Thin is Better: The Gospel According to A.E. Haas

[Jim Allen]

I've been reading and re-reading Dr. Haas' treatise on Motor Oil (see http://theoildrop.server101.com/forums/s...ge=0#Post258506 ). It makes a lot of sense and I wonder if his "thinner is better" philosophy applies to diesels. In theory, of course it does, but given the much higher cylinder pressures of a diesel and the higher low rpm loads, I wonder if there are any serious downsides to running an oil like a Delo 400 0W-30. Not just "Uncle Joe" warnings and tales designed to maintain the status quo, but more serious research. I'll be doing some of that but this might be a good discussion once you've read the material. If you haven't read is Motor Oil 101, et alia, it's good, thought provoking stuff based on sound principles as far as I can see. My only question conncern it's applicability to the world of compression-ignition powerplants. I haven't been able to find much information on that aspect, though anecdotally there have been a lot of diesel manufacturers that specify a 30 or 10w30 wt oil.

Everyone seems to think diesels "gotta have" a 40wt oil and G-d will smite thee if you don't. I've been using 15w40 for decades and after a winter no-crank experience recently, I have religion over getting that "W" number lower, at least on the tractor that's gotta start for me. Cheap ba----d that I am, I still want to run a single grade for my "fleet" of two tractors and diesel pickup. I'm looking into the aforementioned Delo 0w30 and regardless of anything else, the fleet will be going to a 10w30 HDEO of some type, maybe even a syn or syn blend.

 

[wileyE]

I personally wouldn't go there with a diesel, for the same reason I think their hole in the thinner is better arguement for gas engines. The hole would be if the engine is lugged or run with heavy loads at low rpm. The oil pump is rpm dependant and the oil pressure is lower. One may argue that the pressure is sufficient, but vicosity and pressure combine to make the needed cushion at the bearing. Take one of those two away and load the bearing hard and you might not have adaquate protection. Additional EP additive may cover the situation, but we don't see that in todays off the shelf oil. Also let me rant that "synthetic" is not a substitue for wrong viscosity or replacement for lower or additive levels.

 

[1040 WreckerMan]

I think that thin oil is perfectly acceptable in a diesel engine if the design and operating conditions allow for it. If the engine was designed for thiner oils (and most are not from what I've seen. That will most likely be changing just like the gas pot world) then go for it.

In a diesel engine, I would want to see very large rod and main bearings, with very rigid backing material that is also temperature stable. The oil pump drive speed would also need to be adjusted most likely to keep the flow sufficient with the thiner oil.

The problem I see with running thiner oils in diesel are mostly load based. Diesel engines have a very slow, long and pronounced power stroke compared to a gas engine. This tends to put very high bearing loads on the rod, main and piston pin areas. In addition to the high bearing loads, the loads are fairly long so there is plenty of time to squeeze the oil out of the bearing.

One of the reasons that I rarely recommend an oil that is thinner than 5/15w40 is first these oils have a tremendously good tract record for quite a few years. They also tend to work fine over a very wide temperature range. I find that most cold weather operation problem are usually, but not always, a result of some other system that is either faulty or in need of service. For example, a friend of mine had three pieces of equipment up north that were broken. He doesn't have a lot of money and could afford to be without the equipment for a while and the stuff sat for just shy of 4 weeks in very cold weather. From what he tells me the warmest day that month was the day I arrived to work on the equipment and it was 12*F. By the time I was done working on the first piece of equipment it was well below zero (thermostat in the truck read -22*F, who knows what it really was). With a good charge in the batteries and good winter fuel the engine fired right up with 5w40.

The drawback that I see in this situation is due to the thicker oil you would not want to run the engine hard until the oil temp has come up.

I would think that in a tractor, especially one that sees high engine speed, would due fine on a thiner oil. Since a tractor is more or less constant load combine with the higher RPM would tend to be easier for the thiner oil to stay in the bearings. Even in the industry there seems to be some debate as to whether thing or thick oils cool better, so I'll leave that item for someone else to touch on. A thiner oil would tend to flush debris out of the bearings quicker, however there should be anything of any size to flush out in most cases.

As always, UOAs will tell the tale.

 

[Tim]

We've seen more than a few xw-30 analyses over the years in TDIs that had notably more wear metal than comparable 40wt oil analyses. Too much to ignore, I think.

That's just one engine...but one that many might think would be more suited to a lighter weight oil than some other diesels out there.

I still wonder how Amsoil S-3000 5w30 would have worked in that engine.

