The GreaseCar modification to my car doesn't change anything with the engine - it's a 2nd fuel tank that's heated from the waste heat of the engine (coolant).
The GreaseCar website has an excellent flash animation explaining everything.
Here's what the modification looked like once I got it back from Young Street Garage.
1) Under the hood.
The red hoses contain coolant to heat up the fuel filter assembly on the right. At the bottom, you see the two solenoids to switch diesel/veggie/diesel-backflush. You can see the VW engine cover is still there, I eventually remove it.
2) The dashboard.
An aluminium plate holding the fuel gauge and 3-way illuminated rocker switch is attached quite snugly to the bottom of the standard centre dash. Below, the ash tray is removed (we don't smoke) and the GreaseCar temperature gauge is installed.
3) In the trunk.
The spare wheel is removed, and we now carry cans of RideFlat wheel sealant in our emergency kit. I've tried to insulate the tank with foil bubble wrap. Fiberglass would just get nasty and loses its insulating properties if compressed. Notice how we don't lose any trunk space with the modification. I suggest using a end of a roll of masking tape to protect the fuel-level leads from weight of trunk items (hidden by a block of white foam in the picture below).
I found the heat of the oil to suffer in the winter. So after reading InfoPop a lot, two upgrades that should solve my problems of winter vegoil fuel heating were discovered.
1) Brazed Plate Heat Exchanger
Click to animate.
Brazed plates have more surface area than flat plates, so they can transfer heat from the coolant to the vegoil fuel better. This is the "heavy lifter" for vegoil temp. The thermal energy transferred is much greater than the GreaseCar thermal filter assembly or the PlantDrive VegTherm. But it is limited by how hot the coolant is.
The engine cover doesn't fit anymore with all the extra hoses. I didn't like it anyways.
2) PlantDrive.ca's VegTherm Mega
30cm long, 32Amp at 12V of electrical resistance heating. This sucker burns skin on contact. After the oil is heated in the trunk tank, after it's insulated in the hose-in-hose line under the car, after it's warmed up a bit by the GreaseCar thermal filter assembly, after it's raised to the same temp as the coolant by the BPHE - the VegThermMega does it's thing.
I also stopped using foil bubble wrap for insulation and moved to copper pipe foamies - they insulate way better.
As you can see, things are getting very tight. But it's still manageable, even for me.
Yesterday, my BFHE was showing temperatures of 50C (it was likely warmer, temperature sensor heat loss to ambient air temp) I turned on the VegTherm and the oil temp out the other side was 68C.
Time will tell how it does in -30C.