Stretching the Gallon on the Road

[Hampton]

I've been really working hard at getting as good of gas mileage as possible lately. Without making any mods to my truck, I've been changing my driving habits to increase my gas mileage significantly. If I didn't work at it at all, I'd get about 15 mpg. For the last few years, I've been getting around 16. Lately, it's been closer to 18. I'm trying to get 18.5 this week.

I've been filling up the tank every time which doesn't help due to weight. I get about 1/2 - 1 mpg better at the bottom of the tank than the top. The key to the extended mileage is coasting up to stop signs and red lights in place of cruising up close and then using the brakes. Reasonable acceleration also helps. I don't jam up traffic in attempt to stretch the numbers, though.

I have actually put the truck in neutral and shut the engine off when approaching an intersection with notoriously long waits. I coast up and stop, then start the truck just before it's time to proceed. This can be dangerous (blah blah blah). This week, I've started turning the A/C off when I accelerate. I notice that the A/C can cost up to 2 MPG in the city.

My driving takes me through some 25 mph neighborhoods, some 35 mph connecting streets, and lots of 45 mph zones. I drive 15 miles each way to/from work. There are 12 traffic lights or so. It's like city driving, but not the worst case type of city driving. My mileage actually decreases on the highway due to increased wind resistance.

The biggest drag on fuel economy is using the brakes - If you use your on-board computer, you can see that mileage goes waaayyy down when accelerating, even when accelerating mildly (2 mpg to start, then 3, 4, 5, 6...) Cruising, I get about 22 - 24 mpg at speeds between 25 and about 52. It goes down as you speed up beyond that. Coasting, mileage goes up to the 80's from high speeds or 40's from moderate speeds. If you accelerate from a stop and then brake to the next stop, you spent time at 2 mpg but very little at 60 or 80 mpg. It's almost as efficient to accelerate and then coast as it is to just cruise. If you shut the engine down, it may actually be better than straight cruising, but the computer doesn't register that. It's not uncommon for me to coast 1/4 mile with the engine off when the light ahead is red - the trip computer doesn't register any additional mileage, even with the key back on to "run." That being said, actual gas mileage goes up, the computer just can't track it.

When I put gas in the truck, I keep track of how much fuel it took compared to how much the computer indicates. The computer is always off by about a gallon, or 5%. I take that into account.

I get over 450 miles per tank. With zero traffic, it costs me an extra 2 minutes to get to work (24 vs 22). With traffic, it's much harder to get great mileage, but you can still do it and then it doesn't cost any time. The best thing to do is leave enough room behind the car ahead so that you don't have to brake much when he slows to turn off.

If I'm turning ahead, I'll try to slow so that I only have to apply the brakes to lose the last 10 mph or so. If I'm going to have to stop (stop sign...), I'll coast from 45 (or 48, 50) to at least 35 or below. If the speed limit is 35, I'll try to coast to 25 before I need to brake normally. Coasting below 25 mph in gear will take you for miles. I don't do that to the folks behind me.

Timing traffic lights is probably the best aid to great gas mileage. I know the habits of each light. I check for left-turn arrows, and oncoming traffic waiting to turn left. The light at the Wal-Mart stops the 45 mph thoroghfare traffic immediately when someone on the side street is going to/from the F'n Wal Mart - pisses me off. If you can keep the 2 1/2 ton truck moving along, the gas mileage goes way up. When accelerating from a dead stop, I try to let the engine start the truck moving in idle prior to applying the gas - this helps lessen the gas consumed at stops.

My truck's curb weight is a little over 5,000 lbs. and I get around 18 mpg and have 335 hp and/or almost 400 ft/lbs of torque when I need it - altogether, not too bad. How about you guys?

 

[DCarl320]

I always enjoy when I can get 400 miles out of a tank, 450 is unreal!! Saw a news report not too long ago about a guy who employs alot of those same techniques and he also gets remarkable results. But unlike you (I'm sure) he employs rolling stops. Most places will get you a ticket for that.

