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Hello long distance convoyers, And today's question is: Having installed 40 weight oil in my M37, and noticing a higher oil pressure even at idle, will I hurt, stress, or otherwise upset my engine with this oil?

Nope.

LIFER, That's encouiraging ! That means that i will finally get rid of a dozen or so quarts of 40 weight ....

I'll have to disagree with Lifer here. If it was a multi-grade oil such as 15-40, that's great. However a straight grade 40 does not circulate freely upon start up, the most critical time when most wear takes place. You mentioned higher oil pressure, that basically means the thicker oil is harder to pump, simply not good. Oil must be pumped into areas where the available path is only thousandths of an inch, the thick oil won't flow as needed in these critical areas as it should. If you are seeing these affects now in the heat of summer, winter time will be disasterous. You must understand oil pressure, some folks act like if they poured in 90 weight & it got the oil pressure to read normal in a worn out engine, they feel they have got a new overhaul. The truth is it's nothing more than a false sense of security, all they have accomplished is a fictitious reading. The engine wear will only speed up from here because of improper oil use & a lack of lubrication because of a restricted flow. Of course using 90 weight would be stupid, used that example just to make a point. If you intend to use a straight grade oil, 30 should be the max. Multi-grade oils of today are much better than straight grades. Don't know the condition of your engine, if it's not that great, it will get worse faster. If it is generally good now, it won't be for long on a diet of straight 40. Using recommended lubricants has a purpose. Many changes have taken place in oils since the M37's were new, thus better options are available today than the straight 30 the manuals suggest. Suggestions would be very different if the manuals were being printed today. Just because you have a supply of something on the shelf isn't a good reason to use it where it isn't recommended. I would search out another way to dispose of it I think.

Again, Charles makes a valid point! I didn't notice that you were on Long Island when I said "nope." It might be okay now, but it does get pretty cold up there in Noo Yawk in the winter. If what you have is a multi-grade, it should be okay. If it's straight 40 weight, it's better to sell it to someone else. My apologies!

Oh Oh ! Looks like I'm going to drain out that 40 weight ! Well, I can still use it to lube my winch amd choker cables, snatch block joints, and clevis couplings...But may I ask then, shall I use 10W30?

10W30 works just fine in the 230.
Gary

peter e mark wrote:Oh Oh ! Looks like I'm going to drain out that 40 weight ! Well, I can still use it to lube my winch amd choker cables, snatch block joints, and clevis couplings...But may I ask then, shall I use 10W30?

My personal recommendation is 15-40, such as Chevron Delo 400 multi-grade or Shell Rotella T. Even better is Royal Purple synthetic 15-40. These oils are fortified with strong additive packages to combat harmful by products of combustion like sulfuric acids, etc. The low # when the oil is cold is sufficient flow for cold starts, it gradually thickens with heat as the engine comes up to normal operating temp. We've used 15-40 for years in our rebuilds, great results.

Thanks Cal-Gary and Charles...You know, I do have a stash of 15-40 left over from my M35 spare parts bin....Maybe it will whistle like my old deuce !

peter e mark wrote:Thanks Cal-Gary and Charles...You know, I do have a stash of 15-40 left over from my M35 spare parts bin....Maybe it will whistle like my old deuce !

FYI - My engine ran noticeably better after I switched from 10W-30 to 15W-40.

If your engine has some wear (probably all of ours!) heavier oil can boost your oil pressure a bit, so I'm not surprised that you saw some positive results with the 15w40.

Some people go too far, such as during my Valvoline days when the kid in the new Honda that insisted on 20w50 racing oil in his 4 cylinder, then wondered why it coughed and chugged it's way out the exit door, around the building, then right back in the front door for the 5w30 that the manufacturer called for....
Gary

The recommendation for diesel oil is a good one. Any of these old motors need to have zinc in the oil for lubrication of the metal to metal parts. There is a lot of information on the internet on this subject. There were a lot of engines damaged when the oil companies took out the zinc for improved emissions. One of the last issues of Supply Line or MV has an aritcle on the subject with various oils listed with their zinc content.

MSeriesRebuild wrote:

peter e mark wrote:Oh Oh ! Looks like I'm going to drain out that 40 weight ! Well, I can still use it to lube my winch amd choker cables, snatch block joints, and clevis couplings...But may I ask then, shall I use 10W30?

My personal recommendation is 15-40, such as Chevron Delo 400 multi-grade or Shell Rotella T. Even better is Royal Purple synthetic 15-40. These oils are fortified with strong additive packages to combat harmful by products of combustion like sulfuric acids, etc. The low # when the oil is cold is sufficient flow for cold starts, it gradually thickens with heat as the engine comes up to normal operating temp. We've used 15-40 for years in our rebuilds, great results.

Charles,
From what I've learned from a petroleum engineer is that in the case of 15W-40, it is basically a 15 weight oil with viscosity improvers in it so that at 200 degrees instead of acting like 200 degree 15 weight oil it acts like 200 degree 40 weight oil. It doesn't thicken with heat it just does not thin out nearly as much as the straight 15 weight would. I just thought I'd pass along this tidbit I learned from my stint working in a hangar.

Greencom

greencom wrote:

MSeriesRebuild wrote:

peter e mark wrote:Oh Oh ! Looks like I'm going to drain out that 40 weight ! Well, I can still use it to lube my winch amd choker cables, snatch block joints, and clevis couplings...But may I ask then, shall I use 10W30?

My personal recommendation is 15-40, such as Chevron Delo 400 multi-grade or Shell Rotella T. Even better is Royal Purple synthetic 15-40. These oils are fortified with strong additive packages to combat harmful by products of combustion like sulfuric acids, etc. The low # when the oil is cold is sufficient flow for cold starts, it gradually thickens with heat as the engine comes up to normal operating temp. We've used 15-40 for years in our rebuilds, great results.

Charles,
From what I've learned from a petroleum engineer is that in the case of 15W-40, it is basically a 15 weight oil with viscosity improvers in it so that at 200 degrees instead of acting like 200 degree 15 weight oil it acts like 200 degree 40 weight oil. It doesn't thicken with heat it just does not thin out nearly as much as the straight 15 weight would. I just thought I'd pass along this tidbit I learned from my stint working in a hangar.

Greencom

I understand your explanation & know it is correct. My explanation was quick & quite honestly is the one most folks can relate too. If you get too technical, you blow a fuse with most people.

Yes, I have a tendency to drone on sometime. There are times when I explain something as I understand it only to find out I was wrong, then I learn something myself and I have learned many, many things on this forum.

Greencom