 

[vmcboss]

I am now testing Amsoil 5W30HDD in my 2003 Sprinter, it has 110K on M1 0W40. I will post the analysis at 5K and 10K. I agree it depends on the engine and its use, I will continue to use dino 15W40 in my two Cat 3406Bs.

 

[Steve S]

Jim ,I would use the manufactures recommended oil viscosity for the ambient temperature. Diesel engine manufactures know what oil will give you the longest life and best service.

 

[Jim Allen]

WileyE- Haas contends that VOLUME not pressure is the telling tale and that with a lower viscosity, your lubrication system will offer more oil volume at a lower pressure than a higher viscosity oil. More oil volume equals more hydrodynamic lubrication and better cooling, according to Haas. I plan on installing oil pressure gauges on all my stuff (the truck has one, but it's not marked with PSI) and monitoring pressure with the current oil. What I may do is compare my current pressure with those noted by the engine mfr. If mine is significantly higher at operating temps, especially in the hottest time of the year (about 90F tops), that may be an indication I can safely go to a lower vis. This also somewhat follows along with Haas' reasoning that viscosity should be tailored to ambient temp and use (his main criteria is rpms, appropriate since the discussion is often abour race cars).

1040- The above comment applies to you as well. Can't argue with the track record, as you say, because I have benifitted from it...but my starting problem was directly related to the 15w40 oil. Couldn't spin it over fast enough at -10, even with a good battery (depleted by cold). When supplemented by warm dual Optimas and the 160 amp alternator on my truck, it still spun over slowly but It finally did start. As to use, I see your point. It's a small tractor (3-cylinder Ford 2810) that's mostly used for light utility work around a small farm 50-70 hours a year max. It does some fairly hard, steady work at planting time as I use it with my grain drill. My pickup sees some hard use intermitttently, but mostly light work these days. About 75 percent of its 130K was towing, however.

VCMboss- I found a few very good reports of the Amsoil 5w30HDD on engine roughly comperable to mine- the pickup at least. Also a couple on the Amsoil 10w30. The cost of these products puts me off, however. The tractors in question get an annual oil change. The big tractor usually gets less than 100 hours per year. The little tractor 50-70. The Ford pickup about 6000 miles year or less and I've been doing 4K/year and had good UOA so I've bumped it to 5K.

Tim- I looked at the 0w30 and 5w30 TDI UOAs listed here and didn't see any major proioblems, except on with people using gas engine rated oil or running the oil too long. Maybe you have a different source of info than BITOG. In any case, two low-speed industrial engines and an older IDI 6.9L diesel can hardly be compared to those fast spinning, sweet little TDIs.

SteveS- All three of my engines list 30 wt in my temp range, either 5w30 or 10w30 (the old tractor actually lists 20wt for cold weather... but that was 37 years ago). I've never run anything but 15w40 in the pickup the past 20 years. The big International 826 ran most of its 8200 hours on Case-IH straight 30. The little Ford had 10w30 in it when purchased five years ago, but I switched it to 15w40. I don't know it's history, as it came from a dealer.

Equipment-

1986 Ford F-250HD 4x4, 6.9L IDI diesel w/aftermarket turbo 130K miles

'89 Ford 2810 tractor, 3-cyl 152ci, 38hp, NA, 2200 rpm max., 3000hrs

'70 IH 826 tractor, 6-cyl, 358ci, 103hp, NA, 2400rpm max, 8200 hrs

 

[Wrehch]

Thinner is better to a point. My personal opinion is that heavy diesel engines found in road tractors should not be run on anything thinner than 10w30 and that should only be used in hot weather operation or in engines that spec it.

 

[AEHaas]

I was asked to jump in here. First, the oil pressure is not important except to move oil. The oil pressure may be 40 or 70 or 90, so what - the bearing pressure is several hundred or even thousand. Oil pressure does not lubricate anything, only flow does the job.

As far as choosing the wt. of the oil, I advocate finding out what your particular requirements are for your application and your engine. This gives you the running (operating temperature) grade to use be it a 30 or 40 wt. But in all cases use the lowest starting grade such as a 0W- or 5W- , although, this assumes there is no loss of viscosity grade over time.

A 0W-40 may not be as shear stable as a 15w40, but if it is as stable then you would certainly want the 0W-40.

aehaas

 

[Rickey]

"Oil pressure does not lubricate anything, only flow does the job."

In the absence of adequate viscosity for the application,and conditions;flow alone will not guarantee proper lubrication.

Here again I recommend kerosene or other suitably thin light oil loaded with anyones favorite anti-wear adds (no viscosity increase allowed because thin is in).Put this in the voulinter diesel engine and go torture it.Look for proof, its in the testing! Maybe this will even exceed Slick 50"s results!

