One block heater or two?

[Daox]

You can do that, but remember that once up to temperature that surface is used to cool the engine too. So, if you do it you will require your radiator to do more cooling.

[ConnClark]

Where is this block heater supposed to be installed? You mentioned a plugged hole. If these holes are the soft plug holes you do not want to install a block heater in both of them as they are there to prevent your block from cracking if the coolant does freeze in the block.

[GeneralAnarchy]

I think a good secondary heater would be the magnetic type. I still have one I used on my old pickup truck before I bought a Prius and now get 5x the MPG. Now I laugh when I drive by the gas station. But where on the Prius engine block is it optimal to stick a magnetic heater? The oil pan seems good, but crawling under and taking it off every winter morning would get old.

[comptiger5000]

They do make stick on oil pan heaters that aren't magnetic and are intended for permanent installation.

[fidalgoman]

Originally Posted by RobertSmalls

There is always the coolant circulating type: Amazon.com: Kat's 13100 1000 Watt Alumininum Circulating Tank…

I've put block heaters in about a dozen of my cars over the years and the circulating tank heater was far superior in every way. Unfortunately some of my favorite HF cars would not accept them so I went with multiple freeze plug types. If yours can accept this type they circulate through the heater circuit which has the bonus of not only a very warmed up engine in about 45 minutes but instant hot air on the windshield at startup.

I think the reason some cars can't use this type is that it sits too high and the heat doesn't want to rise through the engine since it's already near the top of the coolant flow. I don't remember the brand name off the top of my head but my favorite one had a little very lightly loaded check valve system and just sort of peculated the hot water through the engine. The other issue is some heater systems have a flow valve for the coolant whereas most are full pass and mix cool and hot air for cabin temp.

Economy is not just about FE, it's about the car lasting longer as well. A pre-warmed engine can go a long way even if you don't live in the great white north. Something I'm thinking of installing as well is a pre-oiler to lubricate the bearings before engine startup since most of your engine wear is 'supposed' to occure at this time.

[Piwoslaw]

Thanks ConnClark. I guess that if at least one freeze plug should be left then I already know how many block heaters to use.