I've always had good luck with TropArtic. Looks like the 5W20 and 5W30 are now going to be synthetic blends. click on the August 3, 2004 Press Release CONOCOPHILLIPS UPGRADES SELECTED CONVENTIONAL MOTOR OILS TO SYNTHETIC BLENDS FOR ILSAC GF-4 Major Lubricants Provider Embraces “Good Just Got Better” Strategy with Massive Upgrade Beginning with its 5W-20 and 5W-30 Grade Oils HOUSTON, TX - ConocoPhillips Company, a leading global petroleum company and the fourth largest lubricants supplier in the U.S., today announced the company will upgrade selected conventional motor oils to synthetic blends, beginning immediately with its 5W-20 and 5W-30 mainline conventional oils. The robust product upgrade affects all four of ConocoPhillips’ “Family of Brands,” including Kendall, Phillips 66, 76 and Conoco motor oil brands. The initiative began as the company commenced reformulating its products to meet the latest ILSAC GF-4 specification. According to Scott McQueen, director of automotive products for ConocoPhillips Lubricants, the new synthetic blend oils feature strategic enhancements that go far beyond the standard industry requirements to ultimately provide the oil consuming marketplace with higher quality, premium oils at a competitive, conventional motor oil price. ... My dad ran a couple of cars over 300K on trop-artic. Of course that was in the 60's and 70's and quite a bit has changed since then.