synthetic oil

[jim rosenthal]

Would someone explain to me why marine engines are not supposed to use synthetic oil? Cummins says not to use it, Tony Athens says not to use it, etc. I can't figure this out when so many new high-performance engines in cars and trucks have synthetic oil as factory fills. And I think some of them are diesels. I'm curious if anyone knows the answer.

 

[rsmith]

I've been using Lubrication Engineers Monolec GFS 40 in the 12/71's for over 30 years and almost 10,000 hours.

 

[krush]

Possibly because they are scared to say it is ok. Put yourself in their shoes...they haven't done extensive 1000000000000000 hour testing with synthetics....and synthetics may be fine, but they don't want to put their approval on it and have people come back to them if there are some failures that may or MAY NOT be related to the synthetic oil.

I know there are quite a few synthetic diesel oils out there and that many truck fleets have been using them for years. Combined with bypass filtration and oil analysis, owners have been able to extend oil changes greatly.

 

[jim rosenthal]

That's kind of what I thought. I can't imagine truck fleet use is much easier on diesels than marine use- maybe marine use is worse, in a way, since the engines sit for weeks and then have to go out, get warmed up, and work hard.

I'm not going to make any changes- I'll still be filling the engines up with Rotella when I do the annual oil change. But if they ever approve it, I will try synthetics and I'll bet they run just as well, and use less fuel. Not enough to pay for the difference, but less.

 

[MikeP]

FWIW, DD said 15W40 syn was ok somewhere in the late 70's/early 80's. The DD engine manual that came with our 1980 53MY as part of it's original documentation states that. However, sometime between then and the 90's, DD changed back to recommending straight weight oil non-syn oil. The latest info that I know of, a 2005 bulletin re oils, states straight 40 or straight 50 (depending on application/temp) CF2. There is no mention of syns or multiweight.

Obviously there must have been some reason they abandon their recommendation for a syn multiweight and went back to non-syn single weight. But I have no idea what that reason was.

I agree that it seems odd, especially since auto engines have gone the other way, even for older engines. Ferrari, for example, issued a bulletin 15 years ago calling for 5W40 syn in ALL their v8 engines regardless of year (dating back to mid 70s when 20W50 was the owner's manual recommendation.) 0W40 syn is a common fill nowadays.

And modern engine research has demonstrated that something like 0W40 syn is better in every way for an engine - it gets where it needs to go much faster when the engine is cold and the viscosity hot is the same as the 40 wt straight. Some racing engines nowadays use 0wt oil...

 

[Trojan]

It may be the fact Detroit's are old 2 stroke diesel engines. Synthetics have a different viscosity and there rating of break down under heat and pressure are different. The synthetics that I have used seem to be a lot thinner viscosity than oil. I know the surface friction is far less than oil. This is the good part. But with the OLD lead babit bearings the tolerances on the radial fit is quite large. Requiring the thicker oil. And with the large fit there may be to much wash by with synthetics. With the higher compression of the diesel and the thinner viscosity of the synthetics the babit bearings won't hold up. The oil acts like a cushion between the two rotating parts. The newer engines don't use babit bearings. They are a cintered type bearings and bushings. The radial fit is smaller. The material is harder and the heat tolerances are greater.

BILL

 

[MikeP]

Bill, I suspect you are right; the tolerances involved are probably the issue. But syn 0W40, for example, is the same viscosity hot as straight 40 so my suspicion is that the "problem" is that at lower temps, before the engines are warmed up, there is insufficient oil flow of the lighter weight (at that temp) oil to handle the clearances involved. It would seem to me that a higher volume oil pump would take care of that but perhaps it's just not a practical solution and one that probably doesn't matter anyway - why bother if the "old" oils work fine for the job.

For engines like mine, which never get much over 165 degrees at displacement cruise, I suspect that a multiweight never gets hot enough to be at its "full" weight. And since DDs are known to be operated at long periods at idle/low speeds (even though DD does not recommend idling for extended periods) I'm thinking that's the reason multi weights are not appropriate.

But that's just speculation on my part - I'm no oil expert though I have read an awful lot of material regarding modern syn oils and their characteristics. Their multiweight properties are essentially the opposite of dino oils which makes syns far superior - they are inherently at the weight of the high number and have additives to make them flow at the low number; dino oils are the opposite. This means that when the oil additives are depleting, syn oils become "thicker," losing their cold-flowing capability while dino oils lose their hot viscosity "thickness," becoming thinner oils at operating temp. So eventually a 15W40 dino oil becomes a 15 weight oil while a 15W40 syn becomes a 40 weight oil.

 

[krush]

It takes very little oil flow to keep a film going on a plain bearing. I've worked on some pretty massive machines that just had oil slingers.

 

[MikeP]

"It takes very little oil flow to keep a film going on a plain bearing."

I agree. But I can't come up with any other mechanical reason that DD determined that multi syn oil wasn't working in the engines. There must have been some sort of problem and I can't see what else it could possibly have been other than some sort of issue with insufficient lubrication.

OTOH, I wouldn't want to actually pay for approx 6 gal of Mobil 1 (or whatever) for each engine! So dino 40wt is fine!

