Rotella T 15 W 40 costs about $9.00 a gallon at Wally Mart. I am running it in the Suzuki 650 thumper. I can't say it's creating any bad results. I don't see it running low as fast as when I was using Suziki oil that cost almost $4.00 a quart. This engine was designed about 20 yeaRS ago, when oil was mostly yak fat rendered in a cast iron pot in a Voo Doo masters back yard. The RE is an old design, too. I expect the metalurgy has improved over the years & with the modern oils & improved manufacturing processes, the longevity will be improved, even IF we dont run in circles fretting over Which is the BEST slickum for my Baaabeeee. IF I was gonna go hog wild I would look closely at Royal Purple. The testimony from the guy who installed the satellite internet was, he put it in his crankcase, tranny & differential on his Biggo Dodge Ram & picked up 2 MPG. The only way it can increase MPG is to decrease friction & with decreased friction, decreased wear follows suit. Now, the question is, with the added expense of the Super Slickums out there & the riding we do, will we ever recoup the costs of the oil in avoided maintenace?