Sudden decrease in MPG

Cooler weather is your enemy in this situation, if you don;t have one a block heater might help, also there are several posts on grill blocking you might look into.

 

Any chance your destination was at a lower altitude than your home? If so, that could easily explain the difference.

I've noticed cumulative mpg during a trip often peaks while I'm crossing rivers en route to wherever. That's no coincidence.

 

welcome! are you measuring by the tank full, or watching the display?

 

With colder temperatures, your tires could be under inflated?

 

the display is almost useless, too much variation. if you are truly concerned, track your tanks and manual calculate the mpg's each time. report back here, and if it looks significant, we can start giving you some things to have checked. many people have been fooled by the 'instant mpg meter'.

 

You can track individual trips from start to stop simply by looking at the display after you turn the car off. It displays info from the time the car was started until it was turned off. However, it is only good for that specific trip and taking the same tip another time may give different results. I've never paid any attention to the instant mileage display. I do watch the Trip A mileage though to see if it's going up and down between fill-ups. I use Trip B to get data for an entire trip from the time we leave home until the time we return even if it's weeks later. The only semi-accurate data is to manually compute mileage based on actual miles driven and the amount of fuel pumped. However, that doesn't help one make adjustments while they're their driving. It'll show you real quick how much mileage is affected by fast acceleration, how much the battery is affected by over use of EV mode, etc. Lately, my goal has been to return home for any errand with the same or higher mileage on the CONS display, especially if my wife takes the car somewhere.

 

Welcome, well, yer 12v is a possible culprit, if weak, it's using energy.
yes, cold is different, everything takes longer to run optimally, air up, check that the emergency brake isn't dragging, clean the in cab air filter, check the ice (internal combustion engine) oil level and air filter.
Get studs, front wheel drive with undef-eatable traction control requires studs...in NH

 

It has been a rainy week up around Southern NH, I believe. Rain kills MPG for all cars.

 

- Winter temps greatly influence the mpg, due to how the battery performs when it's colder. I live in WI, and my mpg dips down from around 54 mpg in summer to around 36 mpg during the cold parts of winter.
- winter gas, I'm told, has a different mix, and seems to give worse mpg.
- more in-town driving will certainly affect things as well.
- tire pressure gets lower as the temperature dips, and lowers your mpg.
- the onboard mpg gauge is not accurate, unfortunately. Mine reads higher than actual mpg by 5-9%. Do consistent fill-ups and keep track of them.
- if your 12v battery is dying, the cars spends energy trying to charge it.
- there are also things that affect driving (wind, grade, road condition, passengers, weight, and mysterious unknowns).

Here's my mpg, with seasons:

 

I believe that function is in the 2013 and later models. I remember it from borrowing a 2013 dealer loaner one time. My 2011 doesn't show that. Wish it did. Well, in a couple of years I'll purchase a used 2014, keeping on my schedule, and then I'll have it.

 

Good point, I didn't know that wasn't on all Gen 3's.

 

True, but the magnitude of that effect often tends to be greatly exaggerated. That battery would be fried in short order if it were absorbing enough energy to noticeably affect fuel consumption.