I have a Propex propane in my Westy and it doesn't do the job below 10F or so. To be honest, it is fine for camping for ski trips, but I live in my van part time, working 180 miles from home. I need to sleep well, wake up and go to work. I'm not interested in staying warm enough to survive. I want to wear shorts in my second home when it is zero degrees F outside. So I went with an Espar D2 in my Sportsmobile and loved that and did it again in my Transit. I went with the diesel model D2 over the gas version (B4?) because gasoline is more volatile than diesel. I'm sure the gasoline model works just fine and would sure make things easier since you could just pick up from the factory gas tank. The other thing about choosing diesel is that it also allowed me to use a diesel cooktop - Webasto X100.