What oil grade?

[Lodesman]

My Westerbeke genny takes SAE 30/10W30; the manual says do not use higher viscosity oil. Did not anticipate being unable to find the proper grade oil in the Bahamas, but here I am. Not doing a full oil change; just keeping the beastie topped up, what's the best solution - add 10W40 oil for diesels; or SAE 30/10W30 for gas engines?

[Meggazombie]

Make sure to use disel oil if its a disel engine!
Do not mix synthetic and mineral oils, if you do not know the old oil, do total oil change!
To by some extra at the time for oil change aught to be good practice, then you got a safe oil to topp up with.
Only for topping upp a few % of the total volume, there is hardly any problems using a higher viscosity oil, the oil is almost certainly diluted with one or a few % disel.

[a64pilot]

The 10W-40 Diesel oil you speak of may be 15W-40.
If so I'd go with Shell Rotella 5W-40 Diesel full synthetic. It does cost a little more, but not that much more.
Any oil is better than no oil meaning if I had to I'd put almost any motor oil in as opposed to running below the add oil mark, But I don't like mixing even brands of oil if I can help it, probably foolish.

Straight 30W Diesel oil ought to be available almost anywhere, When the temp pretty much is always 80 F plus or minis ten degrees or so, is a multi-vis oil even warrantied?

Just re-read your not changing it, since you can't get the oil that is in it now, why not?


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[Stu Jackson]

Originally Posted by a64pilot

If so I'd go with Shell Rotella 5W-40 Diesel full synthetic.

What are your thoughts on synthetic vs dino?

[rwidman]

Originally Posted by Stu Jackson

What are your thoughts on synthetic vs dino?

My thoughts are, while synthetic might give you marginally better fuel mileage in a car and might extend the oil change interval, that wouldn't be the case in a boat or genset engine so it wouldn't be worth the extra money. I also wouldn't consider changing from conventional to synthetic in a high hours engine.

Other folks may have different opinions.

[Lodesman]

Originally Posted by a64pilot

Just re-read your not changing it, since you can't get the oil that is in it now, why not?

Got Rotella 10W30 in it. Had a quart or two spare when I left Florida; anticipated being able to find the correct grade in the Bahamas, but that has not been the case. My "top up" jug is almost empty, so I've been checking everywhere that sells oil in the Exumas, but all they carry is 40 or 10W40 (for diesels; there's more variety for gas engines). I don't actually care about mixing brands or adding syn with dino, if the label says they're compatible. AFAIK, many oils that are labeled 'synthetic' are really synthetically-made dino oil; they're better than conventional oils, because they are free of the impurities (waxes, esthers, etc) but are chemically identical to the dino stuff.

[glenn.225]

Lodesman

This link will tell you a good bit about oil specifications and it is written in plain english: Petroleum Quality Institute of America

Basically the four letters after the numbers state the specs for gas and diesel engines i.e. SAE 10W30 SF/CD, the SF rating is for gas engines and CD is for diesel.

So any oil with a C? spec is for diesels, higher the letter newer the spec.

[a64pilot]

Originally Posted by rwidman

Other folks may have different opinions.

I've never had issues with it, but haven't usually run Synthetic in Diesels due to cost and what I consider to be marginal payback. Almost without exception you change a Diesels oil because it's full of soot, not because of it breaking down or wearing out. A essentially low RPM Diesel especially a normally aspirated one really isn't hard on oil. and the extra protection afforded by Syn oil just isn't warrantied, maybe.
Take the extra money you spend on Syn oil and shorten your oil changes with regular oil and I'm sure you would be better off.
Having said that, I'm running Rotella full syn 5W-40 oil in my 27 yr old Yanmar 4-JHE with no issues, probably wasting money, but I've always tried to buy the best oil , the best filters etc, and do it myself, and I change oil every 50 hours or so when I'm not using it much, but will go 100 if I'm using it a lot.

Truthfully, I think a boat in the tropics may well be better off with a Premium grade straight 30W oil, multi viscosity oils do not last as long as straight weight oils, the viscosity improvers is the first to go in an oil, and the greater spread between the two numbers, the faster it breaks down.

