Poor fuel economy, i have 2010 Prius with 135k on it up to

I suspect it needs repair, but it might only need maintenance.
Have you had it looked at at all?
Did you recently change spark plugs?
Change coolant?
(You should have)

Are the brakes dragging?

 

Browse through the questionnaire below for some ideas of things to check. But note that this is intended mostly for new Prius drivers who never got good MPG, not experienced drivers who suddenly have reduced MPG, so it isn't an ideal troubleshooting list for your situation. It includes the 12V battery problems, but doesn't cover brake drag, failing hybrid battery, or most engine problems.
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

 

the 2010 is prone to a lot of build up and clogging. you will need to run through the threads regarding intake manifold, pcv, throttle body and etc. check out nuts about bolts you tube site.
this is assuming you're up to speed on all standard maintenance as mentioned above.

 

At 135k if you haven't you are overdue for spark plugs (125k), engine coolant (100k), and a transmission oil change (100k). More than likely those wont effect mpg, but they could. Plugs do wear. Besides that I've never noticed a difference in gasoline. All of the above is really easy and can be done yourself. The trans doesn't use a filter and just use pink coolant.
Then check resting battery voltage. If the battery isn't around 12.6 after sitting overnight you might need a new battery. Easy to check with a simple volt meter in the rear of the car at that battery.

 

I noticed 1 thing with mine. Like me, if you only do short trips, the mpg will suffer. one day, I drove 500 miles in one day, I noticed for the following week, my mpg AVG was much much better even with my usual short trips. And I noticed my battery had more power and would push me along much much longer Almost like I burned the gunk, hehehehe. but after about 1 week, I went down again. . It was almost like it needed a good charge. Now I'm back down to 41 mpg.

Good luck

 

it might just be the florida heat over the past couple months.

 

Too bad, but it looks like Initial Poster is gone.

With his miles I was thinking either PCV or EGR issues, more likely the latter. Or recent rear brake job, resulting in brake drag. Or new tires.

A few answered questions would have zeroed in, more 'n likely.

 

I had often wondered if maybe there is an increased drag in the engine from an a/c compressor needing more refrigerant oil (like pag or whatever they use now).

 

The Gen3's A/C compressor is not mounted to the engine, but is driven separately by an electric motor. So when the A/C is off, any such drag should disappear.

It would also seem that compressor drag large enough to cause that much MPG loss, should also blow the fuse on the relevant circuit.