When I was driving charter busses we were also taught many of those techniques not only for fuel conservation but for safety purposes, It was called the Smith System http://www.smith-system.com/ check it out, It has already saved thousands of lives, and thousands of miles. :grin:

Get yourself a tire gauge and this should put you in the running for Obamas Energy Secretary. :lol:

 

[Hampton]

I'm only buying gas twice a month ($100 each time). It's pretty cool. The Smith system seems pretty good. Looking way down the road and thinking about a strategy for not having to stop takes thought. When I'm on the phone, I find myself using the brakes a lot more due to less active planning.

 

[VTSeaRay]

I like the work from home system... I use it 4 out of 5 days or so a week. Unfortunately, not everyone can do that. It gives me back an hr in commute time each day, not to mention no fuel costs and no mileage on my vehicles. And, during my lunches and breaks, I can do stuff around the house (laundry, cleaning, mowing, etc.). When I do drive, I try to use some of the "hypermiling" measures you listed. I try to stay off my brakes as much as I can. My real gas killer, is I'm sure, taking off... For some reason, I like to crank on it on takeoffs.

-VtSeaRay

 

[KIMO]

Only make right turns.

A couple of years ago UPS announced it's drivers would no longer make left turns. Their study showed the time waiting/idling at left turns burned a lot of fuel and that their GPS/route manager system would plan out delivery routes right turn only.

Here is one article: http://multichannelmerchant.com/opsandfulfillment/advisor/fuel_conserve/
but there are plenty of others if you Google ups right turns.

 

[fwebster]

Driving habits are certainly important to achieving fuel economy. I use John's methods in long distance travel to the coast and am getting 27 mpg in a V-8 sedan with defensive and conservative driving habits.......but I don't turn the key off and coast!

Some time ago, when fuel was about $2.00/gal, I decided that my usual mode of transportation was wasteful. Me and one dog usually were the only load in a 3/4 ton pick up truck and I looked for an alternative. I decided that a small diesel car would save more fuel than any other single thing I could do since diesel converts to almost 18% more energy than gasoline. Me and the dog ride around in a VW TDI at 45 mpg now.....and driving habits don't seem to make much difference.

 

[Hampton]

Frank,

I have heard that your particular vehicle gives the best bang for the buck on the road.

 

[Four Suns]

This is a joke... right?

John: Go buy a moped and stay off the road. Then go buy a sailboat and get rid of the gas boat as it burns more fuel in one outing than you'll save all year being a pain in the ass around town. Turning your car off and coasting is dangerous (power brakes and steering?) not to mention annoying to the drivers around you.

I mean... COME ON!!! Sounds like Al Gore giving a talk on being "green" then getting in his private jet and flying back to his old 15,000 sq ft. house.

 

[Four Suns]

Oh yeah... what airline you fly for? I don't want to be at 30,000 feet and have you shut the engines off and glide to save fuel...

 

[Four Suns]

WAIT! I got a better idea...

When you take your boat out, make sure you check the tides and just turn the engine off in the channel and drift to your next destination... Mrs. Robinson will be right there with you.

 

[JVM225]

I save fuel by not going to work every day (I'm retired). I do some side work to keep busy, but lots of it can be done from home. When I do have to go out on something I charge my clients for mileage.
I've really tried to consolidate trips to conserve fuel these past few months. I was surprised at how much I saved by planning out errands.
The current price of gas has also made me re-think the fleet.
The boat stays because that is recreational and I can decide how much I want to run it. In fact, I've put as many hours on it this year as I did last year and it has been worth every penny. I can't put a price on the memories it is building for my kids. I might even take advantage of the lower prices and upgrade a bit.
The other toys (07 Corvette convertible and 68 GTO) stay because they are recreational, I can decide how much I want to drive them, and can't put a price on the enjoyment I get from them. Besides, the Corvette gets incredibly good gas mileage.
The two regular daily drivers are going to change this winter. The mini-van is a goner; as much as I love the comfort and convenience, it just isn't worth all the gas it burns for the few times I need the extra capacity.
My wife's Jeep is sticking around but will be demoted to extra vehicle status to be used when I need to fold down the rear seat and carry big things around (mostly back and forth to the boat), and on snowy days. It gets lousy gas mileage too, but owes us nothing at this point; plus it's fun to drive.
We will be leasing two four cylinder four door cars for daily driver useage around town. We are both due for new cars anyway, and I figure that as long as we're in the market we might as well look for cars that get good gas mileage.
$4.00 a gallon gas won't break me, but enough is enough. I don't mind spending it for recreational things, but why waste money just for basic transportation. A nice little Accord or Camry can be very comfortable too. A few years back I leased a four door Accord and we made two round trips from NY to Florida in the thing. It was actually pretty comfortable.

