Does running the heater decrease gas mileage?

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... :confused:

that doesn't even make any sense.

what? :screwy:

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.

Sure they aren't thinking of the AC?

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

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.

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... :confused:

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.

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

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.

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

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.

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.

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.

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

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.

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.

well just to cool things off a bit, im not tryin to pick any fights or get anybody ruffled up, i realize there are different configs. mine is a 02 2.2l s10 and the heatercore is in the center of the HVAC box well away from the evaporator. and i know on mine there isnt one and ive seen quite a few like mine with 2.2s. the 4.3s im not 100% on because i havent had to do much to the HVAC on those but i do know they have the bypass off of the waterpump.

The thing is, running the heater when you ar trying to heat the engine up will only result in more fuel burned.

The colder the engine, the more fuel used.

During road use after it has warmed up I can't see a huge problem or difference in economy but I know I am going to be blocking my rad off a bit this winter to help keeps things warmer.

well just to cool things off a bit, im not tryin to pick any fights or get anybody ruffled up, i realize there are different configs. mine is a 02 2.2l s10 and the heatercore is in the center of the HVAC box well away from the evaporator. and i know on mine there isnt one and ive seen quite a few like mine with 2.2s. the 4.3s im not 100% on because i havent had to do much to the HVAC on those but i do know they have the bypass off of the waterpump.
im not in a heated discussion, didnt think i was anywase, just an argument... you claim you dont have a water valve, its not that big of a deal, but what i am saying, as a payed machanic, is that all the vehicals i have delt with have them in them, things change from year to year and model to model, im not positive unless i open up the mitchel (like a chitlens, but with 5x the amount of info and 10x as accurate, and 3x the cost) and find it in the locater

Is the valve integral tothe core?
Is it cable or vac controlled?
Do they have them on 98 S-10's?

Thanks for your replies. No, they never said why it drinks more gas using the heater, only that running the heater used more gas. I have never noticed a difference in gas mileage running the heater.

But I know the defrost does run the A/C (wonder why :confused: ), and I also know not to turn on the heat when letting the engine idle; I don't turn on my heater until the needle on my thermometer starts going up.

It uses the AC system to dehumidify the air.

Also, don't use the heat until the engine is warmed up and at normal operating temperature. This can save some serious money through a year seeing that when cold, the engine will really drink the fuel.

Yes. Also, even in the summer, I always let the engine warm up for at least 30 seconds, because driving off without letting it warm up really plays hell on it, especially in winter. (In winter, I let it warm up for about 2 minutes or more.)

best rule is one minute in the summer, 3 minutes in the winter and maybe 5 minutes if it is really cold out.

well i wouldnt move a vehicle till the temp gauge reads at least one tick past cold. i really doubt letting the heater run on low when its warming up is going to slow it down any. this would make a good test. see how much the heatercore actually can drop the temp of coolant. i dont think it will drop the temp dramatically, maybe 10-15F on full blast.

best rule is one minute in the summer, 3 minutes in the winter and maybe 5 minutes if it is really cold out.
but, cold to my american ass isn't but chilly to you kanucks... and the water valve on your dime i beleve is vac actuated, and it shouldnt be integrated, dont know, think its in the dash, mines bad on my 98, wont quit pouren heat out, bad in augest, but i havnt fixed it, found it easyer to get a 5/8 ball check valve and shut the core off manualy

found it easyer to get a 5/8 ball check valve and shut the core off manualy

I've seen a few people do this, and it works good. It's a cheap fix, and it's always easy to turn the water on and off

easy, yes, pain in the ass, defenetly, warm days, cool nights, so i stop just to get heat in the truck, and the body shop broke my hood latch and ive yet to fix it (ordered the part, fixen cable when there is a 4.3l missing from the bay) and it now takes a pair of plyers to open the hood

DM this gives you the perfect opprtunity to do the first mod that I'm planing for the spring.

Install a Vega hood hinge kit and have the hood opening towards the front. I havn't really looked into it, but it might be possible without any real body mods

I know that it's a completely useless idea, but it's something different

DM this gives you the perfect opprtunity to do the first mod that I'm planing for the spring.

Install a Vega hood hinge kit and have the hood opening towards the front. I havn't really looked into it, but it might be possible without any real body mods

I know that it's a completely useless idea, but it's something different
useless, yes, makes it more of a pain in the ass to work on, yes, but, damn it looks good lol
been thinking about doing a drop foward hood, as long as its attached to a 2nd gen cowl hood :p

Running the heater in defrost mode can decrease your mileage, because to keep humidity out of the air, the defrost mode actually turns on your air conditioning -- helps the windows clear faster.

eti engineer