Sudden drop 6-7 mpg’s??

[Meatball]

13’ RS 1.4 auto...I drive the same 10-12mi trip daily. Putting along normally with no hard accelerating or aggressive driving. I use cruise control on most of it at 53-55mph and my trips always average about 34 mpg...always! I fill up at the same gas station using the same fuel and octane every time. Nothing has changed.

Two weeks ago I noticed my trip netted me only 32 mpg. One week ago the highest I could muster was 30....now it will only give me 27!! Whats going on here?!?

Theres no codes pending. Car sounds/runs fine like always. Has just 50k mi. I keep my vehicle very well maintained in every aspect. Anyone have ideas?

 

[5.0]

Bad gas, tire PSI, dirty air filter, cold weather, driving against a headwind, running the A/C will all affect MPG. Could be anything.

 

[shibbs]

Your station must have switched to winter blended fuel.

 

[Meatball]

Now in the 22mpg range...gas is fresh, air filter is new oem 2 months ago, tire PSI is proper, a/c not used and no gale force winds to speak of. Winter fuel would cause a 2-4 mgg drop but not 12-13. Car still runs perfectly fine with zero indication anything is awry except for mpg readings. No real explaination for the nose dive in the past month. Dealership says if anything was wrong, it would throw a code. They wont even dig into it (warranty) without a code. Any exploratory time they’d have into it would be on MY dime if I choose.

Seems like techs nowadays assume a car is tip top shape unless it trips a sensor somewhere. I guess Im stuck with terrible mpg’s until it throws a code or leaves me stranded. Then warranty will cover it. By then, whatever issue it has will have compounded and the repair cost will be substantially more than if dealt with early on. Backwards thinking in my opinion.

 

[dannyg]

Weird. Spark plugs? Injectors? Try a can of Seafoam or other gas treatment? Try a couple of tanks of Premium? Not at all sure. I see a few MPG variation hot/cold, fast/slow, etc., but not 12MPG...

 

[SuperFudd]

If it were winter blend it would not change gradually and not 12 mpg. Perhaps try another brand of gas.

 

[Tesseract_Indeed]

I've had the same thing happen with my 2012 LT 1.4t. No codes, no explaination. Just over the last month or so I went from 30mpg steady for several months down to 20mpg. Mine was a little lower than yours to start because I drive a lot and like to put my foot into it, but I don't run the piss out of mine down to 20mpg. No idea. I guess i'll try a new station for gas...?

 

[NDarkling]

My money is on winter blend.

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[OssiansFolly]

My car went up when I changed out my purge valves, air intake, and did an oil change. Unsure how, but I am assuming this isn't going to be a perfect science with the right answer.

 

[Italianjoe1]

I think it's the PCV system starting to fail, mine is showing worse and worse MPG over time with no other issues. Drove the car on a 700 mile roadtrip, averaged 32mpg, should be higher. Around town it's low 20s. It is full time A/C use and tuned, she drives like a maniac, but it used to be higher.

 

[OssiansFolly]

When I hear roadtrip I also think the vehicle is loaded with stuff and people. Could also be a weight issue along with the terrain you're driving in. If I drive through the mountains with a car full of people and luggage...then I expect a drop in mpg.

 

[JTee2017]

Lurker. . . OP hasn't even been back to respond to any replies. . . Lurker and leaves open ended posts in a lot of threads.

 

[Italianjoe1]

When I hear roadtrip I also think the vehicle is loaded with stuff and people. Could also be a weight issue along with the terrain you're driving in. If I drive through the mountains with a car full of people and luggage...then I expect a drop in mpg.

Yes there was more load in the car than normal but it was only me and a small bag, it normally has the wife and baby in the car when she's driving so an extra 300lbs doesn't explain a drastic difference, 1-2mpg sure, but not much more. The terrain, well, it's Florida, it's all dead flat lol. Drove from Miami to Jacksonville and back.