This whole hypermiling thing’s been a popular discussion when we reporters and editors go out for lunch.

A couple of days ago, I posited this query: “Why does the gas needle drop faster after the halfway mark?”

I believe there was a chorus of “Yeah!?!?!?” that followed.

Thanks to the wonders of the Interwebs and its vast network of information (sometimes mis) there’s an answer.

Or should I say, several answers. Most of the answers based on the physical properties of gas tanks and electrical circuits make the most sense, though I won’t put this one out of the realm of possibility:

New car owners were complaining that the new cars were not getting good gas mileage. The manufacturers found out that if they made it take longer for the gauge to reach the half tank mark, the number of complaints was reduced.

I wonder what happens with these gas gauges.

“I don’t know of anything that says you can’t do that,” said Krista Hedstrom.

The Washington State Patrol trooper said she learned to drive doing it, and I’d just commented on how a lot of people ask me about it when I tell them I’m hypermiling.

“Do you coast down hills?”, people ask.

To the RCW book and online reference Hedstrom went.

“I’ve never had to look that up,” she said.

Sure enough, RCW 46.61.630 spells it out:

(1) The driver of any motor vehicle when traveling upon a down grade shall not coast with the gears of such vehicle in neutral.

(2) The driver of a commercial motor vehicle when traveling upon a down grade shall not coast with the clutch disengaged.

Now, let’s be clear, I’m not trying to make Trooper Hedstrom look silly for not knowing that one off the top of her head. If you look at the “Rules of the road” section in the state’s RCW database, you’ll quickly realize that no one probably knows EVERY traffic law. And realize that most of the laws you see have sub, sub-sub, and maybe sub-sub-sub laws.

I went to Hedstrom’s office this morning because I’ve wondered, and some have debated, what’s legal and what’s not, when it comes to hypermiling?

Laws vary from state to state, and I get the feeling a common sense approach is the best way to go about things.

Some more “advanced” techniques are no-brainers, when it comes to safety and legality. Drafting behind a semi? Take a guess. Cutting off your engine while coasting? If you can’t coast in neutral, again, take a guess?

“If you think in your mind it’s a bad idea, it probably is,” Hedstrom said.

During this experiment, I’ve agreed not to do anything illegal or crazy, so I suppose I’ll “coast” down hills in 6th. Even with that, there’s debate over whether in-gear engine braking or coasting in neutral uses more fuel. (Anybody have an answer?)

Every time we get behind the wheel, we take a calculated – or sometimes random – dose of risk in breaking or bending the rules of the road.

If you speed, you know you’re risking a ticket, or increasing the likelihood of a crash. One could say the same about coasting in neutral.

You exercise discretion in your driving style. Police exercise discretion in writing tickets.

“We don’t really have a choice what we pay for gas,” Hedstrom said.

When you can, choose wisely.

I know gas gauges aren’t the most accurate devices, but the view of the little red needle was nice when I pulled into work this morning. 120.9 miles so far. Usually it’s about 20 miles short of that mark.

All I’ve done so far is slow down on the freeway to just shy of 60 with the cruise control, pumped up my tires, and my standby cargo – in my case, golf clubs and a fair bit of junk.

If I get to 360 miles by my usual fill-up time, I’m looking at about 32-33 mpg. We’ll see.

Whenever you’re doing a pseudo-scientific study, baselines are important. You know, for science.

Actually, in the case of getting better gas mileage, it really makes sense. Will you know if you’re getting more MPGs if you don’t know how many MPGs you get now?

(Not to mention, tracking your mileage can give you early clues when something might be amiss with your lovely auto carriage.)

Here’s what I do: Set your trip odometer right after you fill up. Every time. I drive until my light comes on, which usually leaves me with between 10.8 to 11.2 gallons to fill it back up until the *click* of the auto shutoff.

Now’s where you look at your trip and enter the miles in your calculator. Virtually every cell phone’s got one, so no excuses. Divide by the number of gallons you put in, and viola!

Another good idea is to check your vehicle’s MPG rating at fueleconomy.gov to see how you stack up. Somehow, even with a slightly leaded foot, I manage better than my car’s 26 mpg estimate.

You should also note that if you still have your window sticker from your 1990 Chrysler New Yorker, disregard the MPG figure. The EPA has changed the way it calculates MPG and most numbers are now lower than the old system. The Web site has recalculated numbers for all the pre 2008 vehicles.(Including mine.)

Now you and I should have a pretty good handle on where we stand. Let’s hope the numbers go up next time at the pump.

I hate math, but these numbers have never been more important to me: 4.55, 49.14, 1950 and 28.

My high school math teachers would be so proud to see me hunched over my cell phone calculator every time I’m about to leave a gas station. This is where I wage my battle with numbers as I carefully plunk in numbers after a quick peek at the trip and the pump’s gallon readout, followed by a bit of advanced calculus (for journalists) called dividing.

Twenty-eight miles per gallon. Not bad. $49.14 for 10.8 gallons of premium $4.55-a-gallon fuel. Ugh. Even if gas stayed the same price (funny, huh?) for a 12,000 mile year of driving, I’d spend $1,950 on gas. I don’t even need the calculator to know I don’t like that number.

Now I have a new number in mind: 35. Miles per gallon that is. It’s a 25 percent increase in fuel efficiency. Doable. Again, assuming those figures, I’d save about $390 a year.

No, I’m not going to buy a new car. I’m going to employ some techniques of “hypermilers” who take a different approach to driving to squeeze out every last penny and wheel rotation from their fuel.

The premise is simple. I’ll take my car, a 2004 Pontiac Vibe GT (It requires the pricey premium fuel.), and drastically change the way I drive. Along the way, hopefully you’ll learn something, and I’ll give you honest observations about the monetary, logistical and psychological effects of hypermiling.

You and I, we’re probably pretty similar out there in the concrete jungle. I see you all the time. Accelerate too fast? Brake a little too late? Enjoy cruising at 67 (80 if you’re on I-5) on the highway? For most of us, driving habits like these are buried deep like a little petrol-slurping chigger under our skin.

The bottom line, is that the WAY we choose to drive can really save or cost us money.

Over the next few weeks I’ll be transforming my own driving, and proving links to gas-saving stories, making some videos, talking with local hypermilers, mechanics, you name it.

If you’ve got ideas, send them my way, and if you want to take this ride with me, keep track of your mpgs. We’ll see who makes the most progress. OPEC dares you.