Oil pressure is an indicator of viscosity. Noted that this relationship is not exclusive. And lack of sufficient oil pressure can indicate a situation where an oil's viscosity is insufficient to support existing bearing loads.
High operating temperatures,high loading,and diminished viscosity due to the high temperature often coincide with maximum loading and extreme operating conditions.
Flame away.

Rickey

 

[1040 WreckerMan]

JA - I would certainly agree that pressure is not the end all be all of lube considerations. Pressure is an indication of resistance of flow. The problem is with the way these oiling systems are designed, we have no definite way to asses directly if we have supplied enough oil for the job when we start using thiner oils because pressure has been used since there were IC engines as the tell tale.

I have quite a bit of respect for the writing and ideas that Dr Haas has shared with us. It has certainly caused me to explore ideas I had more or less written off and led to many hours of new research and field tests that I have done. While the fundamentals are certainly applicable to any engine, thinner is better works with more success in a higher RPM application where the frequency of bearing load impulses is both higher and “lighter.”

I think the lack of a cold weather starting package was as much of a problem as the oil weight. A well formulated 30wt oil will probably improve the UOA's in that tractor during cold weather, and probably would return comparable UOA's in warmer weather. The only way to know is to try it and see how it works. I would work my way from the top down. It's a fairly safe bet that almost all diesel engines (medium duty and up, including industrial and AG engines) except for a FEW VERY recent exceptions were designed for 15w40, so I would start with a 5w40 and if that is still too thick go down to a 0w40 then a 10w30, etc. UOA's are obviously a must to determine whether the oil is hold up or not.

What needs to happen for the engine to live with any given oil viscosity? Basically we need to have enough pressure to move oil at a sufficient volume. The oil needs to have enough EP/AW additives to hold up areas like the overhead (rockers/cam followers, etc.). The oil needs to have enough contamination control. The oil also has to have enough viscosity and shear stability to resist being pushed out of cam, main and rod bearings during moments of high load.

How about mechanically? The oil pumps ability to move oil changes with viscosity. As I said earlier pressure gauges are used to estimate the condition of the oiling system. Flow meters are far to expensive and plumbing them would be a somewhat interesting debate all in itself. So, we really have no way to know how much flow we are ACTUALLY producing when changing viscosities, particularly important with changes to the “extreme.” Determining the operating parameters in a typical closed hydraulic system is much easier than in the open “total loss” system that the engine uses. These terms are not applied to the letter of their definition, but I did it anyway.

When I get some time (yea right) to burn, I'd like to use a small diesel powered tractor at the shop and rig up some pressure and flow gauges at various points in the system and see just what happens with viscosity extremes during cold and hot operating conditions. Ooowwww, my head hurts now, thanks a lot guys – I went all day without thinking and now look what happened.

 

[Shannow]

My Nissan (3 litre, 110kW) specs a 10w30 HDEO. I end up having to use xw-40 PCMO, because they also specify nothing better than CF-4.

If I could, I'd be using 10w30 exclusively...it's worth a couple MPG in this engine (based on the factory fill versus what I've been running).

 

[Jim Allen]

Some thoughtful comments.

1040 WM- Define "cold weather package?" If you mean plugged in... I wish! Until another building is built this year, it has to live in a 150 year old barn with no electricity. The tractor has a glow system.... about three minutes worth on a cold day is usually enough. I just couldn't get it spinning over fast enough. And, yes, I had winter fuel that was not gelled. I just started it again at about 20 degrees and it lit off first kick, but it still spins over a lot more slowly than on warmer days.

As far as your "top down" approach goes, that's running parallel to my thinking. I am going to install oil pressure gauges on all three units and likely oil temp (for sure on the truck). I have researched and found the factory viscosity recommendations (they all center around 30wt for my climate) and found the oil pressure @ rpm specs. I will test with the 15W40 that's in there now and compare the oil pressure specs with those listed for the engine. Given that my oil is thicker than specified for my climate, likely go with a 10w30 HDEO (Rotella or Delo) in the fall and test again. The cost of the syns really puts me off (minimum of about triple what I pay now). I'll monitor the next season with the new configuration and UOAs. I have good UOAs now (at least on the truck and 826) and I'll use thame as baselines. I'm not looking for all the perfection money can buy, just acceptable and cost effective performance. BTW, two of the three engines (not the little Ford tractor though) have water to oil oil coolers, so they warm the oil on startup as well.

Rickey- No flames! I am the model of civility!

