Same here. bought a changes' worth of the Castrol [dyno, not syn] product when on sale around Xmas. Its in the truck now and seems to be fine. I've always liked Castrol products in my Euro gassers, have to think its comparable to the Exxon/Shell etc. products.
I put the castrol GTX diesel 15-40 in my truck this oil change. I was also very weary seeing all the posts for everything but the Castrol on this site. I thought it might be causing my cackle and cold rattle but the specs seem pretty high on it. I'm going to switch to Delo 400 15-40 and give it a whirl next time. Still considering for winter the synthetics. After racing briggs gokarts for 17 years I have first hand knowledge of how good the synthetic oils are. They are incredible.
Roadfrog, I've seen mention of the Wallyworld(the death of small town America) oil before and thought I had checked thier price before. I didn't see where it was much, if any, cheaper than Rotella. I'll have to look again.