Originally Posted By: Chris142
Ok here is my plan. I want to spike Supertech 15w-40 with it. I want more Zinc and to make the oil a little thicker.
Truck holds 12 gallons. Should I add about 12 bottles of the Red bottls STP?
That would give you 18 cSt approx. Since the Red is for 4 cyl engine, it would be a ratio of one bottle to 4 qts, so your numbers are right on. There are a couple of serious considerations:
1) Will any STP product hold up to the higher bearing loads of a diesel? Better call them and make sure. Of course it's a diesel if it holds 12 gallons, right?
2) If you are trying to get rid of some existing oil then you are stuck, but if not, find something thicker and better.
3) Why do you want the oil thicker?
4) Redline makes a nice diesel oil with gobs of zddp, all that you could need or want.
5) If you really have a diesel, I expect you will get better info posting a question in the diesel forum at this site.