Tacoma low gas mileage questions

I used to get over 300 miles to a tank. 18 mpg every time. Now, with 230,000 miles I think I need to replace something that has worn out.
One clue that may be helpful is from a full tank to a 3/4 tank I get 100 miles, then to half a tank I get 50, by the time the gas light comes on, I'm lucky to get 250 miles a tank. It's an average 14-15 mpg.

Could it be a bad oxygen sensor? My mechanic said my truck has 4. Maybe I need to get my fuel injectors completely replaced because I've tried several fuel cleaners and none of them make a difference like they used to.

I also bought the cheapest tires I could get from a hackbit tire store where the guy couldn't even read my odometer!! I had to show him how. Would cheap tires really reduce gas mileage to 15mpg? Please let me know if your tacos had problems when they got to this amount of mileage. And what problems have you seen that affect mileage this drastically?

 

Soft rubber compound will increase rolling resistance and reduce mpgs. Try adding some air and see if higher psi brings you back up.

There are many factors that could reduce mpgs. You might need new spark plugs, clean MAF sensor, air filter could be dirty, winter fuel...so many more too.

 

Air filter clean? Psi correct in tire's? Bad gas?

 

I had a mechanic tell me a dirty mass air flow sensor (MAF sensor) can lower gas mileage. It's easy to remove and clean. Just make sure you get MAF cleaner from your local auto parts store.

 

Switching the rear diff oil to synthetic made a big difference in my truck

 

First thought:
Have you changed plugs? Coils? Primary and secondary air filters?

Other thoughts...

Tires tech is BIG. Most mid-level & up brand names are going to LRR (Low Rolling Resistance) compounds these days. What kind of tire are you running? Road? AT? MT?
Where do you drive? Temps? Terrain? What PSI do you run?

How do you drive? Time lights? Jack-rabbit off the line?

How much gear are you carrying?

Final thoughts...
O2 sensors, fuel filters, cats? regular or synthetic oil? How often do you change oil?

 

It shouldn't have

 

I don't know... it seems to roll a lot better off the throttle (I did change the tranny oil, as well) Op, start with the spark plugs