Full tank was 44.8 calculated (0.2 below the displayed average at the end of the trip), but considering it was about 40% drafting, 40% cruising, 10% city (at the ends) and 10% mountain passes, it's somewhat irrelevant in the context of this thread.

 

I'm a bit surprised at how upset some people got about this question. I live in the SF Bay area and as a part of my regular commute I'd estimate that 75% of cars are tailgating within 25 feet at 65 mph and around 20% (yes I mean 1 in 5) are tailgating at under 15 feet at 65 mph. I see at least 5 tailgaters less than 10 feet at around 60 every day. Around here if you actually leave 2 or more seconds between you and the car in front of you, you will soon find two or more cars changing lanes into that space. Shen you slow down so you aren't tailgating these new cars and a few more pull in. After a few more iterations, cars behind you are whipping around, flipping you the finger, and pulling in front of you as you continue to slow to maintain a safe distance. Soon enough you are doing 40mph in the fast lane.

Following 30 feet behind a big truck can yield big mpg gains and is much safer than simply getting on any local freeway during a typical rush hour.

 

Uh, no.
NO.
First of all, just because people do stupid stuff doesn't make it less stupid.
Second, you can see past a car in front of you. You can't see through a truck, so if the vehicle in front of him slows down, you won't know it. And if he's on the phone, or tired, or whatever- if he doesn't slow down until it's too late, you're toast.
Third, speaking of toast- if the car in front of you weighs twice what your Fit weighs, you absorb most of the impact. If it's a truck that weighs 20 X your Fit, you
are
toast.
Third, people may tailgate in traffic, and get in front of you if you leave space- but that's not during all your driving.
Fourth, if it's in traffic it's probably not at 65 mph...


I can't speak for SF, I don't drive there, but here in NY it's not all that common that many people are within 10 or 15 feet. Too close, yes, but not 15 feet, that's LESS THAN A CAR LENGTH.
RARE that someone's that close.


If you crash, it drives up my insurance rates.

 

Nobody flips me the bird and I always leave space, at least two seconds at freeway speed. Occasionally people cut in... that's ok. If you're having these problems it's probably a confidence image you're giving off that shows you're an easy target. Yes, serious. I can spot one a mile away when i'm coming up the onramp into freeway traffic and need to merge.

When driving a car like a Fit you need to compensate for it's small size and non-threatening appearance with a boatload of driving confidence lol I never have to drive like that when i'm in a full-size car, people don't even try to get in front and generally just let me in when I signal.

 

People get too excited about exact percentage gains and distances more suited to parallel parking or Nascar, but that's not what it's about. Up here we don't have too much in the way of open road so you're generally behind someone. We've all been behind someone before and lived through the experience.

With good instrumentation, you can see differences in mileage before you have to go to the gas station. With the cruise on, you can watch your mileage jump when a car passing you pulls back in, and then watch it slowly drop back down as that car pulls away. You can watch your mileage slowly pick up as you gain on someone and then drop when you pull out to pass. You can see this often enough to see the connection between your mileage and being behind someone. Even without instrumentation you can notice that your glides don't lose speed as quickly when there's someone in front of you.

Trying to pin things down to "at speed X in weather Y and distance Z, my mpg is A% higher than in the open, while at 0.5 Z, my mpg is B% higher" is ridiculous, and that's where most drafting arguments wind up: with people citing distances and speeds. No-talent ass clowns like Mythbusters don't help things by trying to show how much of a gain you can get at what distance. Those idiots could screw up a free lunch.

It's easy to observe that all things being equal, having someone punch a hole in the air for you tends to help raise your mpg. None of this calls for a death wish, or at least any more of one than it takes to get out there in a tiny little car that fails the "large concrete block" crash test. How about this:
1. Traveling too close behind someone is dangerous no matter what your goal is.
2. Being behind someone at a reasonable distance can be good for gas mileage.

If you can't figure out what a reasonable following distance is without using a speed/distance chart and a tape measure, then you're dangerous no matter what you do so don't call it hypermiling.