MPG weirdness

isn't that due to engine warm up?

 

You probably are looking at an MPG number that is not a long term average........but resets every time the engine is restarted.
For the first 10 minutes or so, that number can be REALLY low.

 

OK here's what I did to my mileage back up. My car sees short trips in the 3-5 range every day and like you my mileage dropped down to what you're seeing. Take a long drive once and while to clean everything out. After spending a couple weekends doing some highway driving I can now easily get 52-53 mpgs with the A/C on highway driving at 65 mph. BTW I just turned 100K miles on my 2010 III. I purposely will take a run down to Cabela's in Wheeling once a month just for the heck of it to get some highway miles on the car.

Go to the auto parts store get a bottle of Techron and fill your tank with Top Tier gas like Shell. Now the easy part go out for a long drive say this weekend or next. A long drive is for several hours so everything gets nice and hot and the engine runs the whole time on the highway. Not for an hour but for several hours, leave home at say 8:00 to maybe 5:00 or 6:00 stopping somewhere along your trip for lunch. Just set your cruise control on 65 mph and enjoy the ride. Take a trip up to the AACA Museum in Hershey or take in a car show at Carlisle maybe Columbus or Niagara Falls for the day. Try this first before tearing the car apart cleaning different systems as others will suggest.

All vehicles need a long run once and a while but for some reason many don't realize it.

Don't go by the factory display for mileage numbers it will read a little high. Short trips with the warm up cycle will kill your fuel mileage. You can only look at numbers where you've had the car out for an hour or more with few start up cycles. Plus Pittsburgh with it's hills will always knock your fuel mileage down five or more MPGs over people who live in relatively flat areas.

 

AND many don't seem to realize that extremely short trips when the engine is COLD will just naturally produce low MPG numbers.....and that is perfectly normal. And there is nothing you can do to "fix" it.

 

Yep

 

subway is not healthy, your Prius was literally affected by it.

 

The only way your are gonna get accurate mpg is over a full tank, or multiple full tanks.

Hand calculated with the gallons put in and the miles achieved.

The dash is not accurate.

 

That sounds normal for warming up a cold engine. Engine block warmup takes a significant amount of fuel. This cost must be paid with every cold start.

Nope, his Gen3 Liftback doesn't have such an automatic feature. If it did, or if he had manually reset it, it would have read much lower than he reported at the 100 yard mark.

When I reset mine at a cold start, then it can read down in the single digits for the first few blocks. By ten minutes, it has climbed most of the way back to normal.

In the short term, especially around cold starts and hills, mpg is highly variable. While the dash display has a built in optimistic bias, it is accurate enough to help reveal and characterize this great variability.

Then use the refueling hand calculations for the long term accuracy.