What happens when you test the real-world efficiency of hybrids and EVs?

How do you put EPA mileage numbers to the test? You could buy a wind tunnel and a lab and start doing a massive science experiment. Or you could find 20 auto writers, put them in 20 different cars, and tell them they're in a contest of efficiency where the winner gets bragging rights.

Every year, the Automobile Journalists Association of Canada does the latter. About 20 of the country's top journalists come to take part in EcoRun, an event where automakers are invited to bring their most efficient models to one place for three days of fighting to use less.

In the past, it was all gas and diesel, but as the market has changed, so has the EcoRun lineup. This year, every vehicle had some form of electrification, and about half were fully electric.

EcoRun 2023 had 10 legs. Each driver swapped to another car at the end of each leg. Consumption of fuel and electricity were recorded. Rotating 18 drivers through the 18 vehicles (each driver drove 10 cars) cancels out most of the influence of one driver who doesn't care about winning. But all these auto enthusiasts care about winning.

Driving every vehicle on the same days and the same route in the same conditions levels the playing field almost as well as a test cell. That's why I'm calling this the best way to show how some of the most efficient vehicles on the market compare to their official estimates. Here they are, ranked from worst-performing to best, in relation to their EPA combined estimates.

Oh, and all of the PHEVs started each day with no battery charge. It was the best way to make it fair and was also the most representative of the long road trips this event is meant to simulate.

Toyota Prius Prime: 48 mpg

When Toyota redesigned the Prius, it finally made the car stylish; there's no denying the new car turns heads. Toyota also decided to emphasize performance over outright efficiency and gave the Prius Prime 220 hp (164 kW) and a 2.0L gas engine.

The Prime has an impressive EPA fuel economy figure of 52 miles per gallon (4.5 L/100 km), the best of any vehicle on this test. But on the road, the car delivered 48.1 mpg (4.9 L/100 km), 7.5 percent below its window sticker. Prime's best single segment was 62 mpg (3.8L/100 km), and its worst was 33 mpg (7.1 L/100km).

Hyundai Tucson: 34.5 mpg

The Hyundai Tucson offers conventional, hybrid, and PHEV drivelines, giving buyers plenty of choice. We had what was probably the best one for road tripping, the Tucson Hybrid, with a 1.6L turbocharged engine and 59 hp (44 kW) electric motor. The combination makes for 226 hp (169 kW) and 258 lb-ft (350 Nm) of torque. Hyundai uses a conventional six-speed automatic (minus a torque converter) for its hybrid drive system, and that makes it feel much more like a gas-only vehicle than the usual somewhat mushy CVTs used in other hybrids.

Pairing a turbocharger with a hybrid motor is unconventional since it adds complexity and cost to the system. Here it might also take away from the vehicle's fuel efficiency. Against an EPA rating of 37 mpg (6.4 L/100 km), the Tucson hybrid returned 34.5 (6.8 L/100 km). At 6.7 percent under estimates, it was the second of just two vehicles that didn't beat the official rating. Tucson faired worst in the uphill climb sections where fuel economy dipped to 24 mpg (9.7 L/100 km), a figure more in line with the bigger SUVs. On flat ground, it dropped to around 47 mpg (5 L/100 km).

Toyota Mirai: 74.7 MPGe

Next on the list was the Toyota Mirai fuel cell electric vehicle. Toyota continues to push the hydrogen fuel cell vehicle, but despite the massive automaker backing it, the technology and infrastructure needed to bring hydrogen to the mass market still seems awfully far away.

If you forget about filling stations, it's hard to deny that the Mirai is an amazing vehicle. It's quiet and smooth—basically a zero-emissions Avalon that's much better-looking. It also promises gas-like fill-ups instead of longer EV charge sessions. And it's efficient, returning 74.7 MPGe (2.22 mi/kWh) against an official rating of 74 (2.2 mi/kWh). One percent better than the estimate and just 0.84 kilograms of hydrogen for every 100 km 62 miles) of driving.

