How bad is using cabin heat

[RandomFact314]

We all know that A/C is a no-no, what about using the heater? Its really cold 85% of the time where I live and I don't know if I should be using the heat so much...

[Frank Lee]

I can't imagine just having the heater on hot w/o the blower causes any measureable fe changes. I'd think if there's an fe penalty to heater use it would be directly related to the juice the blower draws. You can thus calculate fe/hp/wattage use estimates.

[PaleMelanesian]

I have measured a slowdown in the warmup time by having the temperature set on hot, even with the blower off. You want the engine to warm up as fast as possible, because a cold engine guzzles much more fuel. see below

Once the car is warm, I don't think it makes a difference, other than the power draw for the fan.

Mini-experiment: cold start fuel consumption and warm-up time - MetroMPG.com

[Frank Lee]

Thanks, I wasn't thinking of during cold-startup.

[RobertSmalls]

Most cars are equipped with a valve that keeps coolant from flowing through the heater core when the heater is set to "cold".

In the winter, I start with the heater at "cold", then wait for the ScanGauge to show >190°F. Then I set the heater to "hot", and the coolant temperature falls ~20-30°F. I wait for the temperature to recover, then I turn on the blower to heat the cabin.

If it's really cold 10.5 months out of the year (in South Carolina?), you should get a block heater.

[roflwaffle]

Originally Posted by PaleMelanesian

I have measured a slowdown in the warmup time by having the temperature set on hot, even with the blower off.

How much of a slowdown?

[jesimpki]

I agree, a block heater helps tremendously, year round. I'm running mine 2-2.5 hours now and I have warm air after I pull out on the road and drive less than a quarter mile (I have to give the thermostat time to open). Shifts are smooth with lower idle speeds and I get overdrive sooner.

[jamesqf]

You could also try a partial radiator block to help it warm up faster, and maintain operating (and good heating) temps.

I don't know if this is true of all cars, but on a long downhill my Insight cools to about 140 F, as the fuel to the injectors is cut. When it drops below 140, it starts burning extra fuel to keep the temp up. I seem to see much the same behavior in the pickup, but since it's pre-OBDI, I only have a rough idea of the actual engine temp.

[Thymeclock]

Originally Posted by RobertSmalls

Most cars are equipped with a valve that keeps coolant from flowing through the heater core when the heater is set to "cold".

In the winter, I start with the heater at "cold", then wait for the ScanGauge to show >190°F. Then I set the heater to "hot", and the coolant temperature falls ~20-30°F. I wait for the temperature to recover, then I turn on the blower to heat the cabin.

If it's really cold 10.5 months out of the year (in South Carolina?), you should get a block heater.

190 degrees? Man, you must have anti-freeze in your veins!


I'm on Long Island and in winter I'm freezin' my butt off! I put the heater on at around 150 - even slight heat is better than no heat!

[MetroMPG]

Another option let's not forget (if you want a toasty cabin ) is a small space heater working away for about 15 minutes in tandem with the block/coolant heater.

I'm used to this concept because of the ForkenSwift (no combustion or resistive heat). But truth is, I've done it for years in my ICE cars.

I'm always surprised how much more fuel I waste *as a driver* when I'm cold, than when I'm warm and happy.