MPG reading error?

Asked by Apr 08, 2017 at 01:00 PM about the 2016 Toyota Prius

Question type: General

I bought the Toyota Prius 3 in November and mostly love it. The GPS really
sucks though. My question is about the MPG readings. I reset the trip A
meter every time I fill up and last time it says that for the 753.7 miles I
traveled on that tank, I got 77.4 MPG. When I filled up at that point it only
took 10.45 gallons of gas. By calculation that comes to just over 72 MPG.
By rough estimate, I noticed that it was about 5 mpg less than it says every
time I filled up.So is the meter wrong? Or am I being cheated at the pump?  

2 Answers

92,355

I would believe the GPS over the regular odometer. There is no guarantee that the fuel meter in your car is absolutely accurate either.

35

Great job with your hyper-miling. The Prius trip meter, odometer, speedometer, and fuel efficiency calculations use wheel rotations not GPS readings. Your Prius believes it used 753.7/77.4 = 9.74 gallons of gas. Using different cars and different gas stations, I've found that cars often systematically over or underestimate fuel consumption more often than gas stations do. A gas station could make illegal profits by mis-measuring, but their measurements are tested by the state department of weights and measures in most states. Cars don't measure the fuel flow so precisely. Usually they don't measure it directly at all, only infer it from air intake flow or manifold absolute pressure and oxygen levels in the exhaust. If this discrepancy is unusual for your Prius and gas station, the pump probably filled the tank with about 0.7 gallons more than the last time you filled up. Hopefully the tank didn't quite fill the previous time rather than overfilling at this gas station. Please don't top up or let others top up after the pump stops filling. Doing so risks filling your charcoal canister with gas, fouling it, leading to evaporative emission pollution and costly repairs.

1 of 1 people found this helpful.

Your Answer

Toyota Prius Experts

  • #1
    TupeloMS
    Reputation
    680
  • #2
    raae
    Reputation
    640
  • #3
    Tom Demyan
    Reputation
    450
View All

Related Models For Sale

Used Toyota Camry
79 Great Deals out of 2,182 listings starting at $1,900
Used Toyota Prius v
41 listings starting at $12,800
Used Toyota Corolla
201 Great Deals out of 3,594 listings starting at $2,411
Used Honda Civic
286 Great Deals out of 4,290 listings starting at $1,815
Used Toyota Prius c
122 listings starting at $8,495
Used Honda Accord
63 Great Deals out of 1,175 listings starting at $1,488
Used Toyota Prius Prime
20 listings starting at $29,995
Used Toyota RAV4
54 Great Deals out of 3,259 listings starting at $1,000
Used Honda CR-V
52 Great Deals out of 2,552 listings starting at $2,895
Used Toyota Prius Plug-In
4 listings starting at $18,450
Used Chevrolet Volt
366 listings starting at $2,295
Used Honda Fit
18 Great Deals out of 662 listings starting at $2,500
Used Toyota Yaris
34 Great Deals out of 725 listings starting at $1,991
Used Nissan Altima
86 Great Deals out of 1,253 listings starting at $2,200
Used Ford Fusion
137 Great Deals out of 1,729 listings starting at $1,995

Used Cars For Sale

2017 Toyota Prius For Sale
33 listings starting at $24,995
2016 Toyota Prius For Sale
5 listings starting at $21,888
2015 Toyota Prius For Sale
8 listings starting at $16,396
2014 Toyota Prius For Sale
12 listings starting at $13,900
2013 Toyota Prius For Sale
9 listings starting at $13,486

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.