locoluna825

Hi im new here, we have had this 91 GT 5.0 mustang convertable, automatic. The car is completly stock. Ive always noticed since weve owned it runs very cold, like no hotter than the first notch above where it rests when the car is off. NO engine light. I just recenlty stuck a new 180* thermostat in it. and it still runs cold. I dont understand why it would run so cold all the time. Is this just normal for these engines to run cold?

Also another thing ive always enjoyed is the horrible gas milage its like 14-16 MPG, when i read that alot of ppl with this year mustang get around 19-24 i kinda laughed. Which sound pretty high for an older V8 to me but ive read on other forums and ppl were actually getting that mileage on there 5.0 mustangs.

THought maybe this^ would be related to the running cold problem becuase if the engine aint hot its not burning fuel efficeintly you know.

Ive been searching online on google and on a couple of forums including this one about related problems, but couldnt find anything exactly similar to my case.

Jfsram

That's about right. 180 is usually the first notch on the gauge.
I run a 190 and that's about 2 notches from the bottom.

In a quest for mileage. Definately start off with a 190 thermostat. Then measure your highway mileage. Comparing city mileage to other Mustang involves way too many variable.

As for what numbers. Do not expect the upper range of mid to low 20's. Your combination of being a heavier, less aerodynamic and automatic are 3 strikes against mileage.

hiboostwoody

If the car is always running cold, that would account for the bad mileage. If it can't get up to what the computer considers normal operating temperature, then the fuel system will always be in open loop. Think of it as always driving with the choke paritialy on. This causes the car to run rich all the time which of course uses more fuel than it needs. You might try changing the temperature sending unit.

locoluna825

Its just that by my guess seeing that 130 is coldest and 270 is the hottest on the guage 1/2 notch would be 200 degrees and 1/4 way would be 165. which is currently now the range im running in. But before it wouldnt even go above the first mark so what was going through my mind was "dang this things cold."

So first notch is about 180 eh? well cool thats a good sign i suppose. makes me feel better hearing it form another mustang owner.

I guess I could try a 190 thermostat later and see how that turns out. I can deffenitly see that our car being a convertable its heavier and less aerodynamic makes it get less MPG's. Normally freeway driving the car gets like 16-17 MPG's, (sounds like a normal V8 to me.) but from what ive read about what some other guys were getting i was kinda thinking this thing should get more like 18-or even 19.

Im heading down to laguna today and were taking the car i wonder what the gas milage will be like...