Yeah, this whole "coasting down hills in neutral saves gas" thing is apparently a myth. I used to believe it but I've read too many articles by car guys who knew what they were doing saying that the RPM difference in that situation was deceptive. Most of the insane hypermiler techniques that work don't depend on a manual. There might be a small benefit with idling in neutral at a stop.

I still prefer manuals, they are cheaper and more fun to drive, but most of the gas savings come from efficient shifting, not throwing it in neutral.

In a modern car, when you coast in gear (like to slow down or go down a hill), the ecu cuts out the fuel and the engine is driven only by the wheels (down to about 20 mph or so). I agree that it's harmful to slam the tranny down several gears to slow down in the hurry, but done right, it's a big gas savings.

I always try to slow down when I can by just letting off the gas and coasting down in gear. If I need to slow a little quicker, I might drop it a gear. Yeah, it bumps up the rpm's a little because of the lower gearing but you aren't using more gas. Coasting in neutral or with the clutch in saves fuel but is still uses some to maintain the idle plus you don't have the engine braking to maintain speed down a hill (I refuse to risk a speeding ticket in the name of mpg).

Also, you mention people that take forever to get to 50. People that do that are stupid. Any time you accelerate, your gas mileage sucks, so it makes sense to get up to an even speed as quickly as possible (within reason) to minimize the distance accelerating and maximize the distance driving at constant, even speed. About 60 - 70% throttle is the best trade-off.

For myself, I much prefer a manual. If you know what you are doing, it's much easier to manipulate the gas mileage with a manual over an automatic. I also like that you can engine brake down the steep mountain roads I drive sometimes rather than riding the brake all the way down. I also prefer to drive in snow with a manual. If I lived in a city, though, I would probably stick with an auto.


EDIT: DJ's Left Nut is a much faster typist than I.

Electronic fuel injection.

I didn't know that either. I've hill-started my motorcycle a few times by popping the clutch and I know it's an EFI bike, so it must be exclusive to cars.

I have a Scan Gauge II, which is a diagnostic device that plugs into the OBDII port of the car and can give you real time feedback as you drive. One of the things you can get is instantaneous gas mileage.

I have found with several different cars that going from driving in gear to coasting in neutral at speed can make the mileage more than double (it would go up to around 60 - 70 mpg in the car I was testing). If you coast in gear, the mileage readout would say "9999", which basically meant I wasn't using any gas at all.

I've hill started a manual 2001 Prizm (same as a Corolla). It has EFI, so I don't see why that's a problem. I haven't tried it with my manual '09 Forester.

The only thing I want to manually shift is my motorcycle.

I don't care to own a manual transmission car. There is nothing fun about driving in every day traffic with speed regulations.

I don't know Brock well enough to call him a liar. Evidently you don't harbor such consternation.

Thanks for taking the time to make an intelligent reply.

My X doesn't idle at 3k, but it sure as shit will hold at least that when I am coming down the Mtn at a 6-8% grade (I told you I live in CO for a reason).

Are you really going to argue the point that if the same two cars are driving at 3500 rpm and one hits neutral, and the other slowly winds down that there will be no benefit of one engine being at 800 rpm vs 3500-3000-2500- for a period of time? The savings may be fairly minimal and the new trannys may help with this, but no way does that not burn more fuel. It may be semantics at this point, but even that point of releasing the gas vs an almost immediate drop to idle on auto vs manual will create a minimal savings. Remember you are arguing that if I have an s2000 at 9000 rpms and engine brake to a complete stop vs neutral it will be the exact same. Bullshit, you seem to be an intelligent individual, surely you can admit that even though the savings might be minute, a manual is definitely more efficient in this scenario.

I twice said pads were a hundred bucks, a hundred is pretty much standard for any shop to swap the front pads. You're really grasping with that. I have owned several performance vehicles that have been taken to the race track (a real road course, not a parking lot SCCA or circle track). I don't need brake repairs explained to me thank you very much.

Auto with clutchless manual mode. Two of our vehicles have it. Only time I've used the manual shift is for fun. Even in snow the auto works better.

The way I understand it (and I'm not a car guy, this is the dumbed-down explanation I remember), the car always has to remain above a certain RPM to keep the engine going. When you coast downhill in neutral, the car has to burn gas all the way down. When you coast down in gear, as long as the car is above a certain RPM (unclear to me how the RPM happens if not burning fuel), the car doesn't have to use gas.

I use the manual mode on my car almost exclusively. I can get better and quicker acceleration when I manage the gears myself. I only use automatic when my right hand isn't free (like when I'm eating something).

It may be lying to you when coasting downhill in neutral.

http://www.popularmechanics.com/cars...l-fuel-economy

I'm saying that you're looking at 1 of 2 possibilities here.

1) The car isn't going to stay at 3500 rpm - it's going to simply idle down. Unless you're referring to the second it will take for the computer to realize that you're not accelerating (and if you were in overdrive, it shouldn't even take that long), there's no practical difference there. Take your foot off the pedal and your ECU will get to work keeping your mileage up - it's a cheap and easy way for Ford, etc... to improve fuel economy without drastically changing the motor design. Now, the other possibility is what I think you're referring two and thats when you're coasting down the hill (foot not on the gas) and your RPMs have come up to keep you from going 100 mph - in other words, 'involuntary' engine breaking.

2) Again, engine breaking does not have any impact on fuel economy. You may be right, on your steeper grades in Colorado your manual might be pushing 3500 going down the hill. But that's not a true 3500 - it's an idle speed that your transmission is running up to 3500. You're not using any more fuel there than you would if you stepped on the clutch. The fuel isn't what has you at 3500 - the wheels are.

The only difference in MPG would come from the fact that by engine breaking, you're reducing the distance you travel. If it takes you 5 seconds to stop, you will have used the exact same amount of fuel over those 5 seconds as you would have if you'd have just stepped on the clutch - but if you just step on the clutch you'll still be traveling, so your MPG goes up. Presuming, however, that you're stopping for a reason, you're just going to use your brakes to stop at the same point there's no actual travel gain.

I wasn't calling anyone a liar. I was just relating my experience.

FWIW, some hyper-milers do something called "pulse and glide". This is where you speed up to about 10 mph over the speed limit and then throw the car in neutral and coast until your speed drops to about 10 under. Rinse and repeat (it works but is a huge pain in the ass).

In more extreme cases, they will actually turn their cars off during the glide part and bump start it just by dropping the clutch while in gear. This is in modern cars, so it doesn't seem like there is any issue there.

You use no fuel if you stay in gear. The rub, though, is that you can coast farther in neutral than you can in gear so you have to take that into consideration.

That's right. I may have misunderstood your point. I thought you meant coasting in neutral gives you better mileage (over just driving) is a myth.

He's right that it's not exact but point is the large increase, not the exact amount.