I have been wondering, it seems a lot of people are using very light oil....the owners manual for my 94 Trooper calls for 20W50 in the summer, anything as low as 5W30 is strictly for temps below 40 degreesF. I was wondering why people are using such light oil when at the same time a lot of people are seemingly have oil pressure issues (the manual also calls out a minimum of only 8 lbs pressure at idle...even with over 150K miles mine does that no problem, as long as I have the specified weight oil for the ambient temps).