Myth-Busting: Manual transmissions are more fuel efficient
This one relates to fuel economy with many holding to the belief that a manual is more fuel efficient than the same car with an automatic. So, are manual transmissions more fuel efficient?
UNFORTUNATELY, the manual transmission itself will soon become a myth. See, more on and more young drivers are opting for an automatic rather than shift gears for themselves. And, so car makers are responding. Indeed, you can almost count on two hands the amount of manual cars you can buy aimed at younger drivers. Sure, some makers still include them in the line-up to chase that ‘price tag’ that gets used on billboards and TV ads, but very few people are actually buying an entry level car with a manual. But I digress.
Onto today’s myth…and that is, that a manual transmission is more fuel efficient than an automatic transmission. But, unlike some myths, this one isn’t as easy to bust as you might think.
See, back in the old days it was a given that a manual transmission was more fuel efficient than an automatic transmission. And that’s because the automatic generally had less gears (there’s more to it than that, like the torque convertor, but gearing is one of the key reasons). This meant, a three- or four-speed automatic was generally revving higher at any given speed than, say, a five- or six-speed manual.
But those days are gone. Automatic transmissions often now run more gears than their manual equivalent (up to nine vs six-speeds) and they’ve spawned new classes of much more efficient automatic transmission, like CVTs and dual-clutch transmissions (which generally offer more gears than their manual equivalent). And it’s this and other features like locked torque convertors (that no longer slip) and just generally more advanced mechatronics that have made the gap between the two transmission types much smaller.
For instance, if we look at the Hyundai i30 with 2.0-litre four-cylinder petrol engine the difference, on the combined cycle, is 7.3L/100km Vs 7.4L/100km, manual vs automatic – both are six-speed units. If you consider the i30 diesel the gap (manual vs automatic) is a little wider at 4.5L/100km Vs 4.7L/100km. Then, the i30 with a turbocharged 1.6-litre four-cylinder petrol and it’s a dead-heat between the six-speed manual and the seven-speed DCT. Move away from a small car to a 4×4 dual-cab Ranger PXII and the 2.2-litre four-cylinder turbo-diesel mated to a six-speed manual drinks 6.8L/100km (claimed combined) while the automatic drinks one-litre more at 7.8L/100km.
In these cases, the major difference in fuel consumption is when you compare a manual transmission with a traditional torque convertor automatic… change up the automatic transmission type, like the dual-clutch transmission in the i30SR and there’s no difference in the fuel consumption (claimed).
And then there are those automatic transmission types that are radically more fuel efficient than their manual equivalent. Like the CVT. Take the Subaru WRX, for example, it offers both a six-speed manual and CVT option…the manual (combined claimed) drinks 9.2L/100km while the CVT drinks 8.6L/100km. And it’s the same story for the Toyota 86 which, in manual form drinks 8.4L/100km and in automatic drinks 7.1L/100km (claimed combined).
So, while I’ve only grabbed a small sample size and while, on paper, manual transmissions are generally more fuel efficient than the automatic equivalent (although not in all, like the Toyota 86), the gap between the two transmission types is so small that I’d suggest it really is a myth that manual transmissions are more fuel efficient. Especially when you through CVTs and DSG (DCT) transmissions into the mix, which are either as efficient or more efficient than a manual 
transmission.
What you can more easily argue is that a manual transmission vehicle is cheaper than an automatic, in some cases the difference can be up to $2000; and that’s a lot of extra money to spend on fuel in the manual.
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10 Comments
Except I still prefer a torque auto over cvt or dsg. Why should I have to re learn how to drive to avoid nasty consequences of driving a cvt or dsg? Love the extra control of a manual but prefer the ease of driving an auto
Yep, I get that. For me, though, a DSG is a good transmission; you’ve just got to get used to driving it like a manual – sort of. Isaac
The thing with dual clutch is you have to let go of the brake pedal 1st so the engaging clutch reacts so you get that lurch feel but you have to be quick to provide accelerator input otherwise the preloading clutch will start to slip and over heat, so for city stop start driving it’s not the best as the transmission is constantly trying to preload the gear it’s trying to guess the driver needs (hesitation feel), great for the race track not so good for metro driving, oh wet we now that a wet clutch type is better than dry clutch type.
CVT is fine, sloppy but fine if left alone in D, that said if you drive it in step mode (manual mode) it can be fun, it’s like a manual without a clutch as the engine is forced to rev and stay at those revs, get a CVT above 120km/h and use manual mode from, what ever ratio simply I guess yiu would have say “step down” afew ratios it basically rev matches and holds those revs, faster than a Dual clutch or a manual as there is no brake in accelration whereas a Dual Clutch and torque converter will be forced to upshift the CVT will hold the step ratio, it can catch you out if your not careful.
