Consistently getting 35-37 mpg, nothing higher

I have a 2004 prius with 149k on it and can't seem to break into the 40 mpg range. I live in an area with some hills, but nothing too crazy. I have even had trips of 60+ miles on pretty flat freeways/highways/roads and have only hit 38mpg driving with a very light foot, coasting down hills, coasting to stoplights and using cruise control. I have tried keeping my speeds low and just cant get great gas mileage. I am not sure what else to try.

In the past few weeks I have had the oil, transaxle and inverter coolant changed and the waterpump was changed 15k ago. I also had the spark plugs changed, air filter and have new tires.

Does anyone have any clue as to what could be wrong or what I am doing wrong? Could it be my batteries?


btw, I bought the car used a few months back and have been getting the same mileage since I got it. I have not noticed any improvement from any of the maintenance I have done.


Here is the Survey
- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
35-37 I am doing it via math and via the trip computer

- What fuel economy are you expecting and why?
40+

- What are the approximate outside air temps?

70s

- How long are your trips?
Mostly 15-20 mins with many 30 min to 1 hr

- How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving?

70/30 between city and freeway. City=30-55 mph Freeway=65-75 cruise control. Stop and go in city and free flowing on freeway

- What region/state are you in? (if you haven't set your location in your profile)

Los Angeles, California,

- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)

Gentle hills, flat with a few steep hills

- Is your oil overfilled? (i.e. above the full mark on the dipstick)

No

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)

One year

Have you had your alignment checked? Any pulling or abnormal tire wear?

Yes, had an alignment done recently

- Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15).

Stock rims, Doral SDL 65

- What are your tire pressures?

38 all round

- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
2001 Lexus IS300. I got 17mpg with HARD driving

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?

I am trying to drive it for best fuel economy. Not racing, coasting most of the time. Normal brakes

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?

Yes

- Are you driving using D or B mode?

D

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?

Very little AC, sometimes heater

 

yeah, my warm ups are not long at all. I would say under a minute so I do not think that is the culprit.


I did not buy the tires. they came with the car. I was a little put off by that, but hey, the other guy paid for them so I cannot complain too much.

Yeah i know that they are not LRR, but I figured even if it gave me 5mpg like you are saying, I am still not where I should be in terms of MPG

 

just did. I was getting perfect voltage

 

i followed this guide. And i have not driven the car today.

- Without brake pedal, press the Power button once and release to enter ACC mode
- Press and hold the MFD Info button, then turn the headlights on and off three times to enter Maintenance mode; release Info button
- Press “Menu” (on screen)
- Press “Display Check”
- Press “Vehicle Signal Check” - the battery voltage is shown and should be about 12.4 to 12.8 Volts (normal for an unloaded battery)
- Again without brake pedal, press Power button and release to put a current load on the battery - the voltage should stay above 12.0V (if less than 12.0V the battery is not well, or there is a fault or unusual load somewhere)
- Press brake pedal and press Power button once to enter "Ready" mode - the battery is now charging at about 14V (if less than 13.6V or more than 14.4 there may be a problem with the charging circuit)
- Turn car OFF to leave Maintenance mode

 

to get into acc voltage was 12.4, then when i pushed the power button again I got 12.1 then in ready it was 14.4 or 14.5

 

hmm. i will do some research on the cleaners and see what i come up with.

 

oil seems good as it was just changed and is at the correct level. i put a bottle of the cleaner into this tank so we shall see what happens as it goes through the system

 

ill check the level in a few. if it is too high, what is the best way to get it to the correct level? drain and hope for the best?

 

so my oil was below the full mark so that is fine. could it be my 12v even though it has the right voltage? could it just be the age? Or is there something wrong with my HV battery? I notice that sometimes at stoplights or something if I have green (all balls full) on my MFD the engine will start revving all by itself. I read that it could be just trying to get rid of excess charge, but is that right?

 

i have not figured this out yet..