Manual or Automatic transmission..which do you prefer?

[alnorth]

Originally Posted by DJ's left nut

Oh, and you're wrong on the engine breaking thing - you don't use more gas when the RPMs come up during engine breaking. The RPMs are only rising due to the compression in the motor and the motor spinning down. It's not actually using any more fuel; it's the transmission turning the motor in the absence of fuel, rather than the motor turning the transmission. The RPMs come up because there's no place for the energy that the transmission is imparting on the motor to go (i.e. the engine compression) so the RPMs spin up and the compression finally peters the acceleration out. If you were actually feeding the motor fuel to create those RPMs, it wouldn't decelerate.

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.

[Frosty]

Originally Posted by alnorth

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.

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.

[alnorth]

Originally Posted by Frosty

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.

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

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

[Frosty]

Originally Posted by alnorth

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

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

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