 

[rsmith]

Why would a MFG waste their time and money to aprove a new oil in a long out of production obsolete engine? Is Ford going to revise the specs for the model T to include synthetics?
Been using synthetic since 1978 in my engines and ONO generators. I worked briefly for BFI the second largest garbage co. All their trucks ran LE Monolec and did 50,000 mi drain intervals based on oil anylisis on random trucks.

http://www.le-international.com/uploads/documents/8420 - 8450 Flyer.pdf

 

[Trojan]

As Krush said it doesn't require much of an oil film to lube a bearing. But that depends on the dia., width, material its made of and the RPM it runs at. A good old example is the old solid lifter auto engines. When first started the engine would rattle like crazy. That was caused by usually by 3 things. Lack of oil pressure, large clearances, low viscosity oil. So we all raised the viscosity. 20W to 40w. now it's quite. Just think what that motor would sound like with synthetic oil. It probably would not last long even though the syn. is better. The washing out of a bearing do to high clearances, high ware and high pressure is very bad for the motor. Today motors are designed with very close tolerances, smaller diameters, as in rod and crank jernels, narrower bearing ways, higher oil pressures and higher RPM's and are able to run the thinner viscosity oils. I think the usage line for new Syn. oils and the old oils is the design age of the motor involved.

BILL

 

[MikeP]

True but there must be more to it - else why would a manufacturer, like Ferrari, who originally said 20w50 was right for it's 1975 V8, say twenty years later that 5W40 was recommended for that same 1975 engine? I've read the shop manuals for the engines concerned - their clearance tolerances were no better/worse than other manufacturers of the day. So those original clearances are now good for 5W40. Of course, actually the difference is just from 50 to 40. So in that regard, it's not really much of a change. People tend to fixate on the low number, thinking, "Oh my God, 5W40 is too thin for the engine." But, of course, it's 40 wt in normal operation.

OTOH, the fact the DD DID once say that 15w40 syn was ok for 71 series and then said, "oops," indicates that they found a problem. It wasn't a matter of not wanting to certify it for an obsolete engine because they did certify it as OK. Then they uncertified it.

 

[rsmith]

I would think the dancing horse people are more interested in the care of their legacy engines than most MFG. When was the DD recomendation made? was it while they were still making the 2 strokes of shortly there after? Did the recomendation to pull the aproval come from the legal dept to prevent liability? Seriously why would any MFG that is never going to make any money off a dead product open themselves up to the liability?

 

[MikeP]

Well, as I said, the DD 71 series engine manual that came with our 1980 Hatt says 15w40 is suitable. That manual had to have been published sometime prior to 1981. According to a post on another site (and I think it was mentioned here as well) the 8V71 is still being produced. From a post on the other site: "MTU builds the engines for military (NATO) 520 hp the DDEC 8v71 went out of production for civilian use in 2001"

 

[MikeP]

Just found this re DD two strokes;

"Multi-Vis Oils
Less than optimum engine life must be expected when using 15w-40 oils. Multi-vis oils tend to break down due to mechanical and thermal stress which results in a loss of viscosity and premature engine wear. Multi-vis oils do help cranking when temperatures are below 32 degrees F (0 degrees C). However, once the engine starts, the major advantage of the multi-vis oils is exhausted. When the engine reaches operating temperature, the internal engine temperatures and pressures vary little from an engine operating in much warmer climates. This is when the 2 cycle engine benefits from the superior protection of a 40 wt."

Note that the above seems to be referring to dino 15W40, not syn since syn multis go to the standard weight when the additives are depleted, not the W weight.

There are also some pics of oil wear comparisons on the page

http://www.tejascoach.com/ddcoil.html

 

[bobk]

I wonder if sulfated ash levels play into it with two stroke engines?

Bobk

 

[krush]

OTOH, I wouldn't want to actually pay for approx 6 gal of Mobil 1 (or whatever) for each engine! So dino 40wt is fine!

I worked briefly for BFI the second largest garbage co. All their trucks ran LE Monolec and did 50,000 mi drain intervals based on oil anylisis on random trucks.

Rsmith gives one solid reason for running synthetics. What if it lasts much longer?

Also, I've seen with my own eyes on my nasty sludged car engines how well synethic can clean stuff up. Synthetics often work so well that there is very little wear in places where we'd normally expect it!

 

[jim rosenthal]

I think it DOES last a lot longer, and I have no doubt that it does clean out sludged areas in the engine. Which makes me wonder, all over again, why I am not running it in my marine diesels. Damn it.

 

[MikeP]

Because all us sheep tend to run with the herd?

Hey - I was over on a Honda CBX site and they go through the same endless discussion/argument, whatever on what kind of oil to put in the CBX. It's the same on any site that talks about engines of any kind. All you can really do is your own research and decide based on that. SOmetimes the herd mentality is so strong it's nearly impossible to break, even if you really believe in a "new" way.

Example - a while back I rebuilt the tranny in my Norton Commando motorcycle. I decided that I would run ATF in the box instead of 90wt gear oil. I did that based on a lot of research concerning the type of gears (spurs), type of bushings (bronze) etc. I am ABSOLUTELY convinced that ATF is a better choice for that gearbox. I put in the ATF. It shifted great/acted great. Two weeks later I drained it and put in gear oil. I just couldn't bring myself to "argue" against the historical record of more than 60 years of putting gear oil in those boxes. But Dammit. I KNOW that ATF is better for this box...

OTOH, I have no difficulty in going to 0W40 in my car...go figure.

 

[Captcoop]

Jimmy,
My Cummins Operation & Maintenance manual recommends Valvoline premium Blue 2000.
Valvoline no longer makes this product. It was a blend of synthetic / petroleum. I emailed Cummins
and asked if the synthetic was OK and they said it was. I now use Valvoline blue extreme and
have had no oil related problems.
Good Luck, Lonnie
PS. I wouldnt worry about the warranty it is useless.