How should I drive my uphill commute?

October 26, 2005 12:05 PM

Driving tips for an uphill commute?

My commute includes 10 continuous miles of 4-6% grade. It's uphill on the way to work, downhill on the way home. I drive a 2004 Subaru w/ manual transmission. What tips do you have to help me increase my gas mileage and prevent wear on my car?

posted by jgee to travel & transportation (24 comments total)

The most important thing you'll be able to do to prevent wear on your car is to downshift on the way home to take advantage of engine braking and minimize the use of your brakes.
posted by kindall at 12:11 PM on October 26, 2005

Don't shift to slow down. Brake pads are far cheaper than a new clutch.
posted by blue_beetle at 12:25 PM on October 26, 2005

kindall: that action would cause jgee to use *more* gas, not less.
posted by lester at 12:26 PM on October 26, 2005

blue_beetle, kindall's suggestion won't wear the clutch at all. he's suggesting keeping it in a lower gear to allow engine braking.
posted by lbergstr at 12:30 PM on October 26, 2005

On the way to work, stay in a higher gear. lower rpms usually mean less gas consumption.

On the way home, put it in neutral and coast down the hill.

If the grade is too steep coming down, there is nothing wrong with engine braking. Just be sure to rev-match if you're downshifting. It's a good skill to learn, and once mastered, no clutch abuse will be necessary!
posted by freq at 12:34 PM on October 26, 2005

Usually, when one shifts to a lower gear for engine braking down a hill, the RPM will be high enough to enable fuel cut-off, so you won't be using any gas at all ...
posted by rfs at 12:34 PM on October 26, 2005

You also need to keep your foot off the accelerator pedal for fuel cut-off.
posted by rfs at 12:39 PM on October 26, 2005

Recently on Car Talk the guys talked about driving a car with an instantaneous gas consumption indicator and one of the things they noticed was that the difference in gas consumption between accelerating slowly uphill and accelerating more aggressively was huge. If they and the gauge are to be believed the most important thing you can do is drive easily and accelerate in a higher gear, providing you are not lugging the engine.
posted by phearlez at 12:40 PM on October 26, 2005

The Car Talk guys have also recommended not using engine braking too much because brake pad are cheaper than drivetrain components.
posted by probablysteve at 1:17 PM on October 26, 2005

Other people must have amazingly fragile clutches. I downshift for braking all the time, and am still on an original clutch with 140,000 miles, and the last stickshift car had something similar before its clutch finally went (and it got driven *hard*).

Even if clutches wore as fast as people seem to think they do, replacing a clutch is a whole damn lot cheaper than overheating your brakes on a long downhill, losing function, and dying.
posted by ROU_Xenophobe at 1:41 PM on October 26, 2005

If your Subaru is under warranty, the clutch is a covered part. i.e. If you wear out your clutch, they'll replace it for 'free' if you're still under the manufacturer's warranty.

At least, it was covered a few years ago. YMMV, no pun intended.
posted by Wild_Eep at 2:00 PM on October 26, 2005

Just be happy you're doing this in modern times. Back in my grandpa's day, such a commute was uphill BOTH ways.
posted by luriete at 2:09 PM on October 26, 2005

What rfs said about the fuel cut-off is correct. Engine braking doesn't put undue strain on the drivetrain either. (you're putting much more power throught the drivetrain when you accelerate) Brake fade would probably not be a problem and replacing brakes is indeed cheap, but you will be saving fuel if you engine brake. On neutral, you will be using more fuel and you would have to use your brakes. New cars have indeed been designed with engine braking in mind.
Uphill, there are no special tricks apart from the usual. The most important thing for fuel economy is to try to maintain a steady speed instead of slowing down and accelerating again.
posted by lazy-ville at 2:26 PM on October 26, 2005

Engine braking doesn't put undue strain on the drivetrain either.

I don't remember it being drivtetrain components (I actually thought they said transmission, though it was a while ago) but I also have heard the cartalk guys saying that foot braking is better than engine breaking, for reasons of brake pads being cheaper than X (where X is some piece of a car). And they do often seem to know what they are talking about...
posted by advil at 3:11 PM on October 26, 2005

On neutral, you will be using more fuel...