Honda Accord Hybrid: 44.7 mpg

Honda has redesigned the Accord for 2023, and that included a more powerful hybrid drive system that now delivers 247 lb-ft (335 Nm) of torque. Honda's front-drive system is unique in that it doesn't use a transmission at all. Instead, one of the two motors powers the front wheels in nearly every situation. In those rare situations where it doesn't, the gas engine drives the wheels directly thanks to a clutch pack. This happens at highway speeds, where many vehicles would use a 1:1 transmission ratio anyway. Honda says that this unusual arrangement is more efficient. It's probably also cheaper since it leaves out one of the most expensive components in a vehicle.

The Accord Hybrid Touring has an EPA-estimated 44 miles per gallon, and on EcoRun, it returned 44.7 mpg (5.3 L/100 km), 1.7 percent better than expected. Accord was also extremely consistent, with most legs of the trip posting numbers right around 53 mpg (4.4 L/100 km). Its worst leg was a mountain climb where the Accord delivered 30 mpg (7.8 L/100 km).

Honda CR-V: 38.5 mpg

Look under the hood of the 2023 Honda CR-V and you'll find the same hybrid drive system as the Accord, but with some extra hardware to deliver all-wheel drive. The AWD system and CR-V's larger frontal area cut into fuel efficiency, but the two return similar figures compared with their official estimates.

The CR-V Hybrid has an EPA estimate of 37 mpg (6.4 L/100 km), and we saw 38.5 (6.1 L/100 km), 4 percent better than estimated. Interestingly, it was about 6 mpg behind the Accord on each leg.

Toyota Corolla Hybrid AWD: 50.7 mpg

The most impressive part of the Toyota Corolla's figure? It had higher fuel economy than the Prius Prime, despite the extra weight of all-wheel drive. Corolla's 1.8 L engine and the electric motors driving the front and rear wheels on this AWD model deliver just 138 hp (103 kW), well under Prime's figure, and that may be what led to it scoring 50.7 mpg (4.6 L/100 km) on the test. That's 5.7 percent better than the 48 mpg (4.9 L/100 km) official estimate.

Lexus RX 500h: 28.6 mpg

Lexus sent the RX 500h hybrid, a model it calls a performance hybrid. Instead of the 2.5 L four-cylinder normally found in the larger Toyota and Lexus hybrids, including the RX 350h, the RX 500h applies hybrid drive to the company's 2.4 L turbocharged four-cylinder. The result is 376 hp (280 kW) and some rapid acceleration for a Lexus.

Its fuel economy estimate is 27 mpg (8.7 L/100 km), which isn't exactly high up on this list of fuel sippers. On the road, the Lexus RX 500h delivered 28.6 mpg (8.2 L/100 km), beating its estimate by 6.1 percent. It returned the worst single-segment figure—20 mpg (11.9L/100 km)—which was matched by the Range Rover PHEV on the same leg.

Polestar 2: 108.5 MPGe

The first electric vehicle on this list is the Polestar 2. We drove a dual-motor long-range model that promises 100 MPGe (3 mi/kWh, 20.7 kWh/100 km) and an official EPA range of 260 miles. On the test, the dual-motor car returned the lowest efficiency of any of the EVs, but it's hard to call 108.2 MPGe (3.2 mi/kWh, 19.4 kWh/100 km) a disappointment. That number suggests the Polestar 2 would be able to manage closer to 280 miles on a charge, which is a significant difference.

Kia Niro PHEV: 54.4 mpg

Kia's Niro PHEV returned the best economy of all of the combustion-engine vehicles on the EcoRun test. The boxy crossover shape doesn't look like it would cut through the air, but the lack of interior noise suggests it's quite smooth. It also shows that the polarizing rear side blades do their job of channeling air around the rear of the vehicle.

