Lower radiator hose heater won't heat anything but the hose on a 617. The thermostat design prevents thermosyponing with it closed, so the water won't move much.

Block heater is the way to go.

Failing that, a nice 100W light bulb next to the oil pan works wonders -- heat the oil and it will crank faster (I'd also use synthetic in the winter).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!