Wow, what kind of car do you drive? I'd love a car that giving the engine more gas meant using less gas than not giving it any!

On a serious note, on a long commute downhill, brake fade might well be a problem (it certainly is when you're driving around in the mountains). If you do go the neutral + brake route, make sure you slow down in bursts, and don't ride the brakes the whole way down.
posted by devilsbrigade at 3:24 PM on October 26, 2005

Wow, what kind of car do you drive? I'd love a car that giving the engine more gas meant using less gas than not giving it any!

Why would you give the engine gas when engine braking? On neutral, the engine is using fuel to keep itself running. When engine braking, the engine is moved by the kinetif energy of the car and therefore does not need any fuel. The ECU knows this and cuts off fuel supply to the engine.
posted by lazy-ville at 3:45 PM on October 26, 2005

Thanks for the suggestions. I'm marking freq and lazy-ville for best answers. Thanks to freq for introducing me to rev-matching, and thanks to lazy-ville for the quality of the answer and subsequent follow-ups.
posted by jgee at 3:54 PM on October 26, 2005

The Car Talk guys have also recommended not using engine braking too much because brake pad are cheaper than drivetrain components.
posted by probablysteve at 1:17 PM PST on October 26 [!]


I heard that show too. For a continuous long downhill you kind of have to use the engine because your brakes just can't take the heat (literally). I think they were talking more about shorter downgrades, seconds of travel not tens of minutes.

To save gas, remember what they taught in the seventies, just pretend you have an egg between your foot and the gas pedal. Try not to break it.
posted by caddis at 7:13 PM on October 26, 2005

Speaking as an engineer for an auto company, on every test trip I've been on it's expected that people will use engine braking in the mountains to save their brakes.
posted by rfs at 7:44 PM on October 26, 2005

You guys that are saying "brake pads are cheap, use them" are completely and totally off your rockers. DO NOT DO THIS ON LONG HILLS.

Everyone that's quoting car talk must not have been listening either. They don't recommend engine braking for day-to-day normal city driving but they most certainly DO recommend it for long, continuous grades as the poster is asking about.

The reason that you should NEVER EVER use your brakes on long continuous hills is that they will overheat and glaze, and then you will have NO BRAKES AT ALL when you get to the bottom of the hill.

On top of that, engine braking uses zero fuel, and it does NOT damage the drivetrain if done properly.
posted by Rhomboid at 6:02 AM on October 27, 2005

And if you don't believe me about brakes overheating, why the heck do you think you see so many "emergency truck pull out" ramps on mountainous roads? And those guys are trained professionals. It can happen to anyone, and I have to say it is damn scary when you try to stop and the brake pedal just does NOTHING.
posted by Rhomboid at 6:06 AM on October 27, 2005

Yeah, on a drive like this it's not even an option to use your brakes like that. I should have clarified my question and said that I was looking for tips outside of the commonsense stuff.
posted by jgee at 4:49 PM on October 27, 2005

As Rhomboid says, I and the other car-talk quoters were apparently wrong (3 links) unless they've changed their mind since 1997 (though I was really sure I'd heard this in the last few years).

why the heck do you think you see so many "emergency truck pull out" ramps on mountainous roads?

There may be many reasons, but one is probably simply that trucks can weight 40000-80000 pounds (based on a cursory web search). A car or minivan, on the other hand, has a curb weight of around 2000 (toyota corolla)-5000 (ford truck) pounds.
posted by advil at 9:27 PM on October 27, 2005

Of course, trucks have a lot more weight to slow down. However, they have much larger brake rotors/pads on the wheels, plus many more wheels to distribute the braking, plus they have engine braking from the jake brake device. My point was that those guys know damn well if they ride the brake pedal they will lose their brakes in no time because of the enormouse amount of heat, so they all know how to engine brake. And yet even knowing that and having training with engine braking, they still occasionally mess up and ride the brakes too much during a descent and end up cooking them, and have to use the emergency ramp. If it can happen to them it can happen to you.
posted by Rhomboid at 11:43 PM on October 28, 2005