drafting off 18 wheelers doesn't seem to help much

[ElFenix]

175 miles on the way to austin and a little driving around netted me 6 2/3 gallons used. on the way up i was speeding the whole way, at times hitting triple digits when convoying with a 740 and some F150s.

on the way back, i drove 165 miles and used 6 1/3 gallons. on the way back i sat behind 18 wheelers as much as i could, with the needle pegged at the speed limit.

so, in my car, speeding gets better mileage than drafting. of course, the difference in gas pumps is probably the reason for this. my gas needle was above the halfway mark after driving back, but quite a bit below on the way up (not that the gas gauge is at all accurate).

all in all, without something like adaptive cruise control that will keep me safely off the truck's bumper but within drafting range, driving like that is more tiring than the couple of bucks in potential savings is worth.

 

[NutBucket]

Watch Mythbusters, draft a big rig and report back

EDIT: I'm a moron. How is this a good comparison if you didn't drive the same speeds under both scenarios. Apples & Oranges.

 

[ElFenix]

Originally posted by: NutBucket
Watch Mythbusters, draft a big rig and report back

i read the synopsis of that episode. that's why i tried doing it. whatever gas savings there were probably got eaten up by differences in the gas pumps. i might not have been close enough, but tailgating 18 wheelers isn't exactly a stress-free driving method.

i also tried to pulse and glide when i wasn't behind 18 wheelers, and that is a pain in the ass. especially on hilly roads.

 

[NutBucket]

How close were you following. At 100 ft. I believe the it worked about to about 10% more efficient. The most gains were found at 20 ft:Q

 

[Zenmervolt]

First of all, drafting really doesn't begin to have an impact until about 75 mph or more.

Second, you'd need to be 15-20 ft from the back of the semi to be in the low-pressure are ("the draft"), if you're farther back than that, you're in the trailing vortexes and you're suffering from increased drag instead of decreased.

Essentially, to draft in a manner that would actually save fuel would be pretty damn dangerous.

ZV

 

[jagec]

Wait, you're trying to report fuel savings based on GAS GAUGE readings? That doesn't work. This is what you do.

Fill your tank all the way. Zero your trip meter.
After driving, fill your tank again, all the way. Write down the number on your trip meter, and zero it for the new tank. Divide the miles by the number of gallons it took to fill, and report back.

 

[Gillbot]

Originally posted by: Zenmervolt
Essentially, to draft in a manner that would actually save fuel would be pretty damn dangerous.

ZV

+1, no way i'd want to follow that closely at high speeds.

 

[Eli]

I noticed a huge difference while drafting behind a semi.

I noticed that it depended on what type of semi I was behind. I found it was best with a truck that had a low to the ground trailer... one of the types that drop its load from the bottom. If the trailer was too high up, I could feel the turbulence from under the truck hitting me, since my car is so low in comparison.

I was also only about 5-10 feet from the back of it. This took intense concentration. It's not something I would do all the time.

You could really feel it, though. If I backed off too much, I could immediately feel the increased wind resistance and turbulence blowing me all over.

 

[Crafty35a]

Originally posted by: Eli

I was also only about 5-10 feet from the back of it. This took intense concentration. It's not something I would do all the time.

5-10 feet?? That's god damn insane.

 

[GoatMonkey]

What they need to do is make trucks and trailers out of plexiglass so you can see through them when you're tailgating. Of course these trucks would also have to drive around with nothing in the trailer either. Or if you could get Wonder Woman to drive in front of you with her invisible truck that would work too.

 

[Demon-Xanth]

I've found that the amount that you save in gas ends up being spent on windshield repairs.

 

[ElFenix]

Originally posted by: jagec
Wait, you're trying to report fuel savings based on GAS GAUGE readings? That doesn't work. This is what you do.

Fill your tank all the way. Zero your trip meter.
After driving, fill your tank again, all the way. Write down the number on your trip meter, and zero it for the new tank. Divide the miles by the number of gallons it took to fill, and report back.

i did that. how else would i know that i used 6 2/3 gallons on the way up and 6 1/3 gallons on the way back?

the gas gauge needle discussion was due to my suspicion that the pumps didn't fill to the same level.

Originally posted by: Zenmervolt
First of all, drafting really doesn't begin to have an impact until about 75 mph or more.

Second, you'd need to be 15-20 ft from the back of the semi to be in the low-pressure are ("the draft"), if you're farther back than that, you're in the trailing vortexes and you're suffering from increased drag instead of decreased.

Essentially, to draft in a manner that would actually save fuel would be pretty damn dangerous.

