For 12 miles at 37, you may never warm the car up to get decent mileage. Not sure why your MPG is so bad. I am averaging close to 24 MPG everywhere and that is in a car that is over 500 lbs more than your CX-5 (with the same engine).
I doubted your statement that the car would not warm up during a 12 mile drive, but I now think you may be right.
The other day I set the Fuel Economy Monitor to briefly display when the ignition is turned off; in other words, every time I turn off the car, the mileage for that trip is automatically shown.
I just got back from shopping. It's 8.1 miles one way. The air temp was 47°.
>My mileage there from a cold start was 19.
>My mileage back after being warmed up was 26.
>The only variable is that the drive there is 76' in elevation higher than my point of departure (so the ride back is a 76' decline).
>>Over an 8 mile drive, that's about 10' per mile...certainly not enough to affect mileage.
I don't know if the mileage difference is that great in the summer, but 47° is not cold enough to materially increase the amount of time it takes the car to warm up.
Maybe there's other stuff going on with the car where other settings from other inputs are causing this. But I'm really inclined to believe that (as you say) 8-12 miles is a "short trip" where mileage grossly suffers because the car is not warmed up.
That 12 mile trip to church we discussed is confirmation of this. It's only 40' higher in elevation than my home. Low mileage on the cold drive there/better mileage on the warmed-up (had not cooled off) trip back home.
It's also further confirmed by a trip I took to a party in early January. 80 miles @ 55MPH round trip with 4 of us in the car, and my seat-of-the-pants (un-monitored) guess at mileage is 27 or 28 based upon how much Trip A mileage went up. I kept wondering if there was a difference in road surfaces or what??? Maybe you found the answer.
The other variable (as others have said) is speed. All my local trips are non-stop (no traffic) 45-55MPH. The only longer trips I've taken besides that party have been on the 70-80MPH interstate, and my mileage sucked on those trips.
Now I can't wait for it to get warmer so I can verify this!
ps: I checked elevation because this area is so roller coaster that it's deceiving. I would have sworn that my 12 mile trip to church was mostly uphill all the way and that's what accounted for the mileage difference. It nets out to 40'. I am shocked.