Does downshifting decrease gas mileage?

[GottaHaveLS1]

I know it raises the RPM's but the throttle isn't opening more and the injectors aren't spraying gas right? I also heard that leaving the car in neutral (m6) and coasting a lot will throw ur trans out of sync...

What do you guys think?

[GottaHaveLS1]

looks like it's too dumb of a question to ask

[shady milkman]

um it really isn't noticeable from what i am told. i have never heard about nu throwing the tranny out of sync tho..

[camarojunky74]

okay after breaking a few manuals you kinda understang how they work plus i took numerous classes on manual transmissions, doing this neutral thing is not going to take your trans outta sync, what you have heard my have been reffering to as the synronizers or synchros, because say your in 6 gear cruisin and you crest a hill, if you were just to push in the cluch and take it outta gear, while holding the clutch the whole time you are coasting that neccesarily wouldnt be putting any unnecessary stress on the synchros and the shift forks, but if you release the clutch and coast than put the clutch back in and put it into gear you are putting stress on the synchos and forks much more than just up shifting or downshifting because you are asking the synchos to try to slow down that gear much more than i guess its desighned to do.

does that big as sentence lol make any sense?

[INMY01TA]

If your rpms are high your injectors ARE spraying. No that wont hurt your trans.

[silverz28camaro]

think about it.... your injectors are spraying all the time. Even at the same throttle position you motor will burn more fuel at 2500 rpm rather at 2000rpm simple because you are filling the cylinders with a fuel ratio more often.

[jrc1122]

think about it.... your injectors are spraying all the time. Even at the same throttle position you motor will burn more fuel at 2500 rpm rather at 2000rpm simple because you are filling the cylinders with a fuel ratio more often.


with my limited mechanical knowledge,, I wasn't going to add my 2 cents. but this sounds dead, on.

Your pistons are moving up and down faster, combusting more gas, thus using more gas, effecting gas mileage.

Other wise people would never shift into 6th to "save gas".

[GottaHaveLS1]

I agree-Should have bought a SMART car and have a sail manufactured for the roof:tap:

thanks for your wonderful input

[Mr. Luos]

You use MUCH less fuel under decel then holding speed.

Yes...your injectors are spraying...but barely. They don't need to.
Injectors are 'basicly' controlled by the throttle sensor. More throttle = more fuel. Less throttle = less fuel.
Obviously there are many other things the computer looks at to determine how much fuel to spray.

Don't need fuel to slow a motor down...just to get it spinning.

[AKIRA]

Im not sure I agree with that statement. It wouldnt work both ways..

[LS2Tuner]

There are many variables on your downshifting ? On the coasting I would tell whoever told you that to set the pipe down and walk away.
By NO means is coasting in neutral for extended periods going to throw your trans out of sync.

[mbrownin]

Im not sure I agree with that statement. It wouldnt work both ways..

Which statement are you referring to?


You use MUCH less fuel under decel then holding speed.

Yes...your injectors are spraying...but barely. They don't need to.
Injectors are 'basicly' controlled by the throttle sensor. More throttle = more fuel. Less throttle = less fuel.
Obviously there are many other things the computer looks at to determine how much fuel to spray.

Don't need fuel to slow a motor down...just to get it spinning.

This one? Sounds right to me. When throttle is closed, very little air through the intake, so very little fuel since the computer tries to maintain a constant AFR, and vice versa.