ZV

go read a synopsis of the mythbusters episode. no idea what speed they tested at, though

 

[imported_Truenofan]

"Fill your tank all the way. Zero your trip meter.
After driving, fill your tank again, all the way. Write down the number on your trip meter, and zero it for the new tank. Divide the miles by the number of gallons it took to fill, and report back. "

actually what you could do, is fill you tank of course, yes you can reset your trip, but that can always be off due to tire sizes(it wont be much for short distances, but longer it can be off by more or less). you drive where you need, then fill up again, take note as to how many gallons you used, and then take the trip and do the math.

http://www.fueleconomy.gov/mpg...?action=purchaseRecord

 

[overst33r]

Originally posted by: Truenofan
"Fill your tank all the way. Zero your trip meter.
After driving, fill your tank again, all the way. Write down the number on your trip meter, and zero it for the new tank. Divide the miles by the number of gallons it took to fill, and report back. "

actually what you could do, is fill you tank of course, yes you can reset your trip, but that can always be off due to tire sizes(it wont be much for short distances, but longer it can be off by more or less). you drive where you need, then fill up again, take note as to how many gallons you used, and then take the trip and do the math.

http://www.fueleconomy.gov/mpg...?action=purchaseRecord

Your odometer is affected by the same characteristics you mentioned... I don't see how that is easier to do than using the trip meter, if anything you add an additional step.

How come you never use the quote button?

 

[jtvang125]

Originally posted by: Demon-Xanth
I've found that the amount that you save in gas ends up being spent on windshield repairs.

Not to mention the front bumper and hood. They must look like they got sand blasted.

 

[jagec]

Originally posted by: mariok2006

Originally posted by: Truenofan
"Fill your tank all the way. Zero your trip meter.
After driving, fill your tank again, all the way. Write down the number on your trip meter, and zero it for the new tank. Divide the miles by the number of gallons it took to fill, and report back. "

actually what you could do, is fill you tank of course, yes you can reset your trip, but that can always be off due to tire sizes(it wont be much for short distances, but longer it can be off by more or less). you drive where you need, then fill up again, take note as to how many gallons you used, and then take the trip and do the math.

http://www.fueleconomy.gov/mpg...?action=purchaseRecord

Your odometer is affected by the same characteristics you mentioned... I don't see how that is easier to do than using the trip meter, if anything you add an additional step.

How come you never use the quote button?

I suppose you could use a GPS if you're that concerned about it...but a couple percent really isn't a big deal to me. So my car actually gets 32.4 instead of 33 MPG, big whoop...

 

[NutBucket]

Originally posted by: ElFenix
go read a synopsis of the mythbusters episode. no idea what speed they tested at, though

55 mph

 

[DanTMWTMP]

I get significant fuel savings when i put it on cruise and RARELY feather the pedal. I get higher fuel savings when cruising around 85 mph then when "trying" to keep my foot steady @ 65 (both yield me around 30). I get ultra high fuel savings when doing 65 w/ cruise control (about 32+). I haven't tried drafting constantly, but it should help AS LONG as you do cruise control and try not to match the speed (since that involves feathering the pedal).

EDIT: w/ Mazda3 2.3.

 

[ElFenix]

Originally posted by: DanTMWTMP
I get significant fuel savings when i put it on cruise and RARELY feather the pedal. I get higher fuel savings when cruising around 85 mph then when "trying" to keep my foot steady @ 65 (both yield me around 30). I get ultra high fuel savings when doing 65 w/ cruise control (about 32+). I haven't tried drafting constantly, but it should help AS LONG as you do cruise control and try not to match the speed (since that involves feathering the pedal).

EDIT: w/ Mazda3 2.3.

my cruise control is stupid and 'floors it' uphill.

when i had a taurus i found that by keeping my foot at a constant position (and ignoring the effect that hills had on my speed) i got better mileage than using cruise.

 

[Black88GTA]

Originally posted by: ElFenix

Originally posted by: DanTMWTMP
I get significant fuel savings when i put it on cruise and RARELY feather the pedal. I get higher fuel savings when cruising around 85 mph then when "trying" to keep my foot steady @ 65 (both yield me around 30). I get ultra high fuel savings when doing 65 w/ cruise control (about 32+). I haven't tried drafting constantly, but it should help AS LONG as you do cruise control and try not to match the speed (since that involves feathering the pedal).

EDIT: w/ Mazda3 2.3.

my cruise control is stupid and 'floors it' uphill.

when i had a taurus i found that by keeping my foot at a constant position (and ignoring the effect that hills had on my speed) i got better mileage than using cruise.

:laugh: The entire purpose of the cruise control is to keep the car moving at a preset speed. It adjusts the throttle as necessary to do that as driving conditions warrant (altitude, hills, temperature, etc). You need more throttle going uphill to keep a constant speed vs. a flat road.

You may get a tiny bit better mileage keeping your foot position constant, but if you do this, inclines will scrub off your speed and you'll only end up pissing off other drivers behind you when you drop 15 mph going uphill.

