A plug-in hybrid electric vehicle, or PHEV for short, is more or less a stopgap between a traditional gas car and a full-on electric car. But that’s ok, because not everyone is ready to make the transition to an EV, so a plug-in hybrid could make for the perfect alternative.
Thanks to a larger high-voltage battery and a more powerful electric motor compared to a traditional hybrid, a PHEV can deliver significantly better fuel economy and somewhere between 30 and 50 miles of electric range for the daily commute.
However, because there’s still a gas engine under the hood, some might be tempted to just treat it as a traditional hybrid. And it will work as one, but that’s not the point of a PHEV. In fact, one study revealed that most plug-in hybrids never get plugged in, negating the benefits from the get-go.
To make the most out of a PHEV, one should think of it as two cars in one. It’s an EV and a gas car, and that comes with some peculiarities. I found this out on my own, as the owner of a particular Swedish plug-in hybrid wagon.
So here I am now, trying to pass on what I’ve learned from driving several thousand miles behind the wheel of my PHEV.
Always Be Charging
This is the most important piece of advice for any PHEV owner. You probably bought a car with a plug, thinking it would lower the running costs–I know I did–but it can only do that if you regularly top up the battery.
Carrying around a depleted battery will put unnecessary stress on the gas engine, leading it to drink more fuel than it should. This means the fuel efficiency of a PHEV that never gets plugged in will be marginally better than the same car without a big battery. In some cases, it could even be worse, depending on the car.
So plug in every time you can—it will make a huge difference. With a full battery and a full tank of gas, the average fuel consumption will be at least 25% lower than just doing the same trip with an empty battery. In my case, the average fuel economy with an empty battery and a full tank is about 30 miles per gallon. Doing the same trip, but starting with a full battery, upped that figure to 40 mpg.
Still, doing long journeys is rare for me, so I usually only run on electricity, which has dramatically cut the fuel costs, even compared to a smaller and much lighter Volkswagen Golf. I now pay about 50% less for fuel, including electricity. After about 4,500 miles, my overall fuel economy is 60 mpg.
Find The Right Driving Mode For Each Scenario
Each plug-in hybrid has different driving modes, and they’re not there just for show. Usually, PHEVs have a pure electric mode, a hybrid mode and something that keeps the gas engine running all the time. But that’s not all, because each driving mode can have some hidden benefits that, at the end of the day, will result in lower costs.
Take my Volvo V90 T8. (Or any other Volvo PHEV made after 2022.). In Pure mode–that’s the all-electric one–the car will coast when I take my foot off the accelerator pedal over 25 miles per hour. If you were to ask someone from Porsche about this behavior, they would tell you that coasting is the most efficient way of driving an EV.
And I agree–as long as you’re in the right scenario. On long stretches of road, where you might encounter slight inclines, coasting is the best way to get the most range, both in PHEVs and EVs. You just take your foot off the go-fast pedal and the car will effortlessly move while using barely any energy from the battery.
However, regenerative braking also benefits. This uses the electric motor to slow down the car and put energy back into the battery. It kicks in when using the default hybrid driving mode, but also when pressing the brake pedal, before the friction brakes do their job.
For more regen braking without having to touch the brake pedal, many PHEVs have a "B mode" on the transmission, which does just that. That will activate, or dial up, the regen braking system.
On a long trip, I pick the best driving mode for the area I’m in. Usually, I set off with my Volvo in Pure mode, which lets the car use more energy from the battery compared to the Hybrid mode. Then, when I get to steep descents or inside towns, I switch to B mode to get the most regen without touching the brakes.
Every drive is different, so experiment with what your car offers. On one occasion, I managed to squeeze out 71 miles of electric driving out of my V90, despite Volvo claiming just 54 miles of electric driving in combined conditions on the WLTP cycle. And that was with five people inside and a full trunk.
You might be surprised to see that the high-voltage battery is capable of delivering more electricity than the manufacturer claims. I know I was.
Don’t Forget About Maintenance
EVs are known for their low maintenance needs compared to combustion cars, but PHEVs still need to be cared for like a gas vehicle. Even though the engine will barely run if the car is regularly plugged in, the oil still needs to be changed at the manufacturer's recommended intervals–or sooner. Even if the car sits still, automakers still recommend changing the oil every year.
Then, there’s the automatic transmission that needs to be kept in tip-top shape. While some carmakers say their transmissions are “sealed for life,” that usually means you don’t need to change the fluid as long as you have a warranty. Once that runs out, you’re on your own. And if you want to keep a car for a long time, the gearbox oil will have to be replaced at some point, with most mechanics recommending once every 40,000 to 60,000 miles.
The same goes for the differentials, especially if they’re driven by an electric motor. This is in addition to the usual cabin and air filter replacements, wiper blades and tire rotations.
