this forum is loaded with people that will tell you that
circulating coolant through the tank is the way to go...
but the truth is that it takes forever for a diesel to warm up and
especially on a cold day... i have started my diesel, and driven completely
home and not felt one bit of warm air through the heater..

So if it was fueled with svo then i would have never gotten it started...

So you tank must be metal...
1. place a 12v bartery warmer under the tank...
or even a block warmer... install a plug in coolant warmer..
install an electric dipstick... and keep your car in a heated garage..
you may even be able to rig some type of aquiram warmer in the
tank..
2. Also circulate coolant from the engine through the tank and back to the
radiator....
3. change your thermostate.

4. you may want to buy an electric water pipe warmer and wrap it around your svo tank and plug it in at night.....