Second odometer for WVO tank?

[Jetta90GL]

I have been looking for a simple way to add a second odometer on my 90 VW Jetta. The idea is to have it start counting miles anytime the WVO selector switch is turned on. One problem is the original VW speedometer is mechanical, so I thought maybe something like a sensor on an axle or wheel? Any ideas?

[Jetta90GL]

I did some searching and found this:
http://www.spatechnique.com/product_...eedometers.asp
It looks like it uses a simple magnetic pick up, hopefully off of the wheel. I am going to hook its power to my WVO solenoid power so that it only tracks WVO burning miles.

[Wazabi Owner]

Good for you if you have a 90 A2 Jetta and the OEM odometer works in the first place. Sounds like a neat idea. Chime back in and mention how it works as I'm curious. I consider my WVO an additive to the diesel, even though it seems to use much more WVO than diesel.