Niro's 1.6 L four-cylinder and electric motor return 180 hp (134 kW) and 195 lb-ft (265 Nm) of torque. With that powertrain, it returned 54.5 mpg, 11.1 percent better than the 49 mpg (4.8 L/100 km) rating. The Niro turned in better than 52 mpg (4.5 L/100 km) on every leg, with a best of 71 mpg (3.3 L/100 km), the best of the entire event. Niro PHEV's estimated electric range is 33 miles.

Oh, and the Niro PHEV was on snow tires for some reason, making the figure even more impressive.

Hybrid fuel economy tricks

Driving hybrids from Honda, Kia, Hyundai, and Toyota in succession showed that Toyota's vehicles operate very differently from the rest. In a Toyota, I've always found it easy to cruise along at around 60–80 mpg (3–4 L/100 km) in steady-state driving with it more difficult to engage EV-only mode.

In the Honda, Kia, and Hyundai, the instantaneous fuel economy was either at zero or 25 mpg (10 L/100 km). There was little to no middle ground. It was much easier to drive these vehicles in electric-only mode, even at highway speeds, and easy to do it for a longer time. Though they go about it in different ways, they seemed to achieve a similar result but required different driving styles. Toyota's was less work.

Lexus RZ 450e: 120.5 MPGe

When Lexus announced the range for its first EV, the RZ 450e, the reception was less than enthusiastic. The company promised just 196 miles from a 71.4 kWh battery, but at the time, it touted the vehicle's efficiency as being more important than overall range.

In EcoRun testing, the car managed to beat its 102 MPGe (3.0 mi/kWh 20.7 kWh/100 km) rating by 18.2 percent. That's efficient, but its 3.6 miles per kWh (17.3 kWh/100 km) consumption figure was matched by some much larger, more powerful, and longer-range EVs.

Range Rover P440e: 25.1 mpg

The Range Rover P440e was by far the heaviest and bulkiest vehicle in this test, and it was also the most expensive, which explains how it manages an EPA range of just 48 miles from a 38 kWh battery pack. Using the combustion engine on the road, the Range Rover managed 25.1 mpg (9.4 L/100 km), 19.4 percent better than its 21 mpg (11.2 L/100 km) EPA rating. Crucially, that figure is 40 percent better than the similarly powerful V8 Range Rover is estimated to get on the combined cycle, so this big bruiser will save fuel compared to is petrol-powered siblings.

Mazda CX-90: 30.0 mpg

Mazda's first plug-in hybrid, the three-row CX-90, also had a solid showing in the road trip test. The CX-90 managed 30 mpg (7.8 L/100 km), 5 better than its 25 mpg (9.4 L/100 km) EPA combined rating, for a 20 percent increase. Mazda also offered one feature that no other vehicle in this test did: It had separate gauges to show instantaneous gas consumption and electric power use.

The same dial showed the average consumption for each power source. This made it easier to tell what power source you were using at any given moment. It also made hypermiling a lot easier, and I give the gauge more than a little credit for my own 39-mile-per-gallon (6.0 L/100 km) stint in the CX-90.

Hyundai Ioniq 6: 128.5 MPGe

Hyundai brought two Ioniq 6 sedans to EcoRun, and this showed two strange results: One car consistently returned higher efficiency, from a low of 10 percent to a high of 35 percent when the same legs were compared. The high result demonstrated just how much of a difference an individual driver could make. The lower result seems to be a difference between individual vehicles.

The only obvious difference between the two Ioniq 6 cars was that the one with less efficiency wore shiny paint versus the matte gray better-performing one. Some wind tunnel testing might be in order to find out more about the effect, but that's beyond the scope of this event (and shouldn't account for such a big difference anyway).

The efficiency of Ioniq 6's streamlined shape is immediately obvious at highway speeds—not from the gauges but from the sounds it doesn't make. Compared with the other EVs here, there is almost no wind noise.