It kills me how so many people spend all of their time worrying about squeezing out the absolute highest mpg possible - even pulling dangerous stunts like tailgating 18 wheelers or slowing down considerably on hills, etc. to do so - all in the name of 1-2 more MPG. And everyone seems OK with this. Yet, as soon as someone admits to going 10 mph over the limit, or (god forbid) has a single beer at a party and drives home - the lynch mob is here with their torches and pitchforks, calling for the offender's head.

 

[nweaver]

Originally posted by: Black88GTA

Originally posted by: ElFenix

Originally posted by: DanTMWTMP
I get significant fuel savings when i put it on cruise and RARELY feather the pedal. I get higher fuel savings when cruising around 85 mph then when "trying" to keep my foot steady @ 65 (both yield me around 30). I get ultra high fuel savings when doing 65 w/ cruise control (about 32+). I haven't tried drafting constantly, but it should help AS LONG as you do cruise control and try not to match the speed (since that involves feathering the pedal).

EDIT: w/ Mazda3 2.3.

my cruise control is stupid and 'floors it' uphill.

when i had a taurus i found that by keeping my foot at a constant position (and ignoring the effect that hills had on my speed) i got better mileage than using cruise.

:laugh: The entire purpose of the cruise control is to keep the car moving at a preset speed. It adjusts the throttle as necessary to do that as driving conditions warrant (altitude, hills, temperature, etc). You need more throttle going uphill to keep a constant speed vs. a flat road.

You may get a tiny bit better mileage keeping your foot position constant, but if you do this, inclines will scrub off your speed and you'll only end up pissing off other drivers behind you when you drop 15 mph going uphill.

It kills me how so many people spend all of their time worrying about squeezing out the absolute highest mpg possible - even pulling dangerous stunts like tailgating 18 wheelers or slowing down considerably on hills, etc. to do so - all in the name of 1-2 more MPG. And everyone seems OK with this. Yet, as soon as someone admits to going 10 mph over the limit, or (god forbid) has a single beer at a party and drives home - the lynch mob is here with their torches and pitchforks, calling for the offender's head.

Drinking and driving should be cause for a lynching. There is a reason, IT KILLS PEOPLE.

Inconveniencing people with poor driving habits is not nice.
Drinking and driving and possibly killing people is just a little up the "not nice" scale from that. If you don't understand why, then please find the nearest vertical dropoff and replicate DaVinci's flying machine.

 

[ElFenix]

Originally posted by: Black88GTA

:laugh: The entire purpose of the cruise control is to keep the car moving at a preset speed. It adjusts the throttle as necessary to do that as driving conditions warrant (altitude, hills, temperature, etc). You need more throttle going uphill to keep a constant speed vs. a flat road.

no sh!t, sherlock. that doesn't mean it should floor it and drop two gears every time it goes uphill.

 

[Zenmervolt]

Originally posted by: nweaver

Originally posted by: Black88GTA
or (god forbid) has a single beer at a party and drives home - the lynch mob is here with their torches and pitchforks, calling for the offender's head.

Drinking and driving should be cause for a lynching. There is a reason, IT KILLS PEOPLE.

Inconveniencing people with poor driving habits is not nice.
Drinking and driving and possibly killing people is just a little up the "not nice" scale from that. If you don't understand why, then please find the nearest vertical dropoff and replicate DaVinci's flying machine.

A single beer does not make anyone drunk. Reading comprehension please.

ZV

 

[nweaver]

Originally posted by: Zenmervolt

Originally posted by: nweaver

Originally posted by: Black88GTA
or (god forbid) has a single beer at a party and drives home - the lynch mob is here with their torches and pitchforks, calling for the offender's head.

Drinking and driving should be cause for a lynching. There is a reason, IT KILLS PEOPLE.

Inconveniencing people with poor driving habits is not nice.
Drinking and driving and possibly killing people is just a little up the "not nice" scale from that. If you don't understand why, then please find the nearest vertical dropoff and replicate DaVinci's flying machine.

A single beer does not make anyone drunk. Reading comprehension please.

ZV

It CAN make someone drunk and DOES impair driving (even if only a little). Driving after drinking ftl

 

[Gillbot]

Originally posted by: nweaver

Originally posted by: Zenmervolt

Originally posted by: nweaver

Originally posted by: Black88GTA
or (god forbid) has a single beer at a party and drives home - the lynch mob is here with their torches and pitchforks, calling for the offender's head.

Drinking and driving should be cause for a lynching. There is a reason, IT KILLS PEOPLE.

Inconveniencing people with poor driving habits is not nice.
Drinking and driving and possibly killing people is just a little up the "not nice" scale from that. If you don't understand why, then please find the nearest vertical dropoff and replicate DaVinci's flying machine.

A single beer does not make anyone drunk. Reading comprehension please.

ZV

It CAN make someone drunk and DOES impair driving (even if only a little). Driving after drinking ftl

I'm gonna have to agree on this one. I NEVER drink so one drink could impair my reaction time considerably and all the while I may not be legally "drunk".