I use SunWizard's design and have three 3way valves mounted on the floor board. I like the simplistic design and it has been trouble free for 4000 miles now. I've noticed lately a change in the way the filter valve was operating. It seemed harder to turn one day then easier the next. It also stopped having the auditable click when swithing filters. Yesterday it failed on me when I switched over to WVO and must have stuck in between the normally closed port and the normally open port. Luckily I was only 30 miles from home and the tow wasn't to outragious.
Once home, I pulled te valve and bypassed it with a piece of 3/8 alum. tubbing. Dismantled the valve and found the valve stem had pulled out of the nylon ball valve. The top of the nylon ball had broke which alowed the stem to move out of the seating area.
I'll post some pics so you guys using these valves can get an idea of what I'm talking about. I just wanted to give other grease burner warning of possible failure on these valves. I'm hoping it's just a one time occurance and plan on replacing it with the same design.