I've been wondering this as i travel 27 miles one way to work going over three mountains. I call them mountains in Pennsylvania but realize I am really a "flatlander" compared to others here. I drive an 4 cylinder Accord with manual transmission. I was taught to always downshift when declining the mountains to "save my brakes/rotors" but was wondering if it is cost effective and beneficial. When I drop the car into 3rd or 2nd gear down the inclines the rpm's will run up to 5000. Granted, I would never let the car run into the redline at 6500 but the car is "screaming" pretty good at 5000 rpm's. Does it use more/less/the same amount of gas to decelerate at 5000 rpm's compared to accelerate at 5000 rpm's? Is there more engine wear with decelerating? Wonder what it does to gas mileage? With the price of gas should I put my car in neutral and use the brakes down the mountain? I know people do this because I follow them and there is no denying the smell of overheated brakes. Replacing brakes/rotors isn't cheap either! I also drop to lower gears with my automatic transmissions going down the mountains. What does everyone else do? What is best practice/cost effective/less wear and tear on vehicle?
More cost effective: Braking or downshifting?
- Thread starter wolfehunter
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Brakes are cheap and easy to replace. Clutches are not.
I have yet to find a car where that does not hold true.
I have yet to find a car where that does not hold true.
+2
On modern manuals, the fuel system stops sending gas into the engine if you take your foot off the throttle while the car is in gear. The MPGs will be infinant. As for clutch wear, how do you downshift? Do you just let your foot off the clutch and let the engine rev up by clutch pressure, or do you rev-match? Proper rev-matching has veryyyy little wear on the clutch. I'd downshift to 3-4th gear, and tap the brakes periodically to prevent them from over heating and excess wear.
In autos i'll drop a gear IF I'm moving slowly, and up hills I keep them in D.
In autos i'll drop a gear IF I'm moving slowly, and up hills I keep them in D.
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I use the brakes. I'd rather put wear and tear on the brake pads instead of the clutch/transmission/engine.
And motor mounts ... they always seem to be a weak spot on FWD manuals.
Use the brakes and let the DFCO save you gas.
Use the brakes and let the DFCO save you gas.
How does downshifting not hurt anything? Even proper rev-matching will make a tiny bit of extra wear. Does anyone put there car in neutral just to coast to a stop sign?
Originally Posted By: 79sunrunner
How does downshifting not hurt anything? Even proper rev-matching will make a tiny bit of extra wear. Does anyone put there car in neutral just to coast to a stop sign?
It puts the same amount of wear as any other shift. It takes very little force to spin the engine up to speed. When I drove stick I always downshifted and never burned up a clutch.
I'd even go so far to say it has way less impact than starting from a stop when you are slipping the clutch.
As far as RPM's, 5k may be a little high but I often let her scream going up and down hills. A properly built engine will have no ill effects.
How does downshifting not hurt anything? Even proper rev-matching will make a tiny bit of extra wear. Does anyone put there car in neutral just to coast to a stop sign?
It puts the same amount of wear as any other shift. It takes very little force to spin the engine up to speed. When I drove stick I always downshifted and never burned up a clutch.
I'd even go so far to say it has way less impact than starting from a stop when you are slipping the clutch.
As far as RPM's, 5k may be a little high but I often let her scream going up and down hills. A properly built engine will have no ill effects.
Originally Posted By: chainblu
If you are on the brakes hard enough to possibly overheat them, I would absolutely use the engine to help slow down. Don't know if I'd use such a low gear to let it rev over 5000 rpm though...
Yeah, just downshift to 4th to get some engine braking and a full fuel cut out. Some cars don't cut fuel fully at 2000-2500rpm, my focus for example. 3rd at 50mph probably doesn't hurt anything but I'd only use 4th if it was me.
If you are on the brakes hard enough to possibly overheat them, I would absolutely use the engine to help slow down. Don't know if I'd use such a low gear to let it rev over 5000 rpm though...
Yeah, just downshift to 4th to get some engine braking and a full fuel cut out. Some cars don't cut fuel fully at 2000-2500rpm, my focus for example. 3rd at 50mph probably doesn't hurt anything but I'd only use 4th if it was me.
Originally Posted By: wolfehunter
When I drop the car into 3rd or 2nd gear down the inclines the rpm's will run up to 5000. Granted, I would never let the car run into the redline at 6500 but the car is "screaming" pretty good at 5000 rpm's. Does it use more/less/the same amount of gas to decelerate at 5000 rpm's compared to accelerate at 5000 rpm's? Is there more engine wear with decelerating? Wonder what it does to gas mileage? With the price of gas should I put my car in neutral and use the brakes down the mountain?
The others that have posted here about Deceleration Fuel Cut Off are right. Coasting down in gear on closed throttle shuts off fuel to the engine, so you are not burning any fuel when you do this. But running closed throttle at 5000 rpm may cause problems with high oil consumption. How is your car doing on oil consumption?
