Which has better fuel economy: manual or automatic? - 2014+ Jeep Cherokee Forums
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post #1 of 13 (permalink) Old 02-23-2017, 10:50 AM Thread Starter
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Which has better fuel economy: manual or automatic?

From what i have read same car, same driver, equal distances and speeds , automatic transmission has fuel consumption by 8-10% Higher.

What is the technical reasons behind this?
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post #2 of 13 (permalink) Old 02-23-2017, 11:00 AM
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It depends on the vehicle and drive train. Major reasons are computer controls, synthetic oils, more gears, torque limiting / fuel management via port injection and direct injection. Start/stop. And other factors.

That said, I still prefer to shift myself.
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post #3 of 13 (permalink) Old 02-23-2017, 11:16 AM
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IN EPA tests automatic will usually win.

In real life it depends on the driver.

you can drive an automatic "wrong" too.

MT doesnt have as wide a gear ratio so theoretically the automatic should always win.
MT is more efficient but with lockup torque converter its very small difference once upto speed.

All things are never equal so its really down to the driver, the terrain/traffic etc.

In Previously vehicles I routinely beat the sticker MPG with the stock tires easily.(I had MT's)

Driving 5mph faster or slower will be more fuel economy difference than stick vs auto.

Then again if you get something like the cruze ECO, or diesel 6mt I have heard the stick is better.

There are plenty of reasons to choose either.. I wouldnt let MPG push me to one or the other.
Pick what suits you.

I love MT, but it is worse offroad. Torque converter allowing creeping/stopping is a major advantage.
Offroad can also be extremely hard on your clutch.

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Last edited by Rand; 02-23-2017 at 11:19 AM.
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post #4 of 13 (permalink) Old 02-23-2017, 11:19 AM
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There's more friction in an automatic due to the clutch packs that aren't present in a manual, but the biggest culprit is the torque converter. Before computer controls in the 80s, only a few converters locked. Even locking converters today lock up under specific conditions. While unlocked, a converter is like a manual transmission clutch that is slipping.

The newest automatics with many gears and very advanced programming minimize the losses to the point the difference in fuel economy compared to manuals is very low.

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post #5 of 13 (permalink) Old 02-23-2017, 11:45 AM
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Funny no one mentionned CVTs. Or DCTs. Both more efficient than the 2 older technologies.

A good read here : http://www.roadandtrack.com/car-cult...-the-best-one/
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post #6 of 13 (permalink) Old 02-23-2017, 12:27 PM
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Many CVT and DCT have/had massive issues that make the early issues with our 9 speed seem extremely minor.

Try crawling in a parking lot with a DCT.. lots of funky action..

"Wet" DCT seem to be much more reliable than "Dry" type.

Just look at that DCT disaster in recent ford Focus for example.

A wet type would be VW and theirs are pretty reliable for a dct except for the very pricey maintenance.


CVT.. the jatco craptastic early ones in nissan were terrible.
The subaru ones are excellent but can be abit annoying if you are used to regular automatic and take a dislike to them.

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post #7 of 13 (permalink) Old 02-23-2017, 12:29 PM
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it depends on the vehicle and other factors. a torque converter is not as efficient as a clutch, so some efficiency is lost and a manual transmission has the advantage. however, a lot of newer cars take advantage of additional gearing (such as the KL) which gives the automatic the advantage over the manual. so the short answer is that there is no short answer.

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post #8 of 13 (permalink) Old 02-23-2017, 01:38 PM
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The CVT in my '17 Subaru Outback performs quite well. I just wish Subaru had not put in fake 'shift' points under moderate acceleration. I would rather it just hold its rpm like most CVT's.

I easily get 6-10 mpg more in my Outback than I do in my wife's TH. Part of it is surely comparing a 2.5 Boxer 4 cylinder to a 3.2 V6, but some of that is also the CVT. The Outback weighs almost as much as the TH, and that 2.5 Boxer has to work fairly hard moving that mass around.

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post #9 of 13 (permalink) Old 02-23-2017, 03:33 PM
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Leaving out CVT (because I think they are crappy)....

For many years it was the manual transmission that took the win on better economy. This was because they used to offer more gearing options, and as mentioned, are direct drive (without slippage) when not shifting.

In the last 10 years autos have not only met, but surpassed the gears, and have become much more efficient at changing gears. It used to be that the torque converter would only lock in 1:1 or OD gears and after some time. Now many autos will lock in every gear when not accelerating. The shifts are now made at speeds that no (normal) human can replicate and are done at the optimum spots while monitoring a whole host of parameters that are oblivious to the average driver.

Having said all that.... I disagree with the fancy computer's decision A LOT and wish our KL had a manual like all of our other Jeeps. We (wife and I) prefer diving manuals, think they are more fun to drive, and are safer as well.

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post #10 of 13 (permalink) Old 02-23-2017, 03:58 PM
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Quote:
Originally Posted by Rand View Post
IN EPA tests automatic will usually win.

In real life it depends on the driver.


.
I would concur...

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