Does running the heater decrease gas mileage?

[Ducaire]

For the longest time, I thought that running the heater only used heat from the engine, and it did not effect the gas mileage. But there are strange folk who swear that running the heater drinks their gas faster...

[dimefury]

that doesn't even make any sense.

what?

have these "strange folk" explained why they think the heater uses gas?

i am having a really hard time trying to figure out why someone would think that.....it doesn't make any sense. do these "strange folk" understand how a automoblie's heating/cooling systems work?

the heat inside your car comes from the heater core, which is basically a small radiator inside the passenger compartment. the heater core is warmed by having engine coolant run through it. the heat is blown off the heater core with an electric fan. no part of this uses more gas.

no, running the heater does not use more gas.

[movin2stereo]

Sure they aren't thinking of the AC?

[dmbrisket 51]

can... if the core is plugged, and there is a water valve to shut it off when not in use, then the extra load could decrease the gas mileage by possibly a mile to the gallon or less

[OverBoardProject]

In the old VW's with the gas powered heaters they would affect the mileage, but I never noticed when I had my old van.

I can't see a car using any more.

Winter gas is often worst quality than summer fuel with antifreeze added to it, so if your getting worst mileage this might explain it Ducaire. Ask your local filling station about how their gas differes from summer to winter.

[Crasen]

Originally Posted by Ducaire

For the longest time, I thought that running the heater only used heat from the engine, and it did not effect the gas mileage. But there are strange folk who swear that running the heater drinks their gas faster...

they might be mistakingly talking about the defroster. If you use the defroster you will actually get a lower gas mileage, some heat/ ac control panels only let you select a/c, vent, and defrost. they could be putting it on defrost thinking it is the heater. When you use your defroster the a/c system will run. It will send the air through the evaporator to remove moisture from the air. Dry air doesn't tend to fog up your windows like moist air does.

[unbe]

I disagree with brisket,
a)there is no different load between a shut valve and a plugged core
b)even if there was your water pump is non-positive displacement and wouldnt require more torque if it was deadheaded

[BlazerLT]

It will make your fuel economy suffer a bit.

It isn't because of anything mechanical, it is just because the heater core will cool the coolant even more which is picked up by the coolant temperature sensor for the computer which will richen the misture a bit.

This is why you NEVER run your heater until the engine is up to temperature.

When you are running your heater, you are technically using the heater core as an internal rad which will double the time for your eninge to warm up.

Leave the temp adjustment to full cold and everything off until it is up to temperature and then turn it on.

It will save a lot of fuel.

[unbe]

Yea but isnt it nice to jump into a truck thats nice and warm and the windows are defrosted?

[BlazerLT]

Originally Posted by unbe

Yea but isnt it nice to jump into a truck thats nice and warm and the windows are defrosted?

Not when you just wasted gas letting your truck sitting their idling for more than it needs to.

[RahX]

the heatercore is part of the thermostat-shut circulation it actually warms your engine up a lot more evenly and it doesnt matter if you dont have a shutoff valve on it, it circulates all the time. you have a flapper door in your hvac box that closes off the heatercore airflow and the air goes a different route. if you put a shutoff valve on there and shut it down, i dont imagine it causing problems. heating the coolant in the block first then dumping cold coolant in there might cause some wackyness for a min or two but nothing to get flustered about. so run the heat whenever you want.

[BlazerLT]

Originally Posted by RahX

the heatercore is part of the thermostat-shut circulation it actually warms your engine up a lot more evenly and it doesnt matter if you dont have a shutoff valve on it, it circulates all the time. you have a flapper door in your hvac box that closes off the heatercore airflow and the air goes a different route. if you put a shutoff valve on there and shut it down, i dont imagine it causing problems. heating the coolant in the block first then dumping cold coolant in there might cause some wackyness for a min or two but nothing to get flustered about. so run the heat whenever you want.

Warms your engine more evenly? There isn't such a thing as evenly warming an engine, it ain't a weiner over an open fire.

If you have the heater on your will be cooling the coolant that is trying to wam up. The heater core is essentially a small radiator and you removeing heat from it to heat the cab only slows the engine warming up.

The trick to getting your engine running as fuel efficient as possible is to get your engine hot and in closed loop as soon as possible.

The longer it is cold, the longer it will be choking down more fuel to warm up.

[dmbrisket 51]

Originally Posted by RahX

the heatercore is part of the thermostat-shut circulation it actually warms your engine up a lot more evenly and it doesnt matter if you dont have a shutoff valve on it, it circulates all the time. you have a flapper door in your hvac box that closes off the heatercore airflow and the air goes a different route. if you put a shutoff valve on there and shut it down, i dont imagine it causing problems. heating the coolant in the block first then dumping cold coolant in there might cause some wackyness for a min or two but nothing to get flustered about. so run the heat whenever you want.

interesting... so what your saying is that there is alwase water/coolent moving through the heater core? WRONG. there is a shutoff valve. The put the evap for the ac right in front of the heater core, if there was alwase HOT inside of it, the a/c would be mediocor at best, the cores flow is shut down when not in use

[RahX]

ya ever looked at the inside of a HVAC box? there is a door that mixes the incoming air. it can be anywhere from cold to totally hot. what does it do? when its in the cold position it blocks the air from flowing through the heatercore. when its set to any other temperature that door drops down and can be anywhere from almost totally blocking off the heatercore to allowing almost total airflow through the heatercore. and as far as i can tell my 2.2l s-10 has no heater core block off valve to block coolant flow to the heatercore. the coolant circulates coolant from the radiator and the block around so there isnt one spot that gets warmer than any other spot, so on warm up it does help warm the coolant and block evenly. i dont know if it makes a diff with automatic heater controls or not but i know for sure mine with manual controls does not have one. and as for decreasing gas mileage, anything it does until the truck warms up is pretty negligible IMO.

[dmbrisket 51]

ever take the dash out of one of these? I do it atleast 3 times a month in the winter, the heater core and evaporator for the A/C are stacked on top of each other, the controls of today dont work on a simple cable control they once did, there is a water shutoff valve to the heater core, it is a huge problem child on some vehicals (not ours, ours are a real bitch to get to) change dozens of them in the summer months when the heat doesn't shut off and or the ac shop cant get the ac worken right.