Unusual Gas Mileage

1) the tank has a bladder which does not allow even filling every time.

2) you don't need a tune up.
if anything, you should recondition the battery.
the only thing that prius don't like is not being driven.
batteries degrade from sitting.
the battery would affect city driving much more than highway due to the stop and go nature and regeneration vs cruising on mostly engine.
a weaker battery will not be able to absorb as much energy regenerated, nor produce as much as a newer one.

 

Your results look "normal" to me.
Steady state driving will almost always yield a higher average MPG number than stop-and-go situations.......up to a point.

This is partly because the stop and go usually involves shorter trips.
Longer trips averages out the startup penalty more.

 

i haven't. most here buy the prolong reconditioner for less than a private company charges, and do it themselves.
use caution, there are a lot of scammers out there.

 

There is a difference between "city" driving, that is driving at a steady but slow speed, and "stop an go" driving.
With most vehicles, you get the best mileage at a STEADY speed of 40-50 MPH.
It goes down from there with a lot of stops or much higher speed.

Maybe you do NOT need to be messing with your battery.
"reconditioning" is mostly a myth. The gain is small and short lived unless maybe you start early and do it fairly often.
Taking one shot at it is a total waste of time and money.

P.S. Bisco has NINETY THREE THOUSAND posts on here. Have you read many of them ?

 

prolong-battery-charger

 

ignore the priuschatter on priuschatter hate above, and do your own due diligence

you can test the battery health with dr. prius app

 

I get lower mpg in the city than on the highway. Upper 30's vs mid 40's for city vs highway seems about right for my Gen2. There's probably dozens of reasons why this is contrary to the EPA. If there is stop and go traffic on the highway during my commute, I get better fuel economy. I can only guess that the EPA city tests mimic my stop and go highway traffic driving style but not necessarily my city driving.

Anyway, I would be worried if I averaged 37 mpg in my Prius. Since you got 47 on the next tank, you're matching what I get for mostly highway driving. 10 mpg is a huge difference but with one data point, it could just be a fluke.

 

The EPA (and CAFE) City test cycle is most definitely "stop and go", not steady speed. Here is the official speed vs time profile:

With a Prius, you get the best possible MPG at a steady speed of 15 to 20 mph, and can exceed 100 MPG this way. While this is very impractical in common U.S. use, some Japanese commuters were able to push this to get some incredible three-digit MPGs and four-digit single-tank distances.

Don't put much stock on that EPA twist of having a higher city than highway score. It is mostly just an artifact of the artificial fudge factors contained in the EPA scoring system, used to discount the high MPGs achieved by expert drivers running special speed profiles on stationary dynamometers, down to the more typical numbers experienced by ordinary drivers in real world conditions. The EPA's equations have quite different city and highway fudge factors.

Almost nobody has an actual driving profile that matches the official EPA - CAFE cycles. Some Prius drivers do get better in city driving, while many others do better in highway conditions. Because the EPA scoring system contains artificial elements, and most likely doesn't match your driving patterns, don't worry about which of those groups you are in. Don't overthink it.

 

were both tanks filled at the same station? Were they either one off brand gasoline? Could it have been an e-85 crap refill either by your mistake or because the tanker misfiled it? Much of the summer gasoline is crap especially in places like California. The oxygenates that refiners put in antismog blends to meet emission standards to help combustion, minimize NOx pollution are very poor energy to volume fuels. I’d try more tests with different brands before more involved analysis. That being said it takes a bit of relearning to drive a hybrid for max mpg especially in city driving.

 

THAT is not a good thing to do.
It can plug up the evap emission loop and cause the engine to run bad.
MY owners manual specifically says to NOT do that.

 

Same station a few days apart can be a bad batch of gasoline or a misfiled tank. I’d try more tests over the next few weeks with different brands before more involved analysis.