If you are really desparate you can light a fire under your car. I have done it before, it works. THe first time I did it I worried that I would set the car on fire, but it did not get anywhere near hot enough - I guess the engine works like a big heat sink, the heat just moves to the cold(er) part of the engine. Here's what I did:
salvation army frying pan and a coffee can inside it. poke a bunch of holes around the bottom of the coffee can and then light 7 or so charcoal briquettes inside the coffee can. Slide it under the car and come back in an hour.
I would only do this if you don't have anyplace to plug it in. If you can plug it in, get a magnetic heater and stick it on the oil pan, or consider spending $50 on an adhesive oil pan heater - I have used them they work about as well as a block heater. andy (minnesota)

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andy t
'78 300d
'95 volvo 850, wagon
'86 300sdl - engine out, maybe I'll have it rolling by June

whole bunch o' bicycles