Does your transmission have an impact on your vehicles gas mileage?

by Luke Wilhoit Consultant

The engine inside your vehicle produces the power needed to go down the road, but the transmission is what sends the power to the drivetrain. The transmission mounts directly to the engine and transfers the horsepower and torque produced at the crank into usable horsepower and torque at the drive wheels.

The amount of horsepower and torque produced at the crank typically drops by about 10 percent to 15 percent via the mechanical connection between the engine and the drive wheels. The transmission and drivetrain always sap some of that power, which is an example of how a transmission affects power delivery and resulting fuel economy.

Manual Transmissions and Their Impact of Fuel Economy

The manual transmission is the first successfully  mass-produced transmission and came standard in vehicles for several decades. The driver manually engages the clutch with his or her foot and uses a lever to manually change gears with one hand. The manual transmission enables the driver to choose when to change gears and keep it in a particular gear when preferred.

That ability to strictly control the gear changes makes the manual transmission especially prized among highly skilled race car drivers who are trying to get the maximum performance. It also is lighter than an automatic transmission, which means more power to weight. Skilled drivers likewise can use the manual transmission to maintain ideal performance and traction to get the best possible fuel economy.

A manual is especially beneficial when driving conditions are bad due to rain or snow and traction is harder to obtain. The manual transmission generally is simple to maintain and sometimes requires a new clutch to rebuild it after many years of good service. Its relative ease of maintenance and affordable rebuild costs make the manual more affordable than an automatic, but very few new models come equipped with a manual.  

Automatic Transmissions and Their Impact of Fuel Economy

A good example of a modern automatic transmission is GM’s 6-speed 6L90 transmission used in General Motors vehicles across many make and model lines. The 6L90 has six gears that enable it to crawl from a slow start and increase the gearing and speed up through the sixth gear, which generally works as an overdrive gear to maintain highway speeds.

The gears are longitudinal gears, which means they are aligned horizontally, and clutches enable gear engagement and changes. Many early automatic transmissions had just three or four forward gears plus a reverse that handled general duties but would sap power and fuel economy. A hydraulic system automatically changes gears when it detects significant changes in pressure and mostly works to find the ideal range.

The addition of more gears over the years resulted in the six-speed automatic transmission becoming a standard version for many years. Current automatic transmissions often have 10 speeds to provide the best power transfer and greatly improved fuel economy. When the motor can maintain highway speed while using gas at about the same rate as when idling, you get much better gas mileage. 

CVT Transmissions and Their Impact on Fuel Economy

Many current models use the continuously-variable transmission, which typically is referred to as a CVT transmission. Unlike the manual and the automatic transmissions, the CVT does not have gears. Instead, two pulleys change in width as the engine needs to deliver more power to the drive wheels. One pulley connects directly to the motor while the other connects between two and four drive wheels.

The continuously variable width causes one pulley to get wider as the other becomes narrower with a durable flexible belt connecting them. The automated nature of the continually adjusting pulleys work similarly to an automatic transmission but without gear changes needed to adjust power delivery to the drive wheels.

Unlike a manual or an automatic, the motor does not rev higher as the RPMs increase until changing gears. It provides a smoother power transfer and delivery to the drive wheels. More efficient power transfer adds up to better performance and increased fuel economy over a manual or automatic transmission.

Which Transmission is Best?

Choosing the best transmission for your vehicle mostly depends on your intended driving purposes. If you like a sports car with a classic driving feel, the manual is your best option – unless fuel economy matters. Then you likely would opt for an eight-speed automatic.

If you are going to haul a lot of heavy items, a manual also might work best, which is why tractor-trailers use them almost exclusively. But if you are looking for the best combination of performance and fuel economy in a daily driver, then the CVT unit likely would be your best option. 

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About Luke Wilhoit Freshman   Consultant

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Joined APSense since, February 15th, 2021, From Buffalo, NY, United States.

Created on Feb 16th 2021 15:37. Viewed 430 times.


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