Engine overheated - now have poor gas mileage

[MNGator]

About three weeks ago my 2012 Dodge Journey AWD SXT overheated while driving home. As I still had about 50 miles to go, I stopped at a service station to see if they could determine if anything was wrong. The garage removed the thermostat as a precautionary measure until I could take it into the dealer.

Once I took it to the dealer they found a hole in the thermostat housing (they told me someone drilled a hole in the housing. Looking at the housing, it was not a drilled hole, rather looks like excessive heat caused a blowout. Once they replaced the thermostat housing and the thermostat, they told me they tested the vehicle extensively and it was all okay. Sounds great, $225 for a thermostat housing and thermostat notwithstanding.

As I drove the vehicle home, I noticed it wasn't quite overheating, but was still running hotter than normal. As I looked at the service record, their extensive testing involved driving the car for a total of 6 miles. Glad they were thorough! I have now been driving it a couple of weeks, including a 1,000 mile trip last week. The temp gauge never went to the halfway mark before, but is now routinely slightly above the halfway point. If I am doing stop and go in rush hour the temps get above 212, highway driving is between 195 and 205. I didn't check it all that often before, but if I recall it was typically between 185 and 195.

My concern at this point is in addition to it running slightly hotter than normal, my gas mileage has decreased as well. Where I used to get 24mpg on the highway, I am not at 20 and am at 16-17 in the city. Any ideas on what may be happening? I called the dealer and they told me the temperature ranges are normal, but didn't have any explanation for the gas mileage other than to say that is typical for the DJ.

[MNGator]

Thanks 11 - I will give it more time. I do mostly highway driving and even though this car is only 41 months old, I already have 94,000 miles on it (mostly highway). If there is something wrong, I just hope it manifests itself in the next 6,000 miles before the powertrain warranty expires.

[dhh3]

My temp gage has always pointed slightly below 1/2 since new. I don't know the actual temperature because I have never looked at it. I keep my center screen on fuel economy and reset it every time I fill it up. I very rarely drive the interstate but if there are no lights I can get up to 21; a lot of lights and it can drop to 14 - 15. Bought it new not quite one year ago.

Edited May 26, 2015 by dhh3

[Woah322]

As long as it don't go above 230.240 it's normal

[bramfrank]

The first and most important thing is to figure out WHY it overheated in the first place, because it shouldn't have. And then you need to verify the radiator and heater cores aren't blocked and to get the cooling system properly pressure tested.

[MNGator]

Thanks all. The dealer did test the pressure once the housing was replaced and said it was normal. I have tested the old thermostat in a pot of hot water and it seems to be working, opening at about 185. I am concerned that there are other issues, but not sure what to check.

I am very concerned at the condition of the old thermostat housing, the white discoloration and the blow through indicating very hot high pressure build up. In any case, pit side of a loss in mpg and running slightly hotter than before, everything seems to be working. I have put over 2,000 miles on it since the repair and am still at 20 mpg on the highway, down from 24. Time will tell I guess.