Manual vs automatic What is desirable for MPG?
 

Hello all,

I thought for sure I'd find a pretty good post on manual vs automatic tranies somewhere here! If there's something I missed, please let me know.

OK just to let you know, I'm a manual fan here. I am persuaded if someone can convince me that my next car should be an automatic. I tend to go for smaller and less powerful vehicles, I don't need the biggest or greatest. I always go for used vehicles too. The big thing here is that we have a good idea the trans that most desirable for MPG.

You're asking for someone to persuade you? For some reason.

I used to be a manual fan like you. I might still swap the 5-speed transaxle into my Superbeetle at some point.

But IMHO the best transmission in this day and age is the twin single-speed electric drive with differential and torque vectoring in software. Not so big on over-the-air updates.

trannies
 

In the past, Ricardo Engineering reported the highest efficiencies for CVT.
A 12-speed would have the equivalent efficiency.
We're up to 10-speeds presently.
BEVs with one-speed planetary gearsets have THE highest efficiencies in mpg-e.
Carmakers which claimed more efficiency for a 2-speed BEV transmission, and who produce a 2-speed BEV, have the lowest observed efficiencies of BEVs, although, perhaps not soley on account of gearing.
What's desirable is zero 'transient' loading of internal combustion engines, on account of a drift in the BSFC of the engine.
BEV's have, for all intents and purposes, a constant BSFC which is about 350% lower than an ICE.
Thermodynamically, ICE powerplants are presently the least efficient, and as motorists learn to count, are on their way out, by default.

About 3% of new vehicles sold are all electric and there's lithium battery shortages.
Internal combustion engines aren't going anywhere.
An argument can be made that fully electric are worse for the environment.
If each electric car saves about 400 gallons of gas. Sounds good right but the impact is tiny.
Let's say instead of one EV we make 6 plug in hybrids using 1 electric car worth of batteries. Now you're saving 200 to 380 gallons of gasoline times 6.
Or say instead of 5 plugins you make 30 prius like hybrids with one electric cars worth of battery, each hybrid saves up to 100 gallons of gasoline per year, times 30.
So we are far better off making prius like hybrids and keeping internal combustion engines.

Obviously hybrids are going to have automatic transmissions.

While the EPA rates many automatics higher than manuals today I think that's a product of the test method. You can drive a manual more efficiently than an automatic but the EPA test cycle doesn't allow a low rpm shift on the manual while they do allow low rpm shifts on the automatic. Basically the automatic gets to do what the car knows is best, while the manual has to be shifted by some ancient book the epa put together. That's why you see lots of people here beating the EPA estimates by a bigger percentage with manuals compared to automatics.

Obviously the exception to that rule would be the gas range extender:

Generally speaking, a manual transmission will be more efficient. That's assuming you know how to drive it efficiently.

However, the automatic transmission has undergone a paradigm shift. Many of the automatic transmissions nowadays are automated manual gearboxes, or CVTs. And the fuel economy can rival or even beat a manual transmission, depending on how you drive it.

So the answer to your question would depend on which particular transmissions you're comparing, and your driving habits.

Or even no transmission at all, relying on one of the electric motors to provide reversing, while also simulating the effect of a CVT.

I like manuals because you can quickly and safely put it in neutral in well under a second at any time by just pushing in the clutch or quickly back into gear by releasing it. If you want to maximize coasting with minimum amount of drivetrain drag, this is it.

Maybe a brand new vehicle can be this quick shifting into neutral with paddle shifters, or CVT, I don't know I have never driven one.

Automatics can't scan the road ahead and assess whether RPMs will be going up or down.