Mileage dropping and dropping and....

- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)

In the last 2 years, I've gone from a solid 47MPG to now an avg of 41.7MPG. I have an excel sheet from day 1 (mile 0) of ownership. Lately, I've been getting 38-40 (last month or so).

- What fuel economy are you expecting and why?
I'd expect around 44-45 based on travel time, etc.

- What are the approximate outside air temps?
Varies from 50s up to 80s

- How long are your trips?
15-30 mins

- 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?
90% highway. Smooth, not that much stop and go.

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

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

- 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)
Just changed the battery less than a month ago (2 tanks ago). Mileage is unaffected

Have you had your alignment checked? Any pulling or abnormal tire wear?
Yes; No

- 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).
Yes.

- What are your tire pressures?
42/40

- 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.)
What? Irrelevant, lol. It was a Camraro, but that was nearly 6 years ago.

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

Without thought; easy and gently.

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
Heavens, no. From day 1 - on, and drive.

- Are you driving using D or B mode?
No. I'm using D as in 'boy'. Kidding. Only D.

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
Very rarely. When the AC is on 78. Heat 76. But it's usually off. I do understand the impact of milage, but again, it's very rare that the AC/heater is on.


- 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?

I bought new tires at the beginning of the year, and I hit another drop. I figured this would go up slowly, but it hasn't yet. Tires aside, my mileage has been steadily decreasing over the last 2 years. We moved, but we moved back to the same area and commute than I was achieving 44-45 MPGs.

I'm stumped. Please interrogate me.

 

Thanks.

Commute 1 - 15 minutes, mostly flat - about 5 miles
Commute 2 - 34-50 minutes, 90% freeway. Going from high to low elevation - about 18 miles
Commute 3 - 15 minutes, mostly flat - about 8 miles. I avg about 60 MPH in the am, with a peak of about 75MPH. But based on prior tanks, and knowledge of my car, etc - I used to get over 40 at the *minimum*. Today's tank yielded 37MPG.

I've changed tires twice. I went back to the OEM tires in January this year. I'm right at 72k.

 

Alright! Thinkers.

1. 72k
2. No
3. No
4. No
5. No - How do I?

 

Tire - Goodyear Integrity. Went back to OEM. Yes, they are on all 4 wheels.

Haven't checked the rolling of the wheels. I live in SoCal, and it's great weather 95% of the time. IE - no rain.

Yes, we have 2. They aren't allowed in the Prius. Not once, lol. We have a Jeep that they utilize.