JA, by cold weather package I mean equipment for cold weather, including but not limited to aux heaters. On a lot of equipment I have worked on the cold weather package includes things like battery heaters, fuel heaters, oil heaters, larger batteries and possibly a 24v starting system where the comparable model would have a 12v starter. Also cold weather starting aids like a KBI ether injection system are common cold weather package items. I completely agree with you in that a lighter weight oil would certainly be much easier to pull off. A 10w30 HDEO would be fine in those tractors, although I'd keep and eye on the little Ford and see what it does in the summer with no cooler (probably just fine).
Dr Haas, I understand that the numbers you gave were for demonstration only, but they did get the point across. One thing that I'd like to comment on is the fact that you reference cars quite frequently, and the type of engines in trucks and equipment that I've mostly been referring to (as I think JA's question was directed mainly at HD stuff) is quite a bit different than a car or even an Expedition. Most diesel engines, MD on up, run engine coolant to engine oil coolers and never get more than about 200*F sump temps. The highest temps I've seen were in a Cummins BCIV 440. I was in 99-103*F ambient temps and pulling a combined weight of about 175,000 lbs up a 11% grade for near 20 minuets. For reference, most highway trucks are only 80,000 lbs combined, local (such as dumps) maybe 105,000 assuming no special permits. Also, mandated by the Feds, no highway has a grade greater than 7%. After 20 minuets of slow speed (about 11MPH was it), no ram air to speak of, and full throttle at governed full load speed I only saw 255*F in the sump. Most of the other equipment I've been involved in would run less temp in this condition, but this truck was fairly underpowered for what I was doing with it. Now, most of the engine manufactures that I'm dealing with here recommend 15w40, and only in cold weather due some of these manufactures allow 10w30.
One of the differences I think are fairly important in dealing with oil weight is the engine design. Diesel engines are typically designed with very regulated operating parameters compared to a gas engine. You can over-rev a diesel under load unless someone has mis-adjusted a mechanically governed engine. Bearing clearances are typically larger, as are cam bearing clearances and most modern gas engines have hydraulic zero lash overheads, something most diesel do not have.
I would think that in a close clearance engine, such as an Expedition or a more exotic high performance car, a 20wt oil has plenty of film thickness to support items such items as the main and cam bearings. In most diesel engines I would think the same film thickness would not be sufficient since the clearances are larger to begin with, the downward power stroke would cause the rod and crank to “get a run” at the bearing until the oil film thickness started to really support the load. I mentioned this in a previous post, but I'll do so again because I really haven't made my mind up yet, I'll have to play some more. I would think that as RPM increases, the time of power impulses decreases. Another way to think about this is, the time it takes for the power stroke and for the piston to change direction is shorter. Load may actually be less due to changes in cylinder pressures associated with RPM and load changes. This condition would reduce the amount of oil squeezed from the journals. Think of it this way. If you have a water logged dirt patch and you walk slowly across it, you sink further and more water is displaced around you boot. If you run across the same area, less water is displaced if the speed is great enough. Not sure that was the best example, but it's been a long day.
I certainly agree that thinner oils can be used with great success. I think that thinner is always better is most certainly not true. If UOA's are used then I'll try almost anything (esp. when the boss is on vacation). There are various types of equipment I've tried switching from 15w40 to 5 or 10w30 and didn't have much luck, again the track record of 5/15w40 oils is pretty good, although that is certainly open for challenge. I've run some pretty thin oils in the race cars with good results, so I know that thin oils due have the ability to work well. I suppose I'm taking this all too seriously in that Jim Allen only want to go down to around a 10w30 and no run a 0w10 in his diesel pickup. Ok, I guess I'll go back to my corner now
