I've been getting 38.5 mpg lately. I did a Dr prius check..battery has 64 percent life. Got a catalyst bank 1 when running a smog check. Could it also need replacing catalytic converter?
Also check your ECT- (engine coolant temperature), MAF- sensor, air filter; that'll also cause you to run rich. How many miles on her and what maintenance has been done to her?
Voltage readings like that is 99% of the time a failing cat. When O2 sensors fail, they'll often lag or just have weird out of range readouts on the ECU. I'd start saving for a new cat or look into cleaning. If you do buy a cat, do not buy cheap; get OEM or equivalent. If you want to clean, I'd replicate the formula best as possible for CATACLEAN using the MSDS, but up the dosage (don't get too crazy). Other folks also use acetone and other solvents, but that's your call.
