Slipstream ???? you mean "tail gating" -

http://en.wikipedia.org/wiki/Tailgating

..you may save on gas but increase your chances of detroying 2 cars. And what will that cost.....

Also tailgating causes you to break more often and have to press on the gas again.

Just slow down - avoid jack rabbit starts, and racing up to the red light. better yet - work form home a few days a week.

Not really tips to cut down on consumption, more like alternatives to the car...

-- Get a two-wheeler for trips where you drive the car alone. Preferably an electric but at least with a 4-stroke engine.

-- Use a bicycle for short trips.

-- Convert your car into an electric. It isn't very hard to do and doesn't have to be too expensive. If range is an issue, get permission to have it charged at work.

-- If you have a very long commute, look for work close to your home or move close to your work.

-- If much of your job involves the computer and the phone, try convincing your company for letting you work from home as an experiment...say, two days a week.

-- Offset your car's emissions by buying TerraPass.

-- Carpool and if you can't find a partner, look for creative ways such as putting up an ad on Craigslist.

What about "get rid of your [not so efficient] car and join Flexcar instead"?

From their latest member newsletter:
"Flexcar's environmentally friendly fleet already achieves 40% better fuel economy than the average new vehicle sold in the US. And with nearly 500 hybrid vehicles, Flexcar now has the "coolest" fleet in the industry."

Plus, they have a partnership with Terrapass through which you can offset the miles you drive each year.

Slipstream can be several car lengths behind. Just like in nascar were a car 20 30 car lengths behind leader pick up the draft(slipstream) and get pulled forward.

The car infront of you is doing all the work breaking the air. Your just cruising behind using less gas driving calm, braking and accelerating smoothly. Not only will these small things save you some gas, but you'll see reduced parts wear.

drive a manual...
most manual cars get better gas mileage on average, and allow for creative ways to save even more, namely coasting when possible so the engine is only idling. They are also easier to shut off for short amounts of time as you don't have to shift into park before you do it (this may be different on new manual cars that require you to brake and be in neutral and all that before starting).

@Rogers Place:

On normal road driving under normal conditions, in order to get a fuel consumption benefit from drafting even something with a massive wind profile like an eighteen wheeler, you have to drive closer to the vehicle than is safe to do. This was recently demonstrated and quantified on an episode of Mythbusters, actually. The roads aren't Nascar.

@ Rhett (Greentime): I saw that episode of Myth Busters and even @ 100 ft behind a semi, you still recieve significant MPG savings. An average car is 10-15ft long so 100ft is 7-10 car lengths. I don't know about else where, but the triffic on the expressways around Chicago travels WAY closer than that going 60-80 mph, behind semis and all.

Definitely ride your bike whenever possible

+1 drafting trucks:

I have made an hour long drive (1-way) a handful of times this summer and have gotten up to averaging 35mpg by driving slowly until I'm passed by a semi to follow.

I follow at my normal, safe distance and there is a noticeable decrease in drag (I drive a convertible and not nearly as much wind noise/turbulence).

Driving manual is much better.
Newer cars don't seem to impose stupid things like braking before shutting of the engine or starting it. As a matter of fact neither do automatic. Even with automatic, when I wanted to coast, shift to neutral - you don't even have to press the button, as between neutral and drive, you can switch just by moving the stick.

So if you're in coasting downhill, switch to neutral, and you can even turn off your engine if you wanted - and then start it when you want again (still talking about automatic) while the car is in neutral.

Of course manual drivers are much more used to this sort of shifting then automatic drivers are, but I just wanted to explain it's doable.

Now before you flame me, I wanted to mention that yes, if you turn your engine off on a highway, whether manual or automatic, you will loose power steering and power braking. So I would recommend it on a highway ONLY if it's near empty. However I found it safe enough on smaller roads (especially hilly ones) and on long red lights (especially if it's your daily route and you know you just got a red light and it will take 2 minutes to switch to green).

I've read somewhere that if you have the right tire pressure and drive the right way (coast to a red light, for instance) you could achieve up to 40% more gas efficiency.

I turn off my car aggressively, even learned to drive without power steering or braking - but I stress I do it only on calm roads - with less traffic). I definitely shut off the engine when approaching a parking booth attendant and at red lights. It works great.

Anyone seen the Mythbusters on riding a slipstream (Drafting)? Just don't do it... not safe

Be very careful about coasting. Your transmission needs lubrication and that is accomplished by a pump in the input shaft so coasting and shutting off your engine can cause a lack of lubrication since there is nothing to move the fliud around.
Also with a modern fuel injected engine coasting with the engine ideling can use more than leaving it in gear. When your going downhill in gear the weight of the vehilce is doing some work turning the engine and the engine computer will cut back on the injector pulse width and actually use less fuel.

While drafting can be unsafe, I have gotten my best gas milage by following the big trucks at a safe disatnce. This is more due to the slow up hills and fast down hills they do rather than trying to maintain their speed. So instead of giving more gas to get up the hill you let your speed slow down then let it speed back up going down the other side. When I made those long trips home while in college I save a bit of $ even when gas was still a $1 per gallon.

Also, drafting off a truck increases the truck's fuel consumption, because the more turbulent their wake, the more drag they suffer. No net saving.

I can attest that except for the excessive speed negating it everyone in chicagoland seems to like slipstreaming. Coming from a small town in NS it sometimes scares the crap out of me. :-)

I really wouldn't mess around with the shutting off of your engine. There are times when you can avoid an accident by driving out of trouble or needing to swerve quicker than not having the PS boost there to help will let you. Example, coasting down a long hill and all of a sudden someone pulls out of a driveway right infront of you, panics and hits the brakes blocking your lane. My reaction would be to brake and swerve around them but with the power dead both steering and braking are hindered. In short don't do it. Coasting out of gear is OK but on some hills engine braking is better than wearing out your brakes.

Hybrid cars can safely shut off their engine because they have electic PS and the brake boost not using engine vacuum.

"Also, drafting off a truck increases the truck's fuel consumption, because the more turbulent their wake, the more drag they suffer. No net saving."

Any proof of this, because I find this very unlikely. Common sense, and what I know of physics/engneering, would suggest otherwise.

On most of the roads around me (NJ) its very hard NOT to be 100ft from a semi a lot of the time.

I have been told that some cars have suspension adjustments which assume the car is under power. Coasting may leave a car more twitchy and less safe. Your car, your judgement.