I have been using Klotz fuel and oil this year and seem to be the only one that I know of that is. The KL-491 seems to be pretty close to the VP U4.2. I was just wondering peoples opinions, any experiences good or bad. Here is a link to the klotz site which has a tech sheet and msds sheet. http://www.klotzlube.com/storeProdDetails.asp?pi=38