My apologies sir, I did not mean to come off as ignorant, and I do not know much of anything when it come to diesels so I wish to not sound like a know it all, because I do not know much at all (try to learn a little every day), and only know what I get from here and random diesel classes. However, when I saw the statement that 10w-30 was not engineered for diesels I became very frustrated because I hear this statement a lot. It is recommened by Ford to run a 10w-30 when below 30 degrees, so right now around here lol. If you wish to purchase 10w-30 in your area I would recommend checking with your local Ford dealer, thats what they start putting in trucks around here at the start of November. It has helped tremendously with cold and very cold starts. Again I apologize for the way the previous post came off and hope that you do not think of me as a super star, just trying to demonstrate a point (that was probably done poorly and with out good taste).