Thinner is better trend in gas engines

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Vaca

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Does anyone have any idea why there is not more discussion about using thinner oils in diesel engines like there is with gasoline engines?

I don't necessarily agree or disagree with the thinner is better trend in gas, but am just wondering why not with diesels.

A gasoline engine and a diesel engine have so much in common, the pistons, rings, crakshaft, bearings, camshaft, valvetrain, etc, etc......
 
Diesels operate at high loads at low rpm's whereas gas engines run at higher rpm. Diesels need heavier weight oil to keep the oil pressure up at those low rpm's to prevent bearing wear. I'm no expert but this how I understand it.
 
Oil pressure is not what prevents wear. Pressure only creates flow that is needed to supply oil to the engine.
The only place you really want pressure is in the bearings and that is supplied wedging effect of the oil being pulled through the bearing as it rotates. The oil pump has very little to do with it. If it did, you would not see engines without oil pumps like lawn mower engines.
Diesel engines need heavier oil because they spend a lot of time turning slow at high pressures. Thinner oils have time to squeeze out of the bearing and cam surfaces. When you add to that the soot that is in the oil it becomes important to keep a thicker film of oil in the bearings.
 
Vaca- We had this discussion some time back. Do a search. The comments were interesting, including some from Dr. Haas, the "Thinner is Better" guru. Well worth your time to search!
 
Aren't 15w40 and 5W-40 the same weight oil at normal operating temperatures?
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I can see a there might be a problem with someone using a 5w30 oil...but I don't see any problem using a 5W-40 oil in a diesel.
 
I'll be switching my 6.9L IDI Ford and Ford 2810 tractor to a 10w30 HDEO dino this fall. Plan to run this oil year round, but I will be doing used oil analysis to monitor. The 2810 experienced cranking trouble last winter and does not have an oil cooler/heater. I will keep one tractor, the tillage unit, on 15w40. Everyone who brings up sythetics has to send me a dollar. I know the drill and acknowledge the point on performance. It's just not a cost effective move on a tractor that gets less than 75 hours a year on an annual change. Especially this year, when a drought has all but destroyed my crops to the tune of about 40 percent of a normal wheat yield last week. My soybeans are about toast. The corn round here IS toast. Not much bio coming out of Putnam county this year.
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Jim- I just got 10 gallons of RT 10w30 on sale for $8.00/gallon. Is Schaeffers that inexpensive? It wasn't the last time I checked. Then add shipping.

I've got nothing whatever against Schaeffers... it's very fine oil... but when I've been getting fantastic used oil analysis on RT 15w40 and have used it on the same truck for 20 years. It's still running superbly, I might add, so what's my motivation to switch? Merely to spend more money?

Will I get the same service from the 10w30? I hope so. The RT 10w30 is a similar formulation to the 15w40 but I'll do my due-dilligence via used oil analysis to find out. My cold start issues on the 2810 were kinda borderline in severity and at the point where a 10w30 will likely take care of the problem, IMHO. It was a particularly cold winter for us. In weighing the aspects of the problem and all the alternatives, the RT 10w30 seemed the cost effective alternative (I wish I could find a LTCV spec for the RT-10W-30, though). With the truck, mpg and standardization are my main motivations. The truck was spec'ed for a 30 weight for my climate when new. The RT oils seem very shear stable and the CJ-4 10w30 starts out at a relatively thick 30 wt (12.1cSt @ 100c). In used oil analysis, the 15.7 cSt 40 wt (CI-4+) either stayed around 15 cSt or barely dropped into the 14s after 4-5K miles in this truck. This last 15w40 test will be at about 6K miles. BTW, This is my first foray into the CJ-4 spec oils as well. We'll see. I'll post the results.

You owe me a buck!
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Some diesels can get away with running a xW-30 with no problem. I believe it has to do with cylinder pressures vs RPM and bearing size. If the engine turns enough RPM and a low enough cylinder pressures then a lighter oil will work fine, epically in cold weather.

In most cases diesels will do much better on heavier oil. The exception might be the new high speed, small displacement passenger car diesels. I really don't have much experience with diesels that small in displacement other than in tractor applications.

Jim - I'll send ya two dollars, sounds like your having a rotten year, sorry to hear about harvest prospects.
 
Quote:

Hi Jim,
I can appreciate what you are going through, we are just coming out of six years of drought with over 7" of rain last month. We hadn't had 7" in the previous six months combined. One of our nearby rivers stopped flowing over two years ago (we bought a small block beside it a little while back) and it's so good to see it flowing again. I had an excavator dig a hole in the river bed just so we had a little water there for our pump.

Three of those years were spent running the FIL's cattle property (1700 acres, open range) and wasn't much fun. We de-stocked almost too late and hung on by our finger nails. Never really want to experience anything like that again.

and FWIW, while I run D1 in the Nissan and the Defender, the old Fiat tractor gets Fuchs CI-4 mineral oil as it only clocks up 40-50 hours a year, grading a dressage arena and slashing.

Click to expand...
 
One of the members of the TDI club used 0W30 Petro Canada diesel oil for 200,000 miles. His engine was showing very low wear based on UOA. He did have a bypass filter to keep the soot down.
 
My dad has been running Amsoil Series 3000 5w30 in his 99 Powerstroke for over a year and he has had excellent results. His oil pressure runs about the same as it did on RT and its starts much, much easier than it used to.
 
Yea the way I heard it was one reason the oil is thick so that a thicer oil film stays between the bearings. That keeps soot form "trying to help" seperate the bearing surfaces. Soot is just a dirty way of saying dirt.
If you can keep the oil clean like a gasser then maybe you can go a little thinner.
 
Do you think the viscosity of the oil at the point of the wedge in a main bearing shows much difference between a 30 and a 40 weight oil and operating temperature?
 
High compression = thicker oil needed. Some diesels have a 17:1 compression ratio. Don't over look Conoco's HD 15w40 Fleet Supreme diesel oil.
 
I guess then that means with my 16.3:1 in my Dodge Ram, I could use a 30 weight oil if I so desired, but I do stick with the 40 weight. In fact, I've got Maxima's petroleum 10w40 in there now.

Keeping a cloe eye on it, both color and "feeling" wise. I know, not scientific, but so far so good...
 
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