Manual or Automatic transmission..which do you prefer?

[alnorth]

Originally Posted by Frosty

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).

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.

[Frosty]

Originally Posted by DJ's left nut

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

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.

Originally Posted by COchief

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.

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.

Originally Posted by alnorth

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.

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.

[alnorth]

Originally Posted by Frosty

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.

I'm saying that the idea that coasting in neutral saves gas over coasting in gear, is a myth. You should coast in gear.

[Frosty]

Originally Posted by alnorth

I'm saying that the idea that coasting in neutral saves gas over coasting in gear, is a myth. You should coast in gear.

Agreed to a point. As mentioned, you can coast much farther in neutral than you can in gear so you have to consider that. I have some hills that I can't maintain speed in gear but can in neutral so I save gas over slowing down in gear and then having to accelerate back up to speed or just driving normally. You have to figure out when each method is best.