Cars

Are miles-per-gallon claims realistic for hybrid vehicles?

John Paul, AAA Northeast's Car Doctor, answers a question from a reader who’s skeptical of manufacturers’ mileage claims.

2022 Toyota Prius Nightshade. Toyota

April 12, 2022

Q. Are the miles per gallon listed by the manufacturer for their hybrid models realistic, or would they fall short in everyday driving? In other words, what kind of driving behavior would a driver need to follow in order to meet or get close to the estimates touted by the car manufacturers in the vehicle descriptions?

A. I have driven many hybrids and found the mileage very realistic. Like any vehicle, mileage is mostly controlled by the driver. Quick starts and high speeds will affect mileage. If you drive reasonably at the posted speed limit, that mileage is easily attainable and sometimes exceeded. Drive a Prius at 80 miles per hour and you’ll never get 50 miles per gallon.

Q. I own a 2015 Ford F-150 with the EcoBoost engine and only 9,300 miles on it. When stopped at a red light the engine would shut off as it is supposed to then restart when the gas pedal was applied. Now, it no longer does that. It was checked by a Ford dealership mechanic, but he could find no reason for this.

A. No one should know more about your Ford truck than a Ford technician. For the auto-stop system to work certain criteria need to be met. These include engine temperature, engine load (air conditioner on/off), trailer towing, brake light switch, and charging system operation. It is possible that with such low mileage on a seven-year-old truck the battery state of charge is low enough that the computer won’t signal to shut off the engine. The first step in diagnosing this problem would be to check to make sure the battery is at a full charge of at least 12.6 volts.

Q. I have a 2000 Toyota Land Cruiser and the air conditioner button is always on when the heat is turned on. It was supposed to turn off and on if you press the button, but it is always on. It appears to just be stuck. How do I make it properly functional again?

A. The climate control system in your Land Cruiser has a diagnostic mode and the diagnostic test should be performed first. The problem could be as simple as a shorted switch or relay, but a diagnostic inspection is the first place to start.

Q. My 2018 Volkswagen Jetta has only 12,000 miles on it. I’ve owned it since 2016 and put maybe 7,000 of those miles on myself. Recently I’ve noticed that when I start the car, the dashboard display (odometer and tachometer) do not light up. Eventually, they will light up, but may (or may not) go back off for a while. I can get them to light by switching on headlights and, yes, it does not appear to affect the daylight running lights. Most recently, I found that if I lower the driver’s side window the lights will come on, but they go off as the window is closed! The problem seems to be related to moisture, but I haven’t been able to pin it down to the point where I can tell a service tech what’s happening.

A. I would suspect some sort of poor electrical ground. At this point a series of voltage drop tests need to be performed as well as a basic test of the battery. When putting the window up and down you are putting more of a load on the electrical system, causing the voltage to vary?

Q. I just bought a 2021 Jeep and would like to know if there is a way to get better fuel mileage. It has the V6 engine, and I am getting around 12 to14 miles per gallon in the city and at best 20 miles per gallon on the highway.

A. I would expect to see about 15 to 16 miles per gallon around town and 22 to 24 miles per gallon at a steady 60 miles per hour on the highway. Winter gasoline has less energy which can cause you to lose up to 10 percent of your fuel economy. If your Jeep has a remote starter and you use that regularly, fuel economy can be reduced dramatically. At this point, check and inflate the tires to the correct specification and look at your own driving habits. Fuel economy can be improved by driving reasonably – easy on the gas and brake and staying at the speed limit. Depending on the mileage on your Jeep, it can take up to 10,000 miles for the engine to fully break in.

John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your car question to [email protected] Listen to Car Doctor on the radio at 10 a.m. every Saturday on 104.9 FM or online at northshore1049.com.