My friend and I were arguing yesterday about downshifting as you come to a stop light or turn. I don't think it's necessary, and he thinks you should always do it. If i see a stop light, I put it in neutral and coast to a stop applying the brake. He says that downshifting will help you slow down. But if you're downshifting properly (rev-matching at each shift) you wouldn't really be slowing down, the rpm would just be higher in a lower gear. Could someone please settle this once and for all?

 

Your friend is right. Downshifting will slow you down with the resistance of the motor and the high rpms as they slowly drop. Is it gonna stop your car completely? No, but it will save you a lot on brakes instead of coasting in neutral. Also its not very wise to be in coasting out of gear in the first place just in case of an emergncy situation you rather be in gear making power.

 

It can also be a safety issue to not leave it in gear in the situation that the motor should stall If you were coasting up to a red light down a road in neutral, and your car stalls... you would instantly lose your power steering and this could lead to a crash.

If you had the car in gear, the engine cannot stop spinning... even if you cut the ignition... the motor will still be turning, which will keep the power steering pump turning and allow you to maintain control of the car.

You don't need to downshift through all the gears on the way to your stop, but it's a good idea to at least leave the car in gear until it the RPM's start to get to the point where they're a few hundred RPM's above idling. This will also save you on gas, since it's more efficient to coast to a stop with the car in gear than in neutral(your car uses no gas whatsoever while coasting in gear with your foot off the skinny pedal, whereas you will use a little bit of gas to keep the car idling if you coast with it in neutral).

Pros of coasting in gear(I'm not talking about compression braking... just coasting in gear to a stop):
-Better gas milleage
-No risk of crashing should the car stall
-Safer, in the event that you should suddenly need to hit the gas to avoid a collision
-Less braking is required to stop the car because the engine acts like a weak brake and this can lead to longer brake life without any additional clutch wear

 

no aditional clutch wear but your using your transmission and its parts to slow the car down. id rather pay 100 for pads...

 

I put the car to neutral to save gas. You don't save that much each light, but it adds up.

I don't downshift to slow down. I downshift to get into the proper gear to have enough revs to properly exit the turn.

How do you figure this? With each rpm, you're burning more fuel. Even hypermilers use neutral to save fuel.

 

Thanks guys, thats not the favorable answer - now I have lost the argument! But good information nonetheless. I kinda feel like there's not enough time to be downshifting when you're coming to a stop, especially if you're doing like 50 mph on a busy road. I guess it just takes some practice??

 

I thought it was just explained that you use MORE gas coasting in neutral versus leaving it in gear and letting the RPM drop.

 

that's what i do

 

just leave it in gear until the RPMs get to about 1000, then clutch in and go to neutral

 

That's the key, isn't it? I've noticed since I started driving a stick that I keep a greater following distance specifically so that I can down shift before a traffic light or a stop sign. I don't think it's extremely practical on a highway and it's not often that I down shift on a highway - usually not enough time.

 

The G is hard to do it with but you just need to practice.

 

i do the same also.. i thought i was jus being cheap

 

I believe you're talking about this post...

Your car burns fuel as it revs, even if it's dropping in revs. Drop into neutral and your motor is idling, burning almost nothing. If leaving your car in gear saves fuel, then technically, rev matching wouldn't waste so much more fuel over normal driving. We can easily test this on a dyno. I already know the results...

 

Okay so it sounds like in order to save gas, drop in neutral and use the pedal brake for coming to lights. But it may be safer to stay in gear in case of an emergency (although I can not think of one situation where being in gear would be beneficial).

Also, while approaching turns and downshifting, is it bad for the transmission to go from like 5th to 2nd gear as long as you're rev-matching? My friend says you should downshift 5th to 4th to 3rd to 2nd to save the synchros or some cr@p like that. Opinions?

 

for me it comes down to fun.... i usually downshift to slow down cause it's fun, and then im in a lower gear so when i exit the turn or the light turns green i can jump on the gas and have instant acceleration cause im already in the gear i wanna be in