hypermiling technique bad for the car?
Many, if not most cars today, are equipped with DFCO (deceleration fuel cutoff) technology. It works whenever you decelerate with you foot completely off the gas and in gear (NOT in neutral). So don't throw it in neutral thinking you're saving gas, you're actually using more than if you just leave it in drive.
Lexus Fanatic
Joined: Dec 2006
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From: californication
good to know. i'm glad i never drive in neutral.
the hassle of shifting constantly.
i do a lot of coasting in gear these days, esp when i see a red light a distance away. keeps my city mpg at 19.
Some people like to speed up to the red light and then brake hard. stupid.
Lead Lap
Joined: Jun 2006
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From: MD
Yeah, but factor in the drag of the transmission while in gear. One will more than likely have to accelerate to make it to the stop light, sign, maintain speed, etc. vs. being in neutral. Obviously, this uses gas.
if the light ahead is red, the engine compression is a good thing to coast and slow to the light anyway. i do this in both my stick miata and my auto explorer.
My 335i's torque converter is very aggressive and puts a lot of drag on the drive train... even in the highest overdrive (6th) gear letting off the gas feels like on a manual transmission car when you downshift a gear or two to slow yourself down... the car just doesn't coast efficiently at all. I understand this is intentional to make the car feel sportier but it really kills me ability to coast to red lights and down hills to get better mileage, so I constantly am putting the car in neutral. Of course it's a little additional wear and tear but I don't think it'd ever end up breaking anything. One think I try to make sure of is that I don't accelerate for a solid second or two after placing the car back in drive, just so the trans get re-situate itself.
This is one of the several reasons I like driving manual transmission vehicles better... in my Audi I was constantly in neutral... basically any time my foot wasn't going to need to touch the gas or brake for a few seconds, I'd just push the clutch in and take it out of gear... that Audi would coast seemingly for a mile or more on flat road if you put it in neutral at 50-60mph and just let it go.
This is one of the several reasons I like driving manual transmission vehicles better... in my Audi I was constantly in neutral... basically any time my foot wasn't going to need to touch the gas or brake for a few seconds, I'd just push the clutch in and take it out of gear... that Audi would coast seemingly for a mile or more on flat road if you put it in neutral at 50-60mph and just let it go.
Lexus Fanatic
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From: Virginia/D.C. suburbs
btw, I've noticed modern high-compression engines seem to have a bit more engine braking too, but maybe some of that effect is due to the modern auto tranny.
Just out of curiosity, I wonder what kind of downhill braking you would get with a typical diesel and its roughly 20:1 compression. I've never tried an automotive diesel down a really long grade.
Lexus Fanatic
Joined: Nov 2008
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From: tech capital
Yes and under that exact same conditions the non-AWD car would get 1 to 2 mpg more. Some of this difference is not just the AWD drag impact but also the shorter final drive ratio most manufacturers spec for AWD versions of cars (to help mask or offset the slower acceleration caused by the additional drag and weight of the AWD system).
Lexus Fanatic
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From: californication
Lead Lap
Joined: Jun 2006
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From: MD
I use my engine to slow me going down mountains, but otherwise I put my car in neutral and use the brakes to slow. Its alot cheaper to replace brakes, which are designed for braking, than to pay for uncessary wear on the engine. I like hybrids with CVTs because they tend to coast like a car would in neutral and wear on the brakes is significantly less given that most braking that is done is with the regenerative brakes and not the hydraulic.
I use my engine to slow me going down mountains, but otherwise I put my car in neutral and use the brakes to slow. Its alot cheaper to replace brakes, which are designed for braking, than to pay for uncessary wear on the engine. I like hybrids with CVTs because they tend to coast like a car would in neutral and wear on the brakes is significantly less given that most braking that is done is with the regenerative brakes and not the hydraulic.