so for the last 10 k, I have been putting 15w-40 in my 96 F-250 i'm currently at 200k on the odo. but I recently noticed that she started burning oil. i'm getting ready for an oil change but my question is should i change back to like a 10w-40, or a straight 30 weight, or just keep burning 15w-40, I know diesel oil and gasser oil are different but the 15w-40 was added in their and seemed to help her run a little bit cooler, but for all I know I'm missing out on proper oil additives internally right now. and as far as the oil burning goes, well she's an older pick-up so at this point my plan is to keep adding. and thoughts suggestions would be greatly appreciated.