Maximizing fuel efficiency: shifting to higher gears could save you 30% at city speeds
Car manufacturers frequently recommend using higher gears as they're more fuel-efficient. Gear change indicators and engine characteristics affirm this. However, not all drivers adhere to these suggestions. Some argue that using higher gears unnecessarily stresses the engine, increasing fuel consumption at lower gears. But is this accurate? Let's explore.
2:24 AM EST, January 27, 2024
A car's fuel consumption depends on several factors. The primary ones influenced directly by the driver are engine revolutions, determined by the selected gear and speed, and engine load, which is dependent on the pressure on the gas pedal. The chosen gear affects engine revolutions at a specific speed, while the engine load is directly reliant on the position of the gas pedal.
Is it possible for a car to drive uphill with a low load and downhill with a high one? Indeed, it is. It largely depends on the way the driver operates the gas pedal. Nevertheless, if a driver aims to maintain a consistent speed, engine load will be higher when encountering steeper road slopes, heavier cars, stronger winds, or higher speeds. Despite these variables, the driver still has the flexibility to select a gear that reduces the engine's workload.
Some drivers prefer to keep the engine operating in the middle of the revolution range and stay in lower gears for more extended periods while others prefer higher gears and fewer revolutions. If the engine revolutions are lower during acceleration, the engine load increases instead, and the gas pedal has to be depressed further. Efficient driving requires maintaining these two parameters at a level that ensures optimal car efficiency. Essentially, the goal is to strike the right balance between load and engine revolutions because increasing these parameters elevates fuel consumption.
The Autokult.pl editorial team conducted a test over a defined distance at three different speeds. The results were unequivocal: higher revolutions, meaning lower gears, result in increased fuel consumption. The differences were substantial, particularly at higher mileages.
The vehicle used for the tests was a Suzuki Baleno with a naturally aspirated 1.2-liter DualJet gasoline engine. The car was driven at three typical speeds for Poland's national roads—31, 43, and 56 mph. Fuel consumption was confirmed in the 3rd, 4th, and 5th gears, except for the 3rd gear and speeds of 43 and 56 mph since driving in such a manner would be impractical. Here are the test results:
At a speed of 31 mph:
- in 3rd gear (2200 rpm) fuel consumption was around 60 mpg,
- in 4th gear (1700 rpm) fuel consumption was roughly 73 mpg,
- in 5th gear (1300 rpm) fuel consumption was about 84 mpg.
At a speed of 43 mph:
- in 4th gear (2300 rpm) fuel consumption was approximately 60 mpg,
- in 5th gear (1900 rpm) fuel consumption was close to 65 mpg.
At a speed of 56 mph:
- in 4th gear (3000 rpm) fuel consumption was around 51 mpg,
- in 5th gear (2400 rpm) fuel consumption was about 56 mpg.
Based on these results, we can deduce that fuel consumption differences between the 4th and 5th gears at typical road speeds (43-56 mph) are minor, ranging from 8-9%. However, using higher gears at city speeds (31 mph) results in considerable savings, ranging from a few to nearly 30 percent, depending on the driver's habits. Many drivers often use lower gears in the city and downshift when traveling through towns on the route, intending to maintain good engine dynamics. They, however, may not realize the significant impact this has on fuel consumption.
It's important to note that there are exceptions. The latest vehicles come equipped with multi-gear automatic transmissions, which often engage the 9th gear on highways. Regrettably, extremely low gears aren't always efficient. At an allowable speed of about 87 mph, they occasionally do not engage or rarely do, and at significantly higher speeds of about 99-112 mph, they resist engaging because the load is too much. As a result, manual gear engagement increases fuel consumption.
Scenarios like mountain driving may warrant the use of a lower range of gears in heavier cars with an automatic transmission. Modern automatics typically try to sustain low revolutions, even at the cost of excessive engine load. Unfortunately, this doesn't correspond to lower fuel consumption. In challenging conditions, cars with many-geared transmissions often consume less fuel, for instance, in sport mode.
