I've already got a separate thread with oil suggestions for my vehicles, but I wanted to make a separate thread here just for my Jeep. Little background: It currently has 280,400 miles, and I recently replaced the rear main seal and oil pan gasket, so there's no significant leaks. Actually haven't observed any significant oil loss either. It runs like a champ, although the fuel efficency isn't so great overall, it's good for what it is. Has 245/70/16 tires, lifted about 2" with an Old Man Emu/Bilstein 5100 shock combo that's popular with Jeep guys. Not the highest lift, but a great ride. Added some wheel spacers and the Jeep sits as I feel it should have from the factory, and I average about 14.7 mpg per the overhead computer. Not the most accurate gauge, sure, but the gauge read 17 mpg with stock tires at stock ride height. Currently I have Valvoline MaxLife 15w40 with a quart of Mobil1 HM 10w40, and a bit of Lucas oil stabilizer (yeah I guess that stuff is [censored] now!) and I feel like it may be a bit too thick for my Jeep. I do like the idea of the added protection though. So my question for you guys, is should I go ahead and run a 5w30 HM Synthetic like Castrol? Maybe go for an extended performance Synthetic? Or just stick to Syn-blends like Quaker State defy or Valvoline MaxLife? Rotella T6 has been the most recommended, but I don't have any sludge or leaks, so I wonder if I can get by with a 5w30 weight to improve efficiency. I'd like to hit about 15.5-16 mpg, but I don't want to sacrifice protection. I've read the Castrol Edge oils run a little thicker, and I know they have a nice gold color to their oil, which is nice haha I think the Pennzoil Plat may run too thin, however the Euro spec 0w40 may be nice for my Jeep, considering I don't have any oil leaks or significant oil burn off. I'm still learning the jargon around here (yes after 7+ years lol) but I think I understand that a thin Xw40 weight may be comparable to a thick Xw30 weight. Thoughts??