Important Breakthru In Fuel Efficiency!

[CTScott]

Originally Posted by bronsin

I have installed a block heater in my yaris and am currently experimenting with it. My drive to work is 6.7 miles so about a mile or three of that the engine is not up to temp. I get 32-34 mpg in summer but less than 30 in winter. So Im hoping the block heater will make things better.

So Ive had frost on the window and have to run the defrost at full blast. The cool light isnt going off for a mile or more in spite of the heater.

Im thinking "that fan is cooling the coolant and defeating the heater"

So I put plastic over the window last night so I wouldnt need the defroster.

This morning the cool lite went out after a block!

So you really dont want to use the cars heater to keep the coolant from cooling down and the engine from burning more gas.

At least on sub 10 mile trips.

When you go into defroster mode the AC compressor automatically runs, and when that runs the radiator fan automatically runs, so you are definitely correct that defrosting delays getting the engine warmed up.

If you do the mod to unlink the automatic AC with defroster, you will still be able to use the heat to clear the windshield, without causing the radiator fan to run.