Hi everyone. Been a long term reader/lurker on random stuff throughout the years but finally decided to join. I have an 05 Liberty with the 3.7 engine. It has 160k miles on it and I've always changed the oil every 3-4k since I got it when it was 2 years old. Past year or so, it has seemed to start using oil, sometimes a quart per 1000 miles. But not always. I know it has a leak coming from the front crank seal (I think). It leaks enough to coat the oil pan but never drips. Not sure if it's burning or leaking more oil, tail pipe is not oily at all and there isn't an oily film on the back of it like I experienced with a Hemi Durango that burned oil badly. I also use the Jeep for a weekly commute that's 150 miles each way, sees about 350 miles a week. I used Valvoline Maxlife for two OCIs last year (switched from regular dino to HM at about 145000 miles) and that helped a bit, then I am now using Castrol HM oil, both 5w30. Strange thing is, after the oil change (first 500-1000 miles of the OCI) it does't use hardly any oil. After the oil gets some miles on it, the usage increases quite a bit. I check the oil before each leg of the trip. PCV valve is new as well. I guess my two main questions are... 1. Is that common for the HM oils to break down like that? Would I be better served going to a straight dino oil as oppossed to the Semi-synthetics like the ML and the Castrol HM? 2. What is the best way to isolate between leakage and oil burning? Sorry for the long winded post, if anyone can direct me to previous threads that cover this that would be great!