I got into a 2025 Toyota Hybrid 4Runner the other day and looked at the average mileage reading on the dash – 19 miles per gallon. I was amazed by how low it was. A Google search showed that the rating for this vehicle’s miles was 23 mpg city, 24 mpg highway and 23 mpg combined, whereas the Standard 2.4 liter Turbo (4WD) was up to 19 city / 25 highway / 21 combined mpg.

With the complexities and expense of a hybrid, this is not enough of a fuel saving to justify the hybrid.

Unless a lightweight, smaller vehicle like a Prius, which gets 57 city/56 highway (57 combined) mpg, fills your needs I would recommend a turbo-charged engine. The gasoline engine has become very refined and, with the addition of a turbo, manufacturers can get the horsepower of a V8 and the miles per gallon of a 4-cylinder. The Ford Bronco has a 2.0 liter EcoBoost engine that produces 250 horsepower with gas mileage of 21 mpg city / 27 mpg highway, compared to a 1969 Ford Mustang with a 351 CID (Cubic Inch Displacement) V8 (5.8 liter), which produces 250 horsepower with gas mileage of 10 to 14 mpg in combined city and highway driving.

So what exactly is a turbo? To get the most power from an internal combustion engine you need to fill each cylinder with as much fuel and air as possible. On a non-turbo engine this is accomplished by the piston sucking the air in as it travels down the cylinder.

A turbo acts like a compressor and forces more air into the cylinders. This is accomplished by the exhaust gases leaving the engine spinning a turbine blade that is attached to another turbine blade on the intake side that forces the air into the engine. The faster the engine is accelerated, the faster the turbine blade spins, generating more air to be forced into the engine. This process does not rob any energy from the engine itself, so it gives nothing but better performance — whereas other processes like superchargers are run by a belt that is turned by the engine, so it takes power away from the engine.

There are several sensors on the engine, ranging from temperature sensors to camshaft and crankshaft positions and fuel pressure sensors. The engine control unit uses this information to regulate the fuel supplied to each cylinder. Each cylinder has a fuel injector that forces fuel directly into the cylinder, called Direct Injection. The exhaust also has an oxygen sensor that checks how efficiently the engine is consuming the fuel, and adjustments are made immediately.

The next step is to take as many loads off the engine as possible. With electric power steering the power steering pump is no longer a load on the engine. Transmissions have also come a long way. Constant velocity transmissions (CVT) and 6-10 speed automatic transmissions keep the engine in the most efficient rpm (revolutions per minute) range. This is one reason manual transmissions are so rare these days. The most efficient rpm range for a gasoline engine is 1,500 to 2,500 rpm. Human interaction with the transmission does not accomplish this very well.

Some day electric vehicles will take over the roads; until then, smaller, more efficient engines will have to fill the bill.

Doug Carter is the owner of Carter’s Auto Service, Inc. He’s been in the auto service business since graduating from Gorham High School in 1981.