As of this writing, we’ve owned our Toyota Highlander for nearly ten months. During that time, I’ve been meticulously tracking our mileage. And today, I want to share with you some insights.
I’ve actually been tracking three key pieces of info for each tank of gas:
- Average mileage (mpg) as estimated by the on-board computer,
- Average speed (mph) as estimated by the on-board computer, and
- Average mileage (mpg) based on actual miles driven and gallons used.
Overall, I’ve been averaging just over 20 mpg in mixed city/highway driving. As a reminder, we have an XLE with FWD, so we’re within 1 mpg of the EPA’s estimate for mixed city/highway driving.
Computer vs. real-world mpg
Are you curious as to how the computer estimates compare to my real-world estimates? If so, then check the graph below.
In this case, each dot corresponds to data from a single tankful of gas. It’s not perfect, but there’s a rather strong correlation between the what I’m calling the “estimated” and “calculated” mileage values.
The black line reflects the linear “best fit” for these data. For the stat geeks out there, r^2 = 0.83 — that’s a pretty darn good fit if you ask me.
For the record, I’ve been very careful in how I’ve been calculating the mileage. This includes filling the tank to where I can just see the gas, rather than letting the pump click off when it thinks I’m full.
As you can see, the computer estimates do get a little wonky at the higher end of the range, with the estimates sort of flattening out. But, overall, the computer seems to be pretty darn accurate.
Mileage as a function of speed
Are you curious as to how your type of driving affects your mileage? If so, then check out the graph below.
This is a plot of the mpg (based on my own calculations) vs. the computer-generated estimates of average speed (mph). This isn’t so much a measure of variations in my driving style as it is an indicator of the city/highway mix.
In general terms, higher speeds on this graph correspond to tanks of gas that included a higher proportion of highway driving. And, as expected, more highway driving results in better mileage.
Again, the black line reflects the best fit for these data. For the stat geeks, r^2 = 0.58, so it’s another decent fit.
Note that none of these tanks correspond exclusively to highway driving. It’s therefore not particularly surprising that these mpg values fall well short of the EPA estimates for highway mileage.
That being said, our Highlander does perform close to EPA estimates when we have it out on the open road. Is the mileage mind-blowing? No, not really. But it’s pretty close to what they promise on the window sticker.