I'm steadily losing mpg on highway. very hour or so it keeps going down further. Moving across coun

For anyone else scratching their head, P0101 is for Mass Air Flow sensor.

What cleaner did you use, one spec'd for MAF?
Did check engine light go on, alerting you, and after the cleaning has it gone off?

How much weight in the car?
What's the temp where you're driving?
What speed are you doing?
Headwind, tailwind?
Grade changes?

 

Yes, typically mpg should rise on long drives like this as it eliminates the cold-start penalty to only the first startup of the day.

Besides the vehicle itself, there are WAY too many variables to nail this down and one is direction of travel. Heading into colder weather is a big cause. Heading west from Chi-town? You'll be climbing for a long time.

 

That statement is grossly misleading.
Carrying a heavy load and going faster than "normal" will NOT result in better gas mileage.

Not enough data to say what he is seeing is not normal.

AND how the indicted mileage reacts depends a lot on when it was last reset.
If that average is over many days and many miles, the fluctuations will be less noticeable.

 

Headwinds increase fuel consumption, and so do low temperatures.

 

Head winds.
Drastic temp drop.
Speed increased.

You are NOT resetting the fuel mileage monitor, are you ?

 

Yeah this minute-by-minute mpg status may be problematic, similar to watching your investment portfolio too closely.

 

I didn't say it was or would be "better". I said it should rise from the first tank of the day. Every reading could still be below EPA, for example. I also didn't speak in absolutes.

 

One more try and then I quit.

First, you don't KNOW that the conditions are identical.

Second, when you replaced the battery the MPG calculation probably got reset and now will be more sensitive to variations than it was before.

Third, something else might have changed.......like a brake dragging.
There may have been a seasonal change if the fuel formula.

Lastly, your car is getting older. That very likely will happen with EVERY car if you drive it long enough.
Some sooner, some later.

Obsessing over things like this is not good for your health.

 

I’m experiencing on our 2015 Prius. 37 -38 mpg mixed city and Highway driving. Manual figuring to get the mpg. We have the original battery and MAF sensor has never been cleaned. We have just over 41,000 miles on it.

 

no need to clean the maf at 41k, has the mileage dropped?