Do I have any direct experience with Schaeffers? No. But they certainly are capable products that consistently post good to excellent used oil analysis data, and they have earned a solid reputation for a reason.
The real issue has not been addressed, though. What are you OCI's going to be? I, too, have a Dmax and a Kubota (L3430). I put 5k miles a year on the Dmax and less than 100 hours a year on the Kub. Neither one accumulates enough use to warrant use of synthetics. Will yours?
If you're not putting a lot of miles on the equipment per year, then you're fooling yourself into thinking you're protecting the engines "better" by using any brand synthetic.
I honestly think you'd be impressed with both vehicle's used oil analysis even if you used a quality dino HDEO. If I had to take a total stab at an estimation ,(using memory as a guide from all the used oil analysis I've read), I'd say 8k miles on the Dmax is easily doable, and 10k is not out of the question at all. The Kub can likely go 150 hours or more. If you're not surpassing these points on a yearly basis, you're wasting money by running synthetics.
Want proof? Here's a link to a used oil analysis that shows 9k miles of use on an LBZ with CJ-4, and Blackstone recommended trying 11k miles! The wear was excellent. All on Mobil Delvac 1300 conventional 15w40 oil. (note: you'll notice that myself, Arkapigdiesel, and D-Roc are all members over there, too.) I'd put this used oil analysis up against any "synthetic" from any company!
http://www.dieselplace.com/forum/showthread.php?t=256262&highlight=cj-4+oil
If you're concerned about cold pumpability, then the semi-Schaeffers 15w40 may not be as good a choice as the full 9000 series. Or, if you're convinced that you just have to do two OCI's (one cold weather, one hot), then why in the world would you run a synthetic at all? You wouldn't accumlate enough mileage to make any difference. Here, a 10w30 could be for the cold and 15w40 for the heat, both dinos. Or ...
(I know this sounds like heresy
) for OCI's equivilant to 10k miles or less, you could run 10w30 year round. The Rotella and Delvac 1300 are availabe in those grades, and they are posting enviable used oil analysis, but only when people actually get off the stoop of prejudice, and give them a try!
And I'm willing to put my money where my mouth is; this fall I'm going to Rotella 10w30 in both the Dmax and the Kub for a year's OCI. When complete, I'll post used oil analysis in fall 2009. Want more proof? Check the post from Arkapigdiesel in the used oil analysis for his 10w30 CJ-4 Rotella ...
I don't mean to degrade your decision to get the Schaeffers; they are quality products. I just question anyone who thinks short OCIs and synthetics are going to be "better" somehow.