I drive a manual transmission car and I find my mileage to be comparable if not lower to an automatic transmission car. While activating cruise control, my mileage rises by a few kms because of this I have always wondered which transmission for my next car would be the best, considering mileage to be an important factor.
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Automatic transmissions use a torque converter, and there is a small loss in efficiency there, as compared to a manual gearbox which has a mechanical clutch. However, modern automatic transmissions use a lockup plus have had many technological advances and are very efficient compared to the old days.
For the typical driver, there’s very little difference in fuel consumption between the two. And for someone who loves revving the engine, an automatic might actually give slightly better fuel consumption because it will shift to a higher gear earlier.
With a good driver, manual transmission will give you slightly better fuel consumption because the driver is selecting the right gear for the speed/load/grade and also shifting efficiently.
I would personally recommend an automatic (assuming its a modern car brand/model), especially if you drive in a city with a lot of traffic because the overall difference is minimal, as compared to the hassle of shifting constantly imo.
Well, it ought to be obvious that a manual transmission is far more prone to the vagaries of how the driver drives the car than an automatic is. I’m sure that, driven properly, a manual car can easily do better than an automatic, if nothing else than because such a gearbox is usually lighter and thus saves a little bit of weight on the car, saving some fuel as well.
If the actual transmission technology and engine is the same, then automatic transmissions always win the efficiency game, unless the software used is ridiculously poor or you’re driving in extraordinary terrain.
The reason is simple: Automatic transmissions will keep your engine in the sweet spot of revolutions per minute, where power vs. consumption is optimal. If you’re getting slower than your current gear can support optimally, the transmission will automatically shift down, and vice-versa. In a manual transmission car, the driver is controlling all of these decisions. Even if the driver is considering these aspects (which they rarely are), they would still need to actually do the shifting of gears at the perfect times every time to beat the automatic transmission. And most drivers are too lazy for that, or they can’t shift gears at the perfect time because they are in the middle of a turn and need both hands at the wheels, or they have the radio so loud that they don’t realize the revolutions per minute are too high etc. Add to that, that the ordinary driver can’t shift gears nearly as fast and flawlessly as a modern automatic transmission can.
The only advantage a manual transmission car has in terms of mileage (apart from a little bit of weight reduction) is that the driver can anticipate the near future, while the automatic transmission can’t (yet). So if the driver knows that more power will be needed shortly, they can shift down before accelerating, which saves a little bit of fuel. And if the car is going downhills or will have to break soon, the driver can use the shift-down to add some breaking power without sacrificing fuel to idling.
So overall, unless you compare cars from the 1980’s or you’re regularily driving in extreme terrain, automatic transmissions are definitely more fuel efficient.
Edit: That being said, I’m a huge fan of manual transmissions and I have been driving manual shifts almost exclusively for 15 years. I have now switched to automatic transmissions and find it so relaxing, even if the loss of control can be felt at times, especially when maneuvering in narrow spaces or at steep hills.
The blunt truth: Driver skill/style is 10x more important than transmission.
If fuel consumption is a priority:
1) Drive at the speed limit. EVERY car (other than sports cars perhaps) will be a LOT more fuel efficient at 65mph or less. This can easily save 10-15% on fuel consumption on highways.
2) Accelerate gently and anticipate slowing down and coasting to more gentle stops. In stop and start traffic, this again easily saves 5-10% on fuel consumption.
3) Maintain tire pressures, tire alignment and maintenance of engine.
The differences in fuel consumption between a modern automatic transmission and a manual are small, if any, if a driver practices the above.
This is a very easy thing to test. Drive slower and less aggressively and monitor mileage. Do the comparison.
A modern automatic transmission is going to be pretty much the same as a manual transmission driven by a competent driver. A modern continuously variable transmission (CVT) will perform better. Most electric cars have a single gear and are more efficient still.
Really, your mileage will ultimately be more dependent on how fast and aggressive you drive than anything else.
We are speaking about small fractions. Form best to worse:
1 superb driver with manual.
2 robotic shift (clutch and gears but automated)
3 normal driver with manual
4 automatic with torque converter and gears.
But mind that the drive style is way more a factor compared to the above list. Above,we are speaking about 1% differences.
An automatic with torque converter is maybe 1-2% more thirsty than a superb driver with a manual set.
to be considered: we don’t always focus that much on gears, so the manual gears will have different result in different days. Also, the manual advantage exists only if the road allows for it. Some terrains don’t give you any advantage to exploit with manual. While manual is for example very very good in mountains, its not so much if a help in traffic jams, where the difference between a manual and a torque converter is that the manual will wear down more (clutch expecially). Torque converter may be slightly less efficient but will give the smoothest ride of all, while also being the easiest.
So, don’t focus only on mileage when choosing transmission. Reliability, long term costs, road type, congestion, and your drive style; all of this important in the choice.
When you say mileage I think of longevity. Manual trans and automatic trans are both reliable, as long as you don’t shift into a lower gear while in a high RPM. CVTs are pretty much unreliable,though E- CVTs that get used in hybrids such as the Prius use physical Planetary gears rather than a system of belts and pulleys like a traditional CVT. e-CVTs are more reliable than traditional transmissions also
For 95% of people and 95% of driving, a modern automatic is the right choice.
In the old days, there was about a 10% loss of mileage with a three-speed torque converter automatic. Modern autos have more gears, torque converter lockup and presumably other efficiencies that reduce this difference significantly.
They also work much better with all of the modern technologies in todays cars.
If you are looking at a simple, light sports car or hot hatch which is driven mainly for pleasure – that’s when I would consider a manual. It does give more engagement – it’s simply more fun.
The modern thing is a very complicated device called a twin-clutch automated manual gearbox; called DSG in Audi, PDK in Porsche, with other manufacturers having their own names. Unlike regular automatics, they are both faster and more economical than manual transmissions. But much more complicated and with the risk of expensive repairs. Look for a long warranty.
CVT transmissions are different altogether, quite efficient, not hugely complicated, generally boring as fuck to drive.
If you know what brand of car you are looking at, people can give more informed recommendations based on what that manufacturer did well. If you don’t care that much about the brand, then I would just say get whatever is the most popular fitment for the model you choose.
Manual transmissions used to be more efficient than automatics–auto transmissions’ torque converters slipped, and had just two or three speeds. That changed some years ago–auto versions of vehicles get better mileage than manuals now. Better design, more speeds now, I suppose. CVTs might be all right for city and flatland use, not so much for mountain driving. Toyota has an interesting variation on the CVT–first gear is conventional, then switches over to the CVT. My experience with CVTs is industrial–CVTs are just a type of variable speed sheave. Not a big fan.
Neither. The popularity (by manufacturers) of CVTs (Continually Variable Transmissions) is due to their being able to continuously adjust to run the engine at a more efficient speed.
I don’t think the consumers really want them as they have a bad rap (earlier ones were failure prone), however they improve advertised efficiency which is good for the manufacturer.
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