Block Heater Basics

Almost every block heater I've seen just heats part of the motor. They usually fit into a frost plug in the block. If you have really severe winters, and your heater core plumbing supports it, one of those circulating heaters works wonders.

I have a 1,000 watt Temro coolant heater from Canadian Tire on my old Ford F-150. The old one was 10 years old and the new one this fall cost $50. It's plumbed into the heater core hose, and since that old truck has a simple valve to regulate the heat, you just leave it on Max all the time.

It uses a thermosyphon effect to heat up a bit of coolant, which expands slightly in the heater chamber, and push it through the heater core. A check valve closes and the cycle continues as long as you leave it plugged in.

Not only do you heat the entire block, but the heater core as well. When you start, the defroster can blow warm air immediately.

You can't use a coolant heater like that on any car with a vacuum or electric coolant valve. Once you shut the motor off, the heater core valve closes and the circulation heater wouldn't work. I suppose you could rig up some sort of bypass with check valves, but what a PITA.

Even with a frost plug heater, some heat will reach the oil pan - eventually. If you're worried about cold, thick oil, run a synthetic in winter. A 0W-30 is best, if not available a synthetic 5W-30 then.

Most HD truck engines here in Canada have an oil pan heater as standard or optional. If I was forced to live in a climate that routinely got colder than -45, I would have an oil pan heater as well.

 

Here's a link to another tread on block heaters in the Prius.
http://priuschat.com/forums/mpg-results-of...esults+one+tank