I managed about 1200 miles before changing. You probably only have to do it 2-3 times while the fuel system is cleaned by the veggie oil then as normal after that. You'll start to get the symptoms of a blocked filter, lumpy acceleration, can't get full power etc which will give you a warning that it is due a change. It's good to keep a spare in the car just in case you have a lot of muck in your tank. I needed a tow once cos there was that much slime/muck in my tank it blocked the fuel line from the tank - didn't even gat as far as the filter. This was easy to rectify (about 1 1/2 hours work) and as far as I can tell not very common.
One thing I didn't mention is to keep an eye on your oil level cos if the veggie gets past the pistons into the sump it won't evaporate like diesel does. If the level starts to rise or the oil gets thick and sticky change your oil. I check my oil level and condition weekly as a matter of course anyway. In extreme cases where this has been ignored for a period of time the oil has been know to become almost solid. I have never had a problem with this.
I'm now investigating injection timing and injection pressures to find an optimum for running on veggie oil. I'll keep thisthread posted with anything I find.
One thing I didn't mention is to keep an eye on your oil level cos if the veggie gets past the pistons into the sump it won't evaporate like diesel does. If the level starts to rise or the oil gets thick and sticky change your oil. I check my oil level and condition weekly as a matter of course anyway. In extreme cases where this has been ignored for a period of time the oil has been know to become almost solid. I have never had a problem with this.
I'm now investigating injection timing and injection pressures to find an optimum for running on veggie oil. I'll keep thisthread posted with anything I find.