ghillie – I’m going to alternate Delvac I and Amsoil every 7500 miles for at least 2 cycles. The idea is to average the two oils over a variety of conditions (age of engine, towing, not towing, cold vs warm weather). Haven’t decided whether to use an Amsoil or Statapore filter, but the filter will always be the same. I will change the air filter every other oil change. I can only put on about 15,000 per year, so the test will take some time. The null hypothesis (that which the data will try to disprove) is that there will be no significant difference between the two oils. If I use the same oil twice in a row, I would be comparing wear metal accumulating in an engine 15,000 miles older with the second oil. It would then take 4 years to get in two test cycles. I do overnight drains, so I don’t think the amount of oil carried over would be significant.
Of course the results of one vehicle with one driver won’t allow any serious conclusions unless there are large differences between the oils. But if a couple other guys were to try this, we might be able to get enough statistics to uncover a significant difference, if there is one. Since these are both top of the line PAO based oils, there is no risk in doing the test. Once I decide on one oil, I’m going to go the bypass filter/extended drain route, which is the only cost effective way to use synthetics.
I’ve given the matter lubricant performance a bit of though and have decided that there is no way we are going to get meaningful product comparisons from the lubrication industry. There are two types of information out there: 1) laboratory tests that have been explained in great detail in the various threads relating to crankcase and differential lubes and; 2) test data from over the road truck fleets. The limitations of extrapolating lab tests, most of which were designed for gear lubes, have been debated in detail by the lube techs both here and at the F**d site. The fleet tests would seem to be more meaningful. However, most of us don’t drive out pickups the way over the road truckers drive their rigs. We have smaller crankcases, more cold starts, and more short trip. So I think the only way to learn if there is a “best” lubricant for our purpose is to do our own testing.
Before I get flamed, this really has nothing to do with cost effectiveness. I’m just an enthusiast who wants to use the best oil possible because of an obsessive compulsive disorder. But Pete, if there are no differences, I'd pinch a penny the same as you and go with the least expensive product.
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1999 Quad cab 2500, SB, SLT, 4X4, 5-speed, 3. 54, tow and camper package, Lance 820 camper, Lance cabover stabilizers, Rancho 9000s, Airlift airbags