I got some info back from Amsoil regarding these two fluids and the topic at hand. Ryan Lawrey emailed me from their tech service center.
First, Amsoil was unwilling to share the raw data with me. I only got a synopsis sheet and some written words. That really limits my ability to make more detailed conclusions. We'll have to go at face value here and understand the limitations of the conclusions. Amsoil presumably paid a third-party entity to perform this test, but again I have no direct info of any such like. I can only guess, as they won't share the raw data, nor even the test observations.
One has to understand the test protocol.
The DDC DFS 93K222 is a test to check for the effect of lubricity in terms of three criteria, using a DD13 engine:
1) cylinder wall scuffing
2) top ring weight loss
3) Fe rate increase of 25ppm in UOA data (note this is WEAR RATE INCREASE, not total accumulation)
- The test is run for "up to" 200 hours or until a violation of the above criteria occurs.
- The minimum "pass" threshold is 30 hours. IOW, you can "pass" at 30 hours, and every hour after that is "better" than passing. (Amsoil "passed" with the HD at 150 hours; the Signature at 200 hours at the max limit of the test).
- The test is run at 244 degF (118 C) for the gallery oil temp. The coolant is run at 221 degF (105 C). (note, this is typical of many SAE and ASTM tests; those who fear "hot" oil are needlessly worrying about minutia, because 250F is NORMAL oil testing temps, for hour upon hour upon hour. If your engine oil gets up to 275F for a few minutes for an uphill pull, and then drops right back down to 215F, you're fine; don't spaz out.)
- The first 30 hours is run at 50% throttle loading; the next 170 hours run at 80% rated load. In context, this would be like running down the interstate at 50% load for 1800 miles, then uphill at 80% load for a remaining 10,200 miles. (this presumes an average 60mph speed; 200 hours is 12k miles total).
This is an ALT (accelerated life-cycle test). They purposely infuse a harsh condition for extended constant hours to fast-forward the results. It's done all the time in labs to give a desired outcome. And at times, it's very helpful. Sometimes, it's not a real indication of how things work because inputs are not always run on an even keel (aka the infamous GM filtration test, but I digress ... ). I would presume this test is at least somewhat helpful if you ran OTR rigs heavily laden; TT would likely get more out of this info than us normal guys. Why? Because your Powerstroke or Duramax does NOT run at 80% WOT for 170 straight hours! No - most of you drive your rig slightly loaded down to the boat dock or pull your 5ver a few weekends a year. The rest of the time you're probably running lightly loaded. The take-away concept here is that just because this test shows some manner of useful info, do NOT presume it's applicable to all situations and all manner of use. Hence, the results only speak to certain test conditions as inputs deriving one output result. It's completely wrong to presume that your situation will reveal similar results.
How does this test communicate relevant info to us? By implication of a relative pass/fail nature. But we cannot easily replicate the test nor the measurables, in general, home. None of us are ever going to drive with a 15k pound back-hoe on a trailer, from DC to Sacramento on I-70, for 7 days non-stop, uphill the entire way at 80% throttle. Nor will we pull an engine apart to check for cylinder scuffing or ring weight loss; we don't have the time/money to do this. However, we can do UOAs. Even Amsoil uses UOAs for OCI extensions. I don't have the written test methodology, but if I understand the SWRI document, they use the UOA Fe ppm as a trigger to suspect scuffing. Once they pass a 25ppm Fe rate increase, they then pull the engine apart to check the physical condition of parts. That in mind, a "pass" of the DDC test is considered acceptable for any fluid that goes longer than 30 hours in duration. The test is simply pass/fail. If any of the criteria are violated, it's a "fail". The contending fluids can "pass" at 30 hours, or more, but never less.
Amsoil's two lubes (PAO syns) were run against the test conditions, and "passed" with flying colors. They ran these against a conventional off-the-shelf (yet undisclosed brand) 15w-40 lube. They essentially did two things; they ran against the test standard and they also ran against a dino oil.
But ask yourself a few things ...
How would another syn competitor fare? Probably very well. Apples to apples is what I like to see.
How many times do you run 80% of rated max power for SEVEN non-stop 24-hour days?
How would this test have differed if the loading was more "normal" to real life conditions?
Don't freak out here. You're not going to get cylinder scuffing in your Cummins or Powerstroke running a dino lube to 10+k miles. Remember they manipulate the conditions to cause a severely accelerated wear rate. Our typical UOAs show wear rates DROPPING during the first 15k miles, even using conventional lubes. This is why I preach that real world use is not often replicated in lab tests. This would ONLY apply to you if your wear RATE jumped by 25ppm per unit of measure. IOW, if your engine sheds 15ppm in 10k miles, then your wear rate is 1.5ppm/1k miles. So to trigger the DDC "failure" point, your engine would have to start shedding 26.5ppm per 1k miles! You'd have to experience 318ppm accumulated in 12k miles to trigger the scuffing condition failure associated with the DDC test. Kind of puts this test in perspective does it not?
The Amsoil lubes did really well. So would most any other syn I suspect. And the conventional did well, too; it surpassed the test by 20% under the most unnatural conditions most of us will never see.