This is where Syn oils can vary greatly from regular oils, a Syn oil may well act like a multi viscosity oil, without viscosity improvers, if I lived up in the great while North, no doubt I'd use Syn oil, but I want to live where a cold day is 60F and a hot day 90F, so regular straight weight oil makes the most sense there.

[sartorst]

People worry way to much about oil if its a diesel use a diesel oil!change it! if its new use what the manufacturer recommends when it starts to use more oil change to 30w when it gets really tired use 40w change it! Delo, Rotella , never a problem multi-viscosity in cold climates its rare to find an engine failure due to BAD oil most problems are due to being run low or out of oil , fuel dilution, water or not being changed, overheating, worry about those possibilities
I personally have had 2 gas engines start leaking oil after changing to a synthetic

[kas_1611]

Picking the collective grey matter here for a simple, plain English answer

Volvo recommend 15w/40 for engine and saildrive and for obvious reasons will not comment on use of any other grade. However, in Croatia, where I am based it is almost impossible to find 15w/40. The main oil here is 10w/40.

So the question is: "is it safe to use 10w/40 instead of 15w/40?"

Temperatures rarely drop below freezing (not that I'm using the engine in winter) and during the normal cruising season the sump is gently warmed by the 20ºC plus water of the Adriatic.

If it is perfectly OK to use 10w/40 in both the engine and saildrive it saves a heap of hassles, not to mention a few £ (or Croatian Kuna), as this grade of oil is available at every fuel station in 5 litre bottles instead of having to order in specially or in the rare event of find a 1litre bottle of 15w/40

Cheers

Keiron

[a64pilot]

RE 10W-40
I doubt it's Diesel oil, check the specs to be sure, but I bet it's spark ignition oil.
10W-40 is a very common car oil, never heard of a 10W-40 Diesel oil, but then of course I'm not in Croatia.

[Compass790]

I wouldnt sweat about 10w-40 if it has a C rating in it's SAE spec as stated in earlier post. Interesting article about motor oil testing here,Consumer Reports:Truth Motor Oils- July 1996 Although this was a while ago I imagine it still applies today. Most modern oils work in both petrol & diesel engines but I'd buy specific diesel oil if I could get it.
cheers Paul

[Vipe6]

SAE10W40 is a typical semi-synthetic (or synthetic based) oil. Can normally be used in engines that normally run on 15W40. Be sure to check the API classification and not use any oil with an API lower than the manufacturer of the engine reccomends.

[a64pilot]

Originally Posted by Compass790

Most modern oils work in both petrol & diesel engines but I'd buy specific diesel oil if I could get it.
cheers Paul

I'll disagree a little, it may seem like semantics, but I don't mean it to be.
While it is true that most Diesel oils are acceptable in spark ignition engines, the flip side of that is not true, Diesel oils are usually a little overkill for spark ignitions engines, and there are some additives in some that may not be good for catalytic converters and O2 sensors, they won't damage the engine.
Most spark ignition oils won't meet Diesel standards, which ones I don't know enough to be specific, but be real sure the oil you buy does meet the min Diesel standard your engine calls for.
I'd stick with your second sentence, I make sure I can get it by always having at least one change worth of oil on board. I leaned this after a massive oil leak from an external filter, all I had on board was used oil, which worked fine of course, just I hate pouring used oil in my engine.

[Crew of Turning]

There is a very good write-up on diesel oil (dino ) done by Cox Engineering in the UK. It is worth a read. Myself, I drifted away from the hard specs put forward by the engine manufacturers' oil grades some time back. I use Shell Rotella 15-40 in 3 different engines without any problems. My yanmar 2qm20 (1978) on the boat, also a 1980 (ish) snowblower and a 2005 Honda lawnmower. All 3 of these engines function in completely different seasons and demands.The land based engines are both air cooled and completely different designs. The blower is a old f head and the mower is a newer ohv. All of them run well. Just my opinion, change it (oil) within reasonable time frames. I do all 3 at the end of their seasons. The 2qm always less than 200hours per summer.