 

[Hampton]

JVM - Excellent plan. I agree with your thoughts about saving gas while I can, and then choosing to use it when I want.

 

[Hampton]

Oh yeah... what airline you fly for? I don't want to be at 30,000 feet and have you shut the engines off and glide to save fuel...

While we do not shut engines down on purpose, the 757 was having problems in its infancy with engines quitting when the throttles were advanced after idling for extended periods during decents. If a pilot gives a dang, learns his aircraft well, and takes environmental conditions into account, he can generally save about 3,000 lbs of fuel on a standard cross-country flight.

Though it's been a couple of years, I'll try to regergitate a couple of numbers. The standard ratio to determine decent point used to be 3:1 for planning purposes. That means that if you are cruising at 41,000 feet, you would need to start your decent 123 NM out from your destination. Most guys go with that, and add 10NM to allow for a nice, easy transition from cruise to decent.

If you really want to save gas (which is a challenge which I enjoy), then you take winds and other factors into consideration. If you consider the winds at various altitudes, then you can calculate an adjustment to your decent point. Also, you have to consider approach control altitude restrictions along your decent - these matter more than your runway altitude as they will be the next actual limitation. You have to consider whether your flight path is aligned with the landing runway, 90 degrees out, or 180 out. The key is to not just use the distance to your runway, but the actual flight distance (winds alter this distance).

Then, you need to consider the time of day and air traffic congestion. By using TCAS (part of transponder that shows most air traffic), you can see the line of aircraft approaching the field, and from that, you can determine how extensive of vectors (extended flight path) you can expect to receive to adjust your flight distance. Once you have taken all of those into consideration, you then have to decide the actual glide path that your aircraft will have on that day. If you're really light weight, your glide ratio will be greater. If there are airspeed restrictions, it can be affected either way, but in most cases, restrictions cost you fuel unless you can plan your decent to hit those restrictions with little affect.

Aircraft today have computers on board to take a lot of the thought out, but they are wrong. Example - in the case of the 757's engines flaming out after extended use at idle, they bumped up the idle fuel flow, so, the 757 actually takes quite a bit more distance to descend (it's like coasting in your car below 25 mph - lasts forever). On account of this, it is actually more efficient to stay high longer, and use speedbrakes at the last part of the decent (imagine your car being set at a really high idle - you wouldn't want to coast for 3 1/2 miles at 22mph to a stop sign - you'd use your brakes at the end).

As you decend, you have to continually update your plan. They may be crossing traffic that will affect your decent profile - monitor the radios and TCAS and plan for such an event. Don't let a complacent air traffic controller stop your decent - pimp them for continuously lower altitudes. If you find you're decending too early, stop NOW (slow decent angle) to take advantage of the thin air up high.

Once you are in the low altitude regime, you now make adjustments to your decent rate by milking the flaps down at an appropriate rate based on your airspeed, decent rate, position in traffic... Airlines flaps generally work as follows: The first increment extends the leading edge slats. Subsequent actuations may add more LES, and add some trailing edge flaps. Trailing edge flaps generally extend aft (bigger wing) before they begin to droop down. As all of these devices come out, the initial effect is to make the wing more efficient at slower speeds which will extend your glide path (more lift). As you put out more devices, they then begin to decrease the efficiency and increase the decent rate (more drag). This is required because aircraft are so aerodynamically clean these days that without throwing out the anchors, you would have to decend at 1 degree all the way to landing in order to stay slow enough to land. You would be hitting trees, buildings and dirt for miles before the runway.

