Several other board members have posted about how their use of "mixed fleet" oils has visually reduced their engine deposits, and you can safely make the switch permamently if you choose. Most of the mixed fleet lubes have "SL" certs, so by definition they conform to whatever SH, SJ, or SL API rating your owner's manual may recommend. The Shell Rotella spec sheet sums it up: "Exceeds requirements of today's high performance, fuel efficient, low-emission diesel and gasoline engines while providing excellent performance in older engines..." The Motorcraft diesel lube at WalMart is the least expensive version I know of. The one issue is that they're commonly available in 15w-40 weight, which would only be desirable in warmer months in the Bay area. A Napa Auto store or truck supply may carry a lighter weight of diesel lube for the winter months. Your oil consumption is awesome -- about the same as my BMW when it had only 50,000 miles.