Drafting = 3 mpg increase

[electricity_guzzler]

If i do cruise control 65mph I get about 48 mpg. But when I tried drafting 1 to 2 car-lengths behind SUVs at 70 to 80 mph, I get better gas mileage, about 3 mpg more.

This makes sense to me because air resistance is mainly what your spending energy on at highway speeds. At 65 mph cruise control, I'm the slow car and everybody passes me, so I'm not in anybody's draft and i'm getting the full frontal air resistance. If I drive with traffic even at a faster speed, I get less air resistance because I'm following another car's wake.

tip: look for SUV drivers talking on their hand-held cell phones. they tend to drive at a constant speed. whereas those who are not distracted tend to accelerate/decelerate often. also drivers on cell phones tend not to change lanes when somebody is drafting them. drivers who are not distracted will think that you want to pass and either accelerate or change lanes.

[NuShrike]

[quote=electricity_guzzler @ May 25 2006, 01:07 PM) [snapback]261025[/snapback]</div>

If i do cruise control 65mph I get about 48 mpg. But when I tried drafting 1 to 2 car-lengths behind SUVs at 70 to 80 mph, I get better gas mileage, about 3 mpg more.

This makes sense to me because air resistance is mainly what your spending energy on at highway speeds. At 65 mph cruise control, I'm the slow car and everybody passes me, so I'm not in anybody's draft and i'm getting the full frontal air resistance. If I drive with traffic even at a faster speed, I get less air resistance because I'm following another car's wake.[/b]

Drivers on cell phones will also suddenly stop without warning due to their lack of frontal attention. Vehicle A can stop much faster than following Vehicle B if A hits something.

Meantime, check your tire pressures and oil level. I consistently get ~48-50mpg (39/37psi) with cruise] 65mph (102 km/h). I get even better drafting big rigs (at 2-3 car lengths), but it could be just the 87-99 km/h speed.

[MikeSF]

tip: don't tail gate anyone that's just bad karma, get your fuel efficiency elsewhere... like driving less than 70-80mph. prius owners dont like it when SUVs tailgate them, I doubt they like very much anyone tail gating them

[burritos]

<div class='quotetop'>QUOTE(MikeSF @ May 25 2006, 06:56 PM) [snapback]261092[/snapback]</div>

tip: don't tail gate anyone that's just bad karma, get your fuel efficiency elsewhere... like driving less than 70-80mph. prius owners dont like it when SUVs tailgate them, I doubt they like very much anyone tail gating them
[/b]

Maybe all them suv's that tailgate us are just drafting to improve their crappy mpg?

[cwerdna]

I think what the OP is suggesting is a very bad practice and potentially very dangerous. One car length is too close at those speeds. Two is somewhat marginal but you sometimes can't help it due to congestion.

I try to drive defensively. (reminds me that I should try to look around for a defensive driving course) Personally, if I can help it if there are multiple lanes, I like to have a LOT of room in front of me. I try to switch to empty lanes when possible or to lanes where I have a LOT more room in front of me.

Even if the increase in mileage were 50%, I don't think it'd worth the danger. An accident could cost you a heck of a LOT more than what the gas savings over the life over the car.

[electricity_guzzler]

WOW! I just tried drafting behind an 18-wheeler this morning. incredible mpg gain. 10mpg more. The good thing about drafting big trucks is that you know they cannot brake faster than you can. From now on, i'm taking the truck lanes everyday!

[DaveinOlyWA]

you are playing with fire

[KD6HDX]

I tried this morning following a 40 foot trailer. He was driving 55 MPH. Sometimes he was slowing down to 51-52 and then back up to 55MPH. Two to three car lengths at this speed did seem to give a little more MPG on the MFD. But it was over a half hour period on the way to work this morning. Overall, I would say it is a risky bet for a few pennies gained. Especially at 70 or 80 MPH. My wife was asleep on the commute this morning. Had she been awake I would never have tried this experiment. A little later down the freeway, I pulled in behind another prius in the slow lane going 52 MPH. I stayed behind him for about 10 miles. The slower speeds are what I think are giving the increased MPG's. Like I have said in the past, when I drive tha carpool lanes at 70 MPH, I get about 48 MPG. When I slow down and cruise at 55, I get about 53 MPG. I will not cruise at 55 mph in the carpool lane. This really pisses off people and since I live in So Cal, I may not be able to reload fast enough!

The best way to streamline the prius is to fold back its rear view side mirrors. This reduces the drag coefficient even more. Plus it makes the car look more goofy and people around you will slow down too when they try to tell you your mirrors are folded back.

Dave 2005 PRIUS
Reducing my dependency on American oil from foreign lands one goofy little car at a time....

GO BIG ED ON AIR AMERICA

[hycamguy07]

<div class='quotetop'>QUOTE(electricity_guzzler @ May 26 2006, 10:24 AM) [snapback]261292[/snapback]</div>

WOW! I just tried drafting behind an 18-wheeler this morning. incredible mpg gain. 10mpg more. The good thing about drafting big trucks is that you know they cannot brake faster than you can. From now on, i'm taking the truck lanes everyday!
[/b]

Here its 181.50 + 4 points on your license..

The only difference is other people call in on their cellphones and follow you until an officer arrives

Another cool thing for drafters is running over tire sherapnel and 1 -2 car lengths is not enough reaction time before the drafter hits the debris..

[brandon]

<div class='quotetop'>QUOTE(electricity_guzzler @ May 26 2006, 09:24 AM) [snapback]261292[/snapback]</div>

The good thing about drafting big trucks is that you know they cannot brake faster than you can.[/b]

Of course, that doesn't matter much if when they can't see that you're riding their a$$ behind their trailer. Even if they hit the brakes, you still have to allow yourself enough distance that you can react to it. Please re-read posts on other threads where you were advised to drive defensively...

We're not trying to put you out, we just don't want you going out and killing yourself and/or others for the sake of a few extra MPG.