So I get my RC F Sport maintenance regularly. I use to get a mile range of 310-330 now when I fill up I get 262-274 on full. I recently did a fuel cleaner, I went to put my car on a reader nothing is showing up. I need help guys.

 

Aceito - I personally wouldn't worry too much quite yet - Keep in mind that the "fuel range" is based on the last tank so it may vary a bit based on your driving. Make sure you do a reset when you fuel up next time (reset your trip information and such). Keep in mind that at this time of the year, with slight cooler temperatures and whatnot, you may experience some variation in your mileage range. I would wait a bit and then see if that improves before doing anything....

Also, check your tire pressure....I always put a bit more in the cooler/colder month

 

This^

But also, have your driving habits changed? More or less aggressive?

 

No I drive normal I believe.

 

Were the tires changed recently?
Is air pressure what it should be?

 

Whats your milage? I know for people with high milage changing the spark plugs and resetting the ECU helps immensely with power and range.

 

I have about 60,600 miles.

 

Have you had the big 60k service then? the 60k service includes changing plugs.

 

I get worse gas mileage in the winter, on average, compared with summer. I think this is mainly due to defrosting the car. So I could see my range calculation decreasing during that time.
Then I noticed it looks like your from AL, so that's likely not a shared experience :-)