Using the heat when it's cold... mpg drain?

[newhavenpatriot]

The title says it all... I know AC is a huge drain on mileage, but does using the heat work the same way? I'm admittedly clueless when it comes to cars; I just bring it to the oil change place every 3,000 miles and have them do what's in the Toyota maintenance booklet once I hit a maintenance interval.

[Frank Lee]

The heater doesn't activate the a/c compressor, which is the big power drainer. Using the heat setting especially with low fan settings should minimally impact fe- probably at an undetectable level.

I tend to like to regulate temps with the heat control on the lowest blower setting. I know some people, particularly women, like to blast that freekin fan wide open at every opportunity. The fan draws juice which must be generated, indirectly, by the engine.

There has been debate about whether it's better to leave the heat control on cold until the car warms up, or put the heat control on hot right away. Conclusion is that if the blower fan isn't causing the mass extraction of heat from the heater core, the difference is so minor as to be inconsequential. I leave the control on hot right off, with blower off, on the defrost setting, and wait until I can feel some warmth trickling out with my bare hand before bumping up the fan setting a notch or two.

All that breathing tends to fog things up so it helps to either have the window cracked open a bit or only close the door to first catch until the heat starts flowing.

Re: using the defroster: the defrost setting will activate that a/c compressor on most cars so that could be a similar loss to using a/c. But when you need it, you need it.

It helps to clear snow from the air inlet at the cowl- reduces moisture and thus fogging on the windshield. On that note, stomping the snow off your boots and shaking the floormats clean can help reduce humidity in the car too.

The gung-ho can disconnect the a/c clutch for compressor-less defrost operation. I guess I'm gung-ho as all my cars are like that. Well, really it's because the a/c is broken on all of them. That eliminates compressor operational losses. I still haven't bypassed the comps with shorter belts.

And... unless you really, seriously do fall under the severe service guidelines, you are wasting oil and money by changing it that often. It should be able to go more than twice that far between changes.

[PaleMelanesian]

With a full grille block on a hot summer day, just moving the temperature control dial to Hot will measurably drop the coolant temperature. This is with the fan turned OFF. Based on that, I conclude that it cools the engine even with no fan blowing, so I leave it on Cold until it's fully warmed up.

With a 10 mile commute, a tiny aluminum engine, and heavy use of EOC, that's pretty much never. I practice dwg (driving with gloves).

[moorecomp]

I guess I am one of the "hard core" also as I have disconnected my a/c compressor electrical connector. I like to run my defroster or the setting where the air comes out of the defroster and at floor level. What I did not know was the radiator cooling fan comes on whenever the a/c is supposed to come on. I noticed at night how my lights would dim slightly and you could feel the load on the engine whenever you selected the defroster. The rad fan fuse is 40 amps! I looked in the wiring diagram for my car and found that by pulling the a/c fuse (15 amp) the fan no longer kicks on when I select defrost. You may want to check yours.

[DonR]

Personally I hate that feature. If they give you a button to turn on the a/c when ever I want, they shouldn't feel the need to have it come on automatically. Maybe on 100% defrost only.

In my Mitsubishi I can turn the knob a few clicks past heater toward heater/defrost before the A/C will activate. I figure it's cheaper to run the fan faster than the a/c compressor. I was able to figure this out by turning on the reciculator feature & turned the selector knob until the recirculate light went out. On defrost it won't let me have the recirculate on, to try to get rid of the humidity.

Don

[newhavenpatriot]

Well, I do have an AC button... if I leave that turned off, would the compressor still activate with the defroster on? I don't see why the AC compressor would need to be on for the defroster to work, given that it's called an AC compressor, but then again, I don't even know what its function is.

[moorecomp]

It acts as a dehumidifier to aid in defogging the windshield. The a/c button allows you to turn it on when "You" want. The car will turn it on when "It" wants to.

[orange4boy]

In the winter here it gets pretty humid so every once in a while I put my dehumidifier in the van to get the accumulated moisture out. That way I don't have to use the fan as much.

You can have a block heater or coolant heater installed that plugs into a 110V outlet that warms up the engine. With a timer you can set it to warm up the car before you get up in the morning so you have instant heat. This is good for FE as well because the engine gets up to operating temperature much quicker. I have one that I use year round because I have a short commute.

[newhavenpatriot]

Okay, so when it gets cold out and you get in the car and the windshield is all fogged up, the only way to get the condensation to go away is to run the defroster and heat, right? Just trying to find out if there's a way I can do this without killing my FE. (I had to run the defroster and heat for an hour tonight cause it actually snowed here... that never happens in October!)

[Frank Lee]

I've been known to wipe it with a rag too. There are "anti-fog" wipes and cleaners but I haven't tried them.