Hi all-decided to see what all the heavy oil hype was about and tried it in my 1997 Dodge B2500 van which is a Roadtrek motorhome conversion with a 5.2 (318) engine. Mileage is about 140K and I have always run 10/30W as per specs. I use a Scanguage II to monitor performance. Decided to use 10/40 for the summer months thinking it would offer a little more protection. Usual operating temperatures are around 198 degrees which climbs when pulling mountain grades. Oil pressure is noticeably higher (3/4 on the analog gauge instead of the usual 1/2 way) and temps seem to be consistently higher. Today when pulling a long 6 mile grade up the mountain, the temp rose to 215-218 instead of the usual 204-206. Does the heavier oil (Valvoline MaxLife 10/40) really make that much of a difference???