Torque converters are dumb in that they can only go up or down in sequential order, whereas a Dual clutch will do that as will a CVT but the advantages of torque converter are also why it’s still the best transmission on offer, especially with Ford (and GM) offering super fast 10-speed ones with close ratios, as close to a CVT as you can get without the need for a super low final drive to help get off the line.
Manual is manual, great for trucks and race cars but useless for the vast majority of cars today, you would be better off with a torque converter auto nowadays for off roading.
I feel DSG transmissions are pretty pointless in city cars such as Golfs. They are just demonstrably worse at crawling in traffic, which is going to make up a large chunk of the driving these cars do. Sure, they will shift 50 milliseconds faster than a torque converter auto, but that is largely irrelevant for most driving. They certainly have a place in sports cars, but I feel the disadvantages (especially the expensive clutch pack replacement when they inevitably wear out after prolonged city driving) outweigh the advantages.
For the manufacturer’s official readings that may be so.
But, with either transmission, the way they’re driven is paramount. Driving a manual for economy will always beat an auto driven with the type of jack-rabbit starts most drivers use – and vice-versa.
But the transmission has to be a good one. My test-drive of a DSG last year was woeful. I took it into a parking situation, 3 point turns, tight traffic – the thing would sit there – then suddenly lurch. I felt it was so unpredictable as to be dangerous – and handed it back. My wife would have refused to have driven it, it was so bad. It was a pleasure to get back into my manual FIESTA.
Hi Alan, yes, and for the article that’s all I can deal in. What vehicle were you test driving… sometimes DSGs can be a little clumsy at low-speed. The trick is to be on the brake fully when you’re changing from reverse to drive and then hold a moment before releasing the brake… I know you probably don’t want to do that, but driving a DSG can take a little brain-training. It’s certainly quicker when up and running than either a manual or a conventional automatic. Cheers Isaac
’twas a Golf Wagon – great layout (except the crazy CD in glovebox). 91TSI – was a 7, not 7½. It was in stop-start traffic which was the worst, it would come to a stop and re-starting just did nothing, gradually increase revs and eventually it would move – like a tiger pouncing. It happened first while the salesman was driving, and AEB caught it before he hit the back of the car in front – he didn’t tell me what the problem was. But I soon found out. No wonder he wanted me to go on their established DSG friendly tour, but I pulled off to a side street, into a carpark – then back into the stop-start traffic. Nope. As I said, if I gave it to my wife to drive – she’d send me back after a day.
I’d driven a few other cars about the same time, none were anything like this poor. I didn’t like the CVTs particularly, but at least they drove fairly well. The proper autos (Cerato, Focus etc) were much better.
I can drive a Manual smoother than VW can a DSG.
VW’s DSG seems to be on the skids also because their new 8 speed torque converter transmission will give a lower consumption figure……and if they were to dump their manual and dual mass flywheel they could give a competitive warranty.
“The manual transmission itself will soon become a myth.”
You do realize that 80% of cars in Europe still use manual transmissions – right?
As for the main myth, real-world testing by organizations like Consumer Reports and Motor Trend still often give an advantage to manual transmissions – even when official mileage estimates rate them lower than the same car with an automatic.
Government mileage testing of manual transmissions tends to use inefficient shift points, with the result that in real-world driving, cars with manual transmissions can significantly exceed their rated mileage. In a 2015 AAA study of real-world fuel mileage, cars with manual transmissions exceeded their EPA ratings by a bigger margin (17%) than any other powertrain type other than diesels.
Anecdotally, I’ve compared two pairs of nearly identical older Subarus over about 12 years – in both cases, the same model except for the transmission. In both cases, the EPA mileage ratings for the automatic and manual versions were identical – but I consistently was able to achieve 15-20% better mileage with the manual version. The difference in cold temperatures – even with newer transmissions – is still more pronounced.
Completely agree, the idea that automatics get better mileage the real myth. Anyone with a decent understanding of how an automatic transmission works should understand that a manual is more efficient.
Autos use hydraulic power to shift and hold the transmission into gear, this hydraulic power is provided by the engine, a manual uses energy from your arm to shift and a detent hold it in gear. The torque convertor adds more losses to the system, even a locking converter than a clutch does, especially so when the vehicle is stopped. There’s more components, like clutch packs, actuators, valves, drums, bands, a pump and significantly more gears which adds friction. The moving components in an auto overall are heavier, meaning more inertia has be to overcome to move said components.
Here’s another clue, almost all autos need an external cooling solution while most if not all light duty manual transmissions do not. This is because there is more energy being turned into heat in an automatic transmission, translating to more fuel being burnt to do the same amount of work.