recent drop in mileage for 2006 Gen 2 Prius

- Have you read This Thead Yet?
yes

- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
I'm basing my conclusion on how rapidly I've needed to fill her up again. Now three times per week. Used to be once per week.

- What fuel economy are you expecting and why?
One or two fill-ups per week, as I used to experience.

- What are the approximate outside air temps?
Typical PNW temps for this time of year. Hovering near 40F.

- How long are your trips?
My commute is 21 miles each way.

- 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?
Stop and go driving? Yes. Nearly all city. Avoid highways around here like the plague. Average speed 30MPH.

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

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

- 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)
Not sure. The smaller one? About 6 years old. Had it replaced when it died at that point.

Have you had your alignment checked? Any pulling or abnormal tire wear?
Aligned done regularly. No abnormal wear.

- 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).
Buy tires at Costco. The ones that are always on sale.

- What are your tire pressures?
Normal.

- 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.)
Previous car? In 2006? We drove a 1992 Toyota van (the egg-shaped one). Had a different commute then. Apples to oranges.

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
No option to stay in electric only. Brake normally, although hard when traffic snarls unexpectedly.

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
No

- 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?
Auto set to 70F

- If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
No. I was told it's just getting old.

 

I will figure out what the tires and PSIs are. It's not information at the top of my head. And I had no idea, out of all of the information in that long list, that it was the most critical. I am not a car person. I love my Prius, and want to keep using it for as long as possible. That's why I'm here.

As for calculating mileage per gallon at the pump...Is that as simple as I think it is? Record mileage at each fillup, record gallons added, and divide the difference in miles by the number of gallons?

 

> yes

 

(I have not forgotten about the tire pressure, but I have been able to start calculating mileage after three visits to the gas station in the past three weeks.)

The calculated mileage numbers are a little variable so far (36.2694 MPG and 42.2078 MPG). I'm wondering how many readings would comprise a decent average...

 

Getting warmer? Somewhat. It is spring in the Pacific Northwest, and we're finally getting north of 10C.

 

Actually, currently Seattle suburbanite, former Vancouver suburbanite, former Tokyo resident, former rural Massachusetts student, and former New York City suburbanite. Celsius makes sense.

 

After meticulously tracking my mileage for months, I found that the average at 12 years and up to and beyond 200K miles was hovering at the 40 MPG mark. But then my poor Prius died. I suppose that's a topic for a separate thread, but suffice it to say that the dealer I had it towed to said that both the inverter and transmission (transaxle system, probably) were dead. He quoted USD 14K for repairs, at which point I had her towed to my more trustworthy mechanic for a second opinion (which I am still waiting on). In the meantime, we managed to buy a used vehicle. Another hybrid. This time a Lexus (CT 200h). Based on Prius technology, I hear, but definitely a different animal.