Coming to Grips with Hydrogen Fuel Economy - 2016 Toyota Mirai Long-Term Road Test

2016 Toyota Mirai Long-Term Road Test

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2016 Toyota Mirai: Coming to Grips with Hydrogen Fuel Economy

by Dan Edmunds, Director of Vehicle Testing on August 18, 2016

2016 Toyota Mirai

Our 2016 Toyota Mirai is a unique machine powered by an unfamiliar fuel — hydrogen. How far can it go? What is the consumption like? These are among the many questions we wanted to answer.

Let's get started.

The Mirai is easy enough to fuel up. It takes about as long as a gasoline fill-up — five minutes — and the equipment isn't hard to use. And although hydrogen cars are still in their infancy, finding a station hasn't been too much of a problem. There are two near the office, one about halfway along my commute home, one near the John Wayne Orange County airport I frequent and another out near where we test cars. I have a decent array of choices, in other words, and I've never encountered a wait at any of them.

So refueling hasn't been a huge issue, Jay's saga notwithstanding. The concerns boil down to the usual ones: fuel consumption and range. (I'll tackle cost in a future post.)

The Mirai's EPA consumption rating is 67 mpg-e, where the "e" stands for gasoline gallon equivalent. But what is the hydrogen equivalent? How is it sold? It turns out that 1 gallon of gasoline is equivalent to 1 kilogram of hydrogen, and hydrogen fuel pumps display the amount dispensed in kilograms.

What this means is that the Mirai's 67 mpg-e rating translates to 67 mpkg. And since the pumps sell it in kilograms, the math required to figure fuel economy is utterly familiar. Simply pretend you are buying gallons and proceed as normal. Handy.

2016 Toyota Mirai

Through the end of July we've amassed over 5,000 miles and refueled our Mirai 24 times using six different stations — the five I rattled off plus another one closer to downtown LA.

The Mirai's tanks (there are two) hold just under 5 kilograms of hydrogen at a pressure of 70 MegaPascals, which is 10,000 psi. Hydrogen pumps serve up two choices: H70 (70 MPa or 10,000 psi) or H35 (35 MPa or 5,000 psi). Since a gas always completely fills the tank it is housed in, in gasoline liquid terms you can think of an H70 fill as a full tank and an H35 fill as a half tank.

There's no reason to use the H35 pump when filling a Mirai, in other words. Not unless the H70 one is broken.

With a tank filled with the H70 pump, the Mirai's range is rated at 312 miles. We've not yet run it down to empty, but we have come fairly close. Our best range was 245.2 miles, and we've driven more than 230 miles a couple of other times. The distance we've covered has thus far been dependent on when we've been in the neighborhood of a pump.

2016 Toyota Mirai

I'll give you the numbers earlier than usual, because there's a lot to talk about.

Worst Fill MPKG: 41.9
Best Fill MPKG: 74.3
Average Lifetime MPKG: 56.7 (1.8 kilograms per 100 miles)
EPA MPKG Rating: 67 Combined (67 City/67 Highway)
EPA Range Rating: 312 miles
Best Range: 245.2 miles
Current Odometer: 5,190 miles

Our best tank of 74.3 mpkg beat the rating by 11 percent, which illustrates the elevated potential of a relaxed driving style. On the other end of the spectrum, our worst tank of 41.9 mpkg occurred at the track as we were busting out several wide-open acceleration runs. By all rights it should have been worse. The Diamond Bar hydrogen station we used is about 10 miles from the track, which means this mpkg figure was buoyed by 20 sedate freeway miles that the gasoline-powered cars that visit the track don't get (we refill them immediately before and after testing).

Overall, our Mirai's average observed fuel consumption of 56.7 mpkg lags 15 percent behind its rating. We're using 1.8 kilograms of fuel every 100 miles instead of 1.5 kilograms per 100 miles, in other words. That's partly because our all-new Mirai has attracted a lot of attention from Edmunds execs, and most of them live in very congested areas. Yes, the Mirai's city, highway and combined ratings are equal, but navigating West LA traffic can be a cutthroat business.

At this point it's looking like hard driving may punish the Mirai's fuel consumption as much as an easygoing and relaxed approach can reward it. But we need to investigate further. A pump located near Harris Ranch makes it possible to get to San Francisco, Sacramento or even Lake Tahoe and back. Look for someone to make one of those runs in the near future.

Dan Edmunds, Director of Vehicle Testing @ 5,190 miles

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