Bottom line: The goal is to retard the throttles to idle at 41,000 and leave them there for the next 120 NM, slow the plane, hit all of the restrictions, milk the flaps down, start down on your final approach course and glide path, lower the landing gear, throw out the last flaps, and then increase power above idle to stabilize on speed at 1000 feet above the ground in the weather (3 mile final) or 500 feet above the ground on a clear day (1 1/2 miles), just prior to landing.

Other considerations:
Icing - icing requires higher power settings which will extend your glide.
Configuring early - Unskilled, unconfident, and lazy pilots don't do math, get down early, put the gear and flaps down early, and cost literally thousands of pounds of gas per leg.
Many, many more.

Too high? Use speedbrakes. Too low? Correct early and re-acquire your desired descent path. Controller messes up (it happens - a lot)? Make him fix it. They frequently ask "Well, you have speed brakes don't you?" I love the reply "Speed brakes are for my mistakes, not yours."

Flying fighters here at Tyndall, I'm always working the gas - stretching the legs of the aircraft while still making tactically sound decisions. It's really easy to piss away all of your gas for very little gain (cruising around at transonic speeds for no reason, when supersonic would be quicker and more fuel efficient). It's not at all uncommon for me to take off in a flight of 4, employ with the other 3 for an hour and a half, return to base with the others, and then fly and extra 5 or 10 minutes in the pattern or along the coast due to having saved an extra 1000 pounds of gas.

As you may have noticed, it's an interest of mine, and I'm always working the numbers.

 

[Hampton]

being a pain in the ass around town.

Turning your car off and coasting is dangerous (power brakes and steering?) not to mention annoying to the drivers around you.

Quotes from my post:

"I don't jam up traffic in attempt to stretch the numbers, though."
"Coasting below 25 mph in gear will take you for miles. I don't do that to the folks behind me."

"This can be dangerous (blah blah blah)."

Gee, I never thought about the brakes and power steering (read in deeply sarcastic tone). If they're annoyed because my engine is not running, they have more serious problems to address. One of my primary goals is to not affect anyone else around me - just to save the dinosaurs in any other way possible.

 

[Four Suns]

What if someone runs out in front of you?

 

[Hampton]

What if someone runs out in front of you?

I recommend using the brake and stopping the vehicle. After I shut the thing down, I can still steer very well until nearly stopped, and the brakes have accumulated power that keeps the power on them for 3 or 4 applications. I don't experience any degredation in control at all.

 

[fwebster]

Just by yourself a VW commuter car and triple your fuel mileage.....then you can save all that computing time for important stuff like reading the posts and enjoying the daily weirdness on CSR.

Actually, if you really get serious about reducing commuter cost, the VW turbodiesel runs quite well on homebrew biodiesel or WVO.........of course, either way, you have to listen to all the crap your friends give you about driving a teenage girl's car or a style deficient econobox.

 

[Hampton]

Actually, if you really get serious about reducing commuter cost, the VW turbodiesel runs quite well on homebrew biodiesel or WVO.........of course, either way, you have to listen to all the crap your friends give you about driving a teenage girl's car or a style deficient econobox.

You just can't win.

The truth is, it has more to do with finding a challenge and conquering it. Sure, the change in fuel cost is a big consideration and the main driving force, but the challenge is the,,,,, the challenge.

 

[Four Suns]

And here I thought the pilots were up there trying to figure out how to get me to my business meeting FASTER and instead they are trying to save FUEL! ugh.

Don't take this the wrong way, but I've never trusted "pilot math". For example, sitting on the runway in Atlanta, I can look out the window on a stormy afternoon and see/hear a plane take off every 3-4 minutes. The pilot will always get on the PA (Delta is the worst) and say "We are number 24 for takeoff so it should be another 20 minutes or so." Huh?

 

[comsnark]

And here I thought the pilots were up there trying to figure out how to get me to my business meeting FASTER and instead they are trying to save FUEL! ugh.

Yeah. . . trying to get you there faster. Which works in hand with the general airline policy of giving the passenger a joyous, comfortable travel experience.