Only 38 mpg right now

could be the 12v, hybrid battery, worn engine, tyres, many different possibilities

 

Do the following:
1. Clean your maf sensor
2. Do a bottle of redline fuel treatment
3. Do the reset on this video
4. Enjoy your mpgs again.

 

That's what I'm getting on my 2011 Prius as well.

 

Without history of maintaince provided, it can just low tire pressure.

 

I think its just a weak hybrid battery. I have 165k miles, quite a lot lower than his 230k but I'm guessing he has a lot more highway miles. I check my tire pressure every month, and brakes/etc are all fine. I get the same mpg, 38-39 consistently. My average speed is 23mph in my city commute. I've often thought of just replacing the battery but I think I'll just wait until it dies.

 

What brand/type of tires are you using? That does make a difference

 

I have over 200k. I think you are right about low mileage caused by a weak hybrid battery. I still have the original and dealing with lower mpg. Getting only 37-40 mpg.

 

I'm 66 YO...and don't get the MPG I did at 16 YO either. Just saying.

 

I have both a 2008 and 2011 prius, both on original batteries. My 2008 with over 250,000 miles gets about 47 MPG, and my 2011 (which I just got used) with 150,000 miles gets 38 MPG. Will definitely try the basics of cleaning MAF sensor, checking air filters, and monitoring batteries in Dr Prius, but I'm hoping we can boost MPG without new batteries.
I do know it has been rarely driven this past year, only about 3 fill-ups in the past 9 months, so I'm thinking we may just disconnect the 12v for a minute to reset and recalibrate. Has anyone seen that help?

 

load test the 12v, and clean the egr circuit