I am currently running Mobil 1 HM 10W30 in my 2003 PT Cruiser (a little over 90,000 miles now and runs great). I've had great success with this oil and switched from Castrol (German) 0W30 when my stash ran out (ran from about 25,000 miles...great UOA's). Now that Mobil 1 has introduced a HM 5W30 I thought I'd consider switching to it as I assumed it would be a little "thinner" and better for the upcoming winter and it's subzero temperatures here. Just for giggles I thought I'd check out the MSDS stats on the two oils. The HM 5W30 is rated at 78 cST @ 40C and 11.8 cST @ 100C with a pour point of -33F. The HM 10W30 is rated at 62.6 cST @ 40C and 10.1 cST @ 100C with a pour point of -44F. What gives? I'm certainly no expert but it would appear that the HM10W30 is...thinner and has a lower pour point? I can't get the HM5W30 around here but can get the HM10W30 at Wally world in 5 qt. jugs (PT has a 5 qt. sump). At 5,000 miles the dipstick indicates about 1/4 qt. of usage...excellent I'd say considering the miles. This isn't my daily driver anymore and the oil gets changed out twice a year or so. At this point I'm inclined to just stick with the HM10W30 and call it a day. Appreciate any input...