When I drop the car into 3rd or 2nd gear down the inclines the rpm's will run up to 5000. Granted, I would never let the car run into the redline at 6500 but the car is "screaming" pretty good at 5000 rpm's. Does it use more/less/the same amount of gas to decelerate at 5000 rpm's compared to accelerate at 5000 rpm's? Is there more engine wear with decelerating? Wonder what it does to gas mileage? With the price of gas should I put my car in neutral and use the brakes down the mountain?
The others that have posted here about Deceleration Fuel Cut Off are right. Coasting down in gear on closed throttle shuts off fuel to the engine, so you are not burning any fuel when you do this. But running closed throttle at 5000 rpm may cause problems with high oil consumption. How is your car doing on oil consumption?
Brakes are for braking, gears are for accelerating. Now if your going down a prolonged, very steep downgrade and you're worried your brakes may overheat, that's a different story. In normal driving, I'll chug to a stop in whatever gear I'm in and depress the clutch when almost stopped. Keep the car in neutral with the clutch out when waiting for the light - that will save a bunch of wear on clutch fingers and throwout bearings.
I agree with a combination of points here.
There is no fuel being sent to the engine under that condition so the MPG is not an issue.
There should be minimal wear on the clutch, especially if you're rev-matching.
There should be minimal wear on the engine as it would be running at _,___K RPM anyway and it's designed to go hundreds of thousands of miles, that said, I probably wouldn't have it spinning at 5K.
There is no fuel being sent to the engine under that condition so the MPG is not an issue.
There should be minimal wear on the clutch, especially if you're rev-matching.
There should be minimal wear on the engine as it would be running at _,___K RPM anyway and it's designed to go hundreds of thousands of miles, that said, I probably wouldn't have it spinning at 5K.
Originally Posted By: 79sunrunner
On modern manuals, the fuel system stops sending gas into the engine if you take your foot off the throttle while the car is in gear. The MPGs will be infinant. As for clutch wear, how do you downshift? Do you just let your foot off the clutch and let the engine rev up by clutch pressure, or do you rev-match? Proper rev-matching has veryyyy little wear on the clutch. I'd downshift to 3-4th gear, and tap the brakes periodically to prevent them from over heating and excess wear.
In autos i'll drop a gear IF I'm moving slowly, and up hills I keep them in D.
This works, and I try to do it as often as I can to incrrease mpg. Additionally, I believe there's likely some benefit from the reverse sliding activity that happens when downshifting, as opposed to normal upshifting. I think it might actually improve the clutch/pressure plate interface.
I've probably gone a million miles in manual transmission vehicles and haven't worn one out yet. I broke a few on a Datsun I had but, that's a different story.
On modern manuals, the fuel system stops sending gas into the engine if you take your foot off the throttle while the car is in gear. The MPGs will be infinant. As for clutch wear, how do you downshift? Do you just let your foot off the clutch and let the engine rev up by clutch pressure, or do you rev-match? Proper rev-matching has veryyyy little wear on the clutch. I'd downshift to 3-4th gear, and tap the brakes periodically to prevent them from over heating and excess wear.
In autos i'll drop a gear IF I'm moving slowly, and up hills I keep them in D.
This works, and I try to do it as often as I can to incrrease mpg. Additionally, I believe there's likely some benefit from the reverse sliding activity that happens when downshifting, as opposed to normal upshifting. I think it might actually improve the clutch/pressure plate interface.
I've probably gone a million miles in manual transmission vehicles and haven't worn one out yet. I broke a few on a Datsun I had but, that's a different story.
No contest- use the brakes sanely. Compared to clutches, transmissions, u-joints/cv joints, etc, brakes are dirt cheap to repair.
Great information!! Thanks a lot. I have no oil consumption. What exactly is rev-matching? I have driven sticks for 30 years and never heard that term so therefore I don't think I am doing that with my car. I also have only replaced one clutch and that was in a an old chevelle big block and for obvious reasons!! I usually only run the rpm's up to 5K when I downshift from 3rd to 2nd at the hairpin turns on the mountain. And I "cushion" or tap the brakes rather than ride on them to help slow the car. But it sounds like I should be rev-matching? Could someone explain?
Originally Posted By: bigt61
Brakes are for braking, gears are for accelerating. Now if your going down a prolonged, very steep downgrade and you're worried your brakes may overheat, that's a different story. In normal driving, I'll chug to a stop in whatever gear I'm in and depress the clutch when almost stopped. Keep the car in neutral with the clutch out when waiting for the light - that will save a bunch of wear on clutch fingers and throwout bearings.
++++1
Brakes are for braking, gears are for accelerating. Now if your going down a prolonged, very steep downgrade and you're worried your brakes may overheat, that's a different story. In normal driving, I'll chug to a stop in whatever gear I'm in and depress the clutch when almost stopped. Keep the car in neutral with the clutch out when waiting for the light - that will save a bunch of wear on clutch fingers and throwout bearings.
++++1
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