skinflint.

 

[PabloPicasso]

+1; this is why idling the engine for too long is no good.

I've always been told to let diesel engines idle for awhile before stopping them?

 

[Chanquete]

Other than that, stop obsessing. If you've got good pressure under load you're OK.

Hy Lakesailor

Your answer tranquilizes me , its more the suggestion of a clever psychologist than the opinion of a sailor.
I sincerely agree with you.
Today I switched on my motor it runs softly 100%
I apologize.
Sometime boat owners like me are obsessed because perhaps we love to much our boats.

Chau

 

[neil_s]

My Bukh DV20 oil pressure warning light also comes on at idling speed when the motor is warm.

 

[Tony Cross]

Hy Lakesailor

Your answer tranquilizes me , its more the suggestion of a clever psychologist than the opinion of a sailor.
I sincerely agree with you.
Today I switched on my motor it runs softly 100%
I apologize.
Sometime boat owners like me are obsessed because perhaps we love to much our boats.

Chau

And some people (like me) just worry about stuff. If I didn't have anything to worry about I'd be really worried.

I sympathise Chanquete, I'm just the same, I'm always looking for something to worry about.....should I be worried about that?

 

[bert49uk]

Why does whether it is a mineral oil, semi-synthetic oil or even fully synthetic oil have any bearing on it becoming too thin when warm? Surely that is down to its viscosity grade and that alone.

The correct grade is 15W/40 or 20W/50

You would think so, but unfortunately you are wrong synthetic oils are made for modern engines with higher tolerances, synthetic oils are thinner and have a tendency to creep a bit like antifreeze they will always find somewhere to leak in older engines or older technology.
for over 25 years I have been working on Porsche cars and selling Porsche parts. Im the technical rep for PCGB and Porsche enthusiasts club. So many times People use Synthetic or Semi oils in old 911s (designed in the 50s) and ask me why the pressure has dropped and they have oil leaks, tell them to go back to mineral oil, no more problems. Ok in the modern models but no good in older models.

 

[Avocet]

The OP hasn't, I don't think, complained about the oil light being on? Wasn't it just an observation of low pressure on the gauge? If so, I wouldn't worry - ALL oils (synthetic or mineral) get thinner as they warm up and the pressure drops.

On a separate note, I'm intrigued as to why this should happen MORE in synthetic oil? I thought that being able to stay in grade" at higher temperatures was one of their main strengths?

 

[oldharry]

I've always been told to let diesel engines idle for awhile before stopping them?

Thats for turbo charged engines - i.e. most modern diesel cars. If the engine is switched off before the turbo has had time to run down, the oil supplyto the turbo bearings is cut off with risk of damage. One of the commonest causes of early turbo failure.

 

[VicS]

You would think so, but unfortunately you are wrong synthetic oils are made for modern engines with higher tolerances, synthetic oils are thinner and have a tendency to creep a bit like antifreeze they will always find somewhere to leak in older engines or older technology.

You say synthetic oils are thinner.
Maybe the lower viscosity oils tend to be the synthetic ones but are you telling me that a synthetic oil has a lower viscosity than a mineral oil of the same viscosity grade. ??

 

[robmcg]

But I think the size of the molecules in mineral oil is significantly larger than in synthetic oil which allows the synthetic oil to creep past seals that were not designed for that type of oil. Probably the description of 'thinner' is describing the ability of the oil to creep further rather than its absolute viscosity.