Recently, I took a road trip in upstate New York, mostly on the interstate. My unscientific test showed that the Tucson’s gas mileage drops a lot when driving over 65 mph, even on mostly flat roads with some gentle hills.
I used adaptive cruise control for nearly the whole trip, with the AC on low. The car wasn’t loaded, and I was the only one in it.
I noticed that above 65 mph, the engine couldn’t generate enough power to charge the battery. Instead, all the power went straight to keeping the car at the set speed, so both the electric and gas motors ran about 90% of the time.
When I slowed down to 60-65 mph, the gas mileage got a lot better. It seems like this speed is the sweet spot for better mileage and still keeping up with the speed limit.
Now I understand why some people get low gas mileage when driving at 70+ mph. The engine can’t produce enough extra power to use electric mode or reduce how much the gas motor is used at that high speed.
HyundaiEnthusiast said:
This happens with every car that has a gas engine. Fuel efficiency drops a lot once you go over 65 mph.
I actually think it starts at about 45 mph. When I’m driving at 45 mph locally, I get amazing mileage even though my car isn’t a hybrid. Anything faster, and it drops a bit.
This has to do with turbulence. At a certain speed, the air around the car becomes turbulent instead of smooth, which makes drag worse. This point is different for every car but is usually why mileage drops at higher speeds. Things like air pressure, humidity, and wind speed can also affect it. You were probably in that range between 60 and 70 mph with your car on that day. The ‘best’ speed for fuel efficiency changes depending on the vehicle and conditions. Maybe someday cars will have sensors to show the best cruising speed, but for now, you just have to figure it out by feel.
70 mph works best for me (22 HEV SEL Conv). Being an SUV, it’s heavier and less aerodynamic than a sedan. At 70 mph, it can go into EV mode for short times, especially on straight, flat highways, and then switch to gas to charge the battery. This pattern helps keep mileage decent on long, flat drives. Above 70 mph, though, it mostly uses gas because the EV can’t handle those speeds alone. It wasn’t built for that. The PHEV version has a stronger electric motor, so it might be better for that.
@StevenMiller
I’ve heard the PHEV is less efficient because of the extra weight. I decided to stick with the hybrid until my charging options get better.
barabra said: @StevenMiller
I’ve heard the PHEV is less efficient because of the extra weight. I decided to stick with the hybrid until my charging options get better.
If you mostly drive short distances like I do, the PHEV is better because you can use EV mode all the time. For longer trips, or if the battery is dead, you still have gas.
@Ameliascarlet
For me, the extra cost isn’t worth it. I only drive about 5,000 miles a year, and charging is tough and expensive for me. If you can charge at home, it’s fine, but then a full EV might be better.