You make good points about temps, viscosity and loading and I think my comments above acknowledge them. I would also offer, as I think Doc Haas might, that: A) the viscosity difference between 20 and 40 weight oils is not that huge. And: B) I don't think kerosene can be used as a valid comparison in this argument because it's so far out of bounds with engine design reality. According to a chart I just looked at, kerosene has a viscosity of 2.405 cSt @ 40C, just a few steps above water. The range for 20wt oils starts at over 30cSt and rises to nearly 80 cSt. Even 10 wt is in the mid 20 cSt range! As 1040WM mentioned, the oil pumps in IC engines are designed for a certain amount of viscosity. There is likely a lower limit where they lose a great deal of effiiciency. I think at "normal" ambient temps, we're safe in the 20-40 st range, though I would imagine that could be variable from engine to engine.

 

[Steve S]

Jim,when cold you can use a lower visc. oil. I have posted this before but I will again ,I had a boat which I made a preluber oil pump from a small eletric forklift power steering hydraulic pump adapted to a drill . Anyway one winter I wanted to go for a boat ride in 29f degree weather .The drill motor smoked by the time the psi reached 50 psi , Summer temps usually run around 100 f degrees the drill worked to 80 psi with out effort . 15w/40 delo was used in both occasions .

 

[AEHaas]

Kerosene that is fully additive formulated may make a good oil. The viscosity at 40 C is in the neighborhood of a 20 wt. oil's viscosity at 150 C. Now, if the kerosene did not thin with increasing temperature we may have a perfectly good oil. Not all fluids thin with temperature. For example, from about 0 C to 100 C water has a fairly constant viscosity of 1.

aehaas

 

[Jim Allen]

I just looked up kerosene and it showed 2.4 cSt @ 40. Another spec lists it at > 1.3 cSt. Yet another 1.7cSt @ 40C. A 20W is between about 30-80 cSt @ 40C. Am I missing something?

 

[AEHaas]

IF a 20 wt. oil was at normal operating temperature in my Expedition at 212 F the viscosity would be around 7 or 8 cS. IF I was pulling a load mid-summer the temperature of the oil may be 304 F (all sump temperatures - as this is what can be measured easily). Point temperatures inside the engine vary considerably.

So I would be driving around with an oil having a viscosity around 2 cS. This is what the viscosity approximates at 304 F sump temperature. NOW, if the kerosene viscosity was stable with temperature, as with water, then the viscosity of the kerosene would be around 2 cS at 304 F. And if the additives were the same or similar as with any SM rated oil, then my Ford would have no trouble using kerosene as a lubricant.

What I am saying is that oils thin to a viscosity of 2 cS with high temperature load use of your car. This value is not a bad one. Given the above, there would be no thickening with engine shut down so there may be little or no start up wear as the oil is already the appropriate viscosity for full load and RPM operating. No start up wear.

Understand that Normally formulated oil will lubricate an Expedition at a thickness of 2 cS. A fluid of that consistency (although Seemingly too thin to be pumped and work in your engine) is EXACTLY what does work in your HOT engine right now. Your engine can in fact pump a lubricant as thin a kerosene right now!

aehaas

 

[Jim Allen]

Is the a chart, graph or formula that allows you to approximate viscosity from a starting point (say a 12cSt 30wt @ 100C) and figure what it's viscosity woulbe be at another temperature?

 

[ffxfina3]

Quote:

---

My Nissan (3 litre, 110kW) specs a 10w30 HDEO. I end up having to use xw-40 PCMO, because they also specify nothing better than CF-4.

---

Shannow, perhaps your application is a little different than what is typical. Does Nissan really say that you can't run any oil that supercedes CF-4? According to the API, CI-4, CH-4, and CG-4 can all be used in place of CF-4. I'm not saying you are wrong, I'm just curious.

 

[JAG]

How did you get 2.0 cst at 304F? 427Z06 has posted kinematic viscosities of many oils up to 150C = 302F. M1 0W-20 KV was 3.7 cst at 302F. But it is bearings that must be protected so high shear rate must be accounted for. The temperature in the bearing will be higher than the sump temp which we've assumed to be 304F. I don't know how to account for high temp high shear rate viscosity at temps well above 302F so using HTHS values is best I can do. M1 5W-20's HTHS is 2.6 cP (NOT cst). I doubt we can look up the HTHS of kerosene so that puts us back to comparing kinematic viscosities again.

In summary, as said above, M1 0W-20's KV at 302F was 3.7 cst.

Is your sump temp in your Expedition really 304F during towing in the summer? If so, it needs an oil cooler. I test oils at 320F and even lower and even the best of the synthetics get beaten up badly when at those temps for even less than 2 hours. That's without having to deal with blowby products too.