30wt oil vs 15-40 wt

The recommended oil for my 1979 Lehman 120s is 30 wt. The PO was using 15-40. I know multi weight oil wasn't generally used in 1979 but is their any reason to use 15-40 rather than 30 wt? What are others using in their lehmans?

Multi grade oil has come a long ways. When it first came out, maybe 30 or so years ago it was made with a rubber compound, yes rubber (well elastomer actually) that gave it its multigrade properties but lacked lubricity. Engine manufacturers knew this and smart ones didn't approve it for use in their engines.

But today much has changed and the lubricity is good. And for some of the synthetic versions it is better than dino oil stock based single grade oils.

I can't think of any reason not to use it today in any engine.

David

There's been so many Lehman owners that have used 15W40 for so long I think it's safe to say it's OK to use and some think it's better depending on your temp ranges.

I use it without reservation.

Again....at one time watch manuals said to use only whale oil....guess where we are now.

There is no reason not to use 30 or 40w over 15-40. But then there is no real reason not to use 15-40 instead of 30 or 40w either IMO.

I leave NJ in December. Last December when I left Baltimore Harbor I had to break ice to get out of the marina and almost didn't make it. It was 15 degrees that night.

!5W40 makes for much quicker starts in weather like that if the battery is weak at all.

Granted some say their Lehman spins fine with 30Wt at those temps...great...I use 15W40 and like that it's easier on everything when starting and I don't feel the need for an 8D starting battery when a Group 27 or slightly larger does just fine.

Blackstone oil analysis says everything is just dandy.

Thanks. I couldn't think of a reason, I used multi weight in my old perkins and it wasn't that much newer than these. While I'm at it, any preference in oil filters? PH8A, WIX 51515, NAPA 1515? All the same?

I've used both on my FL 120 . Just got back my blackstone report with 130+ hrs since last change as I'm doing the loop. Best report ever and thats with 6500 hrs. Too many people spend too much time worring about inconsequential matters.

FF says the additive package in multi-vis oils is 30% of what's in the can. Oil is probably the only thing in the can that actually lubricates. When you need MV oils I say buy then .. Like for your car or truck. We start them frequently when very cold and drive them almost immediately .. Sometimes on the highway. Almost everybody keeps their engine compartment warm enough on their boat so starting in cold weather is absolutely no problem unless there's something wrong w your engine. Under normal conditions you absolutely don't need MV oil at all. So get 30 wt oil that has the best lubricating abilities or 40 wt in hot weather. We use the best paint for the application in mind and we should use the best oil.

When I worked in a diesel electric power house we had a 300 gal dry sump oil tank. It took 24hrs to heat the oil and coolant. All that time both were being circulated throughout the engine heating the engine. The oil we used was 30W RPM Dello. The chief engineer could have specified 10W-30 but he knew he did'nt need it and he knew straight wt oil was better.

We should be using 30 wt for the same reasons.

I'm not saying MV oil is going to hurt your engine even if your old engine manual specs it. I do think wide ranging non-synthetic MV oils like 5W-30 should be avoided as lots more viscosity improves are added to achieve that MV rating. Either 10W-30 or 15W-40 will be fine .... But straight wt oil is a little bit better.

One should realize that 10-30 oil is not 30wt oil that has been doctored to perform like 10wt oil when cold. It's just the opposite. 10-30 oil is 10 wt oil doctored to behave (viscosity wise) like 30wt oil when hot. So 10W-30 oil is actually 10wt oil ... Modified.

meridian is absolutely correct. But if you want to talk about it or use oil that is slightly better use straight wt oil.

I use NAPA filters for the most part. I stay away from Fram filters.

Where is FF?

Not sure Spy but you can be sure there's no internet access. About twice a year he goes MIA for a couple weeks. Probably cruising the ditch and dodging roomarans with oxygen tents.