Oil in the Med

[Renegade_Master]

Someone recommended when changeing my oil that its best to us 20/50 instead of the usual 15/40 cos of higher running temperatures in the Med. Does the panel agree?

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[tcm]

um. Isn't the engine runing temperature a lot higher than the ambient air temperature, and anyway controlled by a thermostat? So, the engine doesn't run hotter, though it might be hotter in the engineroom which has no thermostat, unless you have blowers on a thermostat too. So I bet it would make hardly any difference, and certainly not make back the cost of the oil change.

However, I hear good things about using synthetic oil, saving fuel and so on. But not tried it.


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[DavidJ]

Agree with tcm. Also it's the specification from Volvo and they probably have more engines in the Med than anywhere else.
I don't bother using Volvo oil (and probably nor does the guy who does your service) I really don't believe that they add any significant additive to prolong engine life.
David

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[tr7v8]

When I saw the subject line I thought you were on about the tanker that sank last year, thought you'd had too much sun on the head.

Oil viscosity in engines is predominately dictated by two things. The running clearances in bearings and the like and also drag when starting.
Modern engines run much tighter bearing clearances and therefore can afford to run lower viscosity oils and keep sensible oil pressures. The thinner oil has various other benefits, such as lower drag when starting (smaller battery and starter), lower pumping losses from the oil pump and therefore better fuel consumption.
Modern engines also tend to run hydraulic tappets to reduce maintenance costs (no tappets to adjust) although as far as I know boat engine manufacturers haven't grasped this yet! Hydraulic tappets hate thick oil with a notable exception of the Rover V8s, which also runs very low oil pressure to boot.

As TCM said engine temp is dictated by the cooling circuit and in this sense boats are much better off than cars in having a virtually unlimited quantity of seawater for cooling, also most running tends to be at reasonably high revs thereby ensuring steady internal temps rather than a car which tends to be stop start type short journey's.

I am personally never convinced about synthetics especially for diesels, temperatures in diesels are much lower so therefore oil frying and causing carbon deposits in the turbo bearings is less likely which is the main reason for running synthetics.
What diesels do suffer from is blowby which cause the oil to go black very quick, far better to spend the money you'd have spent on synthetics on mineral oil changed more often!
Disagree? Synthetic useage was common with early turbo road cars where they died fairly rapidly if you ran mineral, but the average Volvo truck does 250K miles before they think about overhauls, stop start using air as a cooling medium which varies in temperature far more than sea water doesAND does it all on standard mineral oil!

<hr width=100% size=1>Jim

Draco 2500