To make the Ioniq 6 even more efficient, Hyundai lets you reduce maximum power output by picking the Eco drive mode. You can power down the front axle on dual-motor trims as well, which again makes it use less electricity.

The two Ioniqs averaged 129 MPGe (3.8 mi/kWh, 16.3 kWh/100 km), 25 percent better than the official estimate of 103 (3.1 mi/kWh, 20.0 kWh/100 km).

Hyundai Ioniq 5: 122.1 MPGe

Hyundai's boxier Ioniq 5 is estimated to hit 98 MPGe (2.9 mi/kWh, 21.4 kWh/100 km) on the EPA's combined cycle, just five fewer than the Ioniq 6 despite being much boxier and taller. On the road, the Ioniq 5, which shares its Eco drive mode tricks with the 6, averaged 122 MPGe (3.6 mi/kWh 17.3 kWh/100 km). Like the Ioniq 6, that's 25 percent better than its rating, showing that Hyundai might be being deliberately conservative in its range ratings.

Mercedes-Benz EQE 500 4Matic: 118.6 MPGe

The Mercedes-EQ EQE 500 4matic sedan is big and bulky, and it's as strangely shaped outside as it is luxurious inside. The EQE's odd shape clearly cuts through the air, helping it to deliver 119 MPGe (3.5 mi/kWh, 17.8 kWh/100 km) versus an EPA estimate of 94 (2.8 mi/kWh, 22.2 kWh/100 km). That's 26 percent better, just edging out the Hyundai Ioniqs.

Genesis Electrified GV70: 119.5 MPGe

Automakers keep chasing aerodynamic efficiency, but models like the Genesis Electrified GV70 show there's more to the formula than just the wind tunnel. The electric GV70 is wider and taller than the EQE, with more ground clearance, and those are great ways to ruin your total aerodynamic drag figure. Still, the GV70 beat the EQE and nearly matched the Lexus RZ with 120 MPGe (3.5 mi/kWh, 17.8 kWh/100 km). That figure is 31 percent above its 91 MPGe (2.7 mi/kWh, 23 kWh/100 km) EPA rating.

Kia Niro EV: 156.2 MPGe

Kia completely redesigned the Niro last year, and it once again kept the uncommon combination of EV, PHEV, and hybrid models. The unassuming Niro EV managed the highest overall score on this test with a 156 MPGe (4.6 mi/kWh. 13.5 kWh/100 km) average. It was second for beating its EPA estimates as well, 38 percent better than its 113 MPGe (3.4 mi/kWh, 18.3 kWh/100 km) window sticker figure. That shows the Kia could have managed 350 miles instead of the 253 miles the EPA suggests, which is very impressive.

Jeep Wrangler Unlimited 4xe: 28.2 mpg

What vehicle fared best compared with its window sticker figure? The one that's shaped like a brick and has a suspension lift and knobby all-terrain tires: the Jeep Wrangler 4xe.

The 4xe's window sticker shows that it should only manage 20 miles per gallon (11.8 L/100 km) on the EPA's combined cycle. In this test, the 4xe managed 28.2 mpg (8.3 L/100 km)—that's 41 percent better than suggested. It's the second-worst fuel economy score of the group, just beating out the Range Rover PHEV (and just behind the RX500h), but using half the expected amount of fuel in a seriously thirsty vehicle is an important accomplishment.

The Wrangler doesn't use any special tricks to improve its efficiency. It simply relies on how much more efficient electric motors are compared with a gas engine to boost economy from miserable to acceptable.

The defending champion

I said up top that the prize for EcoRun entrants was bragging rights, but there was more than just the knowledge of winning on the line. Each year, the winner gets a green jersey to rub in the faces of everyone else at the event. OK, we don't take it that seriously. The jersey is more like a trophy that sits in your closet instead of a shelf. This year, I took home the green jersey, becoming the event's first repeat winner and letting me blow my own horn just a bit. Until next year, at least, because there's always someone who tries a little harder.