MPG way down when I turn the heat on.

[Lifted95X]

Just noticed recently that when I turn my heat on when it's cold out, my MPGs go down by 3-4. I know that it's not just because it's cold out cuz if I dont run the heat, I freeze, and get better MPG. Any ideas??

 

[Alec]

The heat also uses the AC compressor, maybe that's it? Do you lose that much mileage with the AC on?

Also do you notice a change in your coolant temp gauge?

 

[Hokie]

The AC compressor comes one when you have the defrost on

 

[Lifted95X]

the AC during the summer did absolutly nothing to my MPG. The coolant always shows pretty close to C. I have a new thermostat waiting to go in, and new coolant temp sensor. It does take a while for it to warm up. Still....baffles me to why only when the heat is on do I get really bad gas mileage.

 

[Alec]

If your truck is cold to begin with the heat may make it go below optimum operating temp.

 

[Lifted95X]

hopefully the thermostat and sensor will fix this problem. My heat does get warm, but it takes a very long time to get there, and the gauge barely moves.

 

[Hokie]

Do you let the truck warm up in the mornings? My acura got worse mpg's in the winter b/c i would let it idle and warm up each morning. Atleast, that was the only way I could justify it ~ that or they made the switch to winter gas which doesn't give you as good as mpgs (I think, oxygenated or whatever they have in colorado)

 

[Lifted95X]

always let in run for about 15mins before i leave, but, if the heat is not on, the MPG is fine.

 

[Lifted95X]

btt

 

[Stic-o]

sounds like

your stat is stuck open. The motor can never get warm enough to run good.

 

[Premier]

Yea... I have this same problem Need to fix it this weekend...

 

[have2goski]

me too

I am pretty sure my T-stat is stuck open also.

My "Check Engine" light comes on now when i get up on the highway and it is cold out.

It doesn't come on if the temp is above say 35F though.

Makes me think it is the T-stat. usually comes on after about 10-15 minutes of driving.

I think maybe the ECU allows this time for it to wram up, when it doesn't then it throws the light on.

hopefully get that taken care in the next week or two

 

[Opera House]

Don't think it gives a code for being cold

Mine was stuck open on my 97 and never got a code when it was cold. It will give a code if the wires to it open or they short together. I'd unplug it and put it back together to clean any corrosion. There are two. One for the gauge and one for the computer. Code may be unrelated to temperature.

 

[have2goski]

guess i should get the codes pulled an see what they are telling me

 

[Premier]

I just replaced mine this weekend... Damn its nice to have heat that can melt you LoL.

It turns out that my thermostat wasnt stuck open... When I pulled it out I found that someone put a 92 degree one in. Yup thats right 92 degree. Couldnt freakin believe it...

 

[Den85GT]

i did mine also

it was kind of a pain but will be worth it when it gets cold again 40 degrees now, but wait it will be 0 before you know it

 

[jjue]

Or, your thermostat could have "blown up" or corroded itself apart like mine, acting like a stuck-open thermostat. My thermostat

 

[RickOTR]

never let your Explorer idle for that long. It will cause the o2 sensors to go rich and ruin them. I had to have the dealer replace mine at 30000 miles because I let it idle and warm up in hte winter. Glad it was still covered under warranty.