You hear a sharp, metallic crunch. Peeling your face from the van’s back window, you start spitting slivers and pebbles of teeth, and scream for a friend: ‘John?! John!’

Really, this has always been a double-edged dream of mine. Badass, mutant motorcyclists like in ‘Raising Arizona’ or ‘Mad Max’ encouraged me to get on a bike, while shockumentaries akin to ‘Red Asphalt’ kept me off.

A motorized bicycle is the cupcake realization of that dream.

Attending a commuter college like CSUN further drives money loans to the stake, so testing gas conservation methods time-to-time becomes a necessity.

‘Just start pedaling,’ says my friend John DuBois in front of his Van Nuys house. ‘Once you have enough momentum release the clutch, and it will rev up.’

DuBois’ bike is modified with a 50cc engine. Given our weight, it could reach speeds of 30-35 mph.

‘Not exactly sure if it’s street legal,’ he says. ‘But anytime I see a cop car, I slow down and begin pedaling.’ Which works if police don’t notice the exhaust pipe, one-gallon gas tank, chassis, filter, sparkplug, and two-stroke engine mounted to the frame.

When DuBois told me he had a motorized bicycle I expected a cruiser match up of Corey Haim’s wheelchair from ‘Silver Bullet.’ The reality wasn’t far off, but the gears were mildly resistant, and the seller who gave DuBois a discount removed the kill switch in exchange.

If this works for me it could mean 70-mpg and no parking permit. So I straddle the cruiser, mindful of the warm exhaust, and pedal. Within moments I amp the throttle, and I’m putt-putting down residential streets with ease.

Confidently riding at 15 mph, I puff out my chest and announce I’ll be going around the block. I get to the intersection and forget to look both ways ‘hellip; and then I forget everything, and the brake and clutch operations swish in my brain’s rinse cycle. I speed up, 20 mph’mdash;a wide left and a thought passes quick, ‘Oh, shit. I’m going to crash.’

When I realize what’s happened, I feel the sharp sting of air brushing against nerves and pulp in my mouth. There’s no blood, but there’s a hole in my grin large enough for a cigarette.

After six hours of root canal drilling and crown filing on my front tooth, I was told I could never have corn on the cob again. In comparing useless appendages to restricted foods, this is worse than losing my pinky toes.

‘But how was the bike?’ people keep asking when I relay the Tooth Story. To be fair: It’s orgasmic!

Given, if people install a four-stroke engine to cutback emissions and a kill switch to safeguard teeth, motorized bicycles are efficient and legal (if kept under 20 mph). And people that have a two-stroke should invest in a catalytic converter, which will reduce smog by 80 percent.

However, sitting in that dentist chair for eternity got me thinking about practical ways to scrimp on $4-per-gallon gas.

There’s always using cruise control on freeways. Maintaining a steady speed could cut consumption, if only the 405 and 101 weren’t stop-n-go with clueless drivers.

And thanks to ‘MythBusters,’ I know that at 55 mph my AC should be off and the windows down. According to the Alliance to Save Energy, a coalition of various groups, an AC on max can reduce your miles per gallon by 5 to 25 percent.

Meanwhile, getting rides from my 17-year-old sister has shown me that she’s inherited our parents’ psychotic mannerisms. The muzzled shouts. The limitless entitlements. The swear words and tailgating.

They’d be better drivers with a straightjacket.

But their ever-common jackrabbit starts were worth testing for fuel efficiency.

My dad and I drove the family’s Toyota Sienna on a relatively flat street with a 3 percent incline, tracking the rate of acceleration on the overhead console. Covering the same distance of 0.95 miles, we varied from normal driving habits to ridiculously conservative (Sunday driver) to jackrabbit starts.

The difference between law-abiding techniques and Sunday driver status were minimal. We timed the normal speed at 1:33. The frantic, jackrabbit pace was clocked at 1:24. Altogether, we saved 3.5 mpg by driving civilly.

There is, of course, the trip computer add-on for the car. One of the more popular fuel economy calculators to come around is called ScanGuage ($169). It gives on-board diagnostics, going as far as troubleshooting the car whenever the ‘check engine’ light flashes. The 3-in-1 gauge also calculates gas cost per mile (so it’s nice to have a tissue box as money expels from the exhaust).

Still, it sucks when we have to be ‘everything’ conscientious. When is it not hard times? There always seems to be something economically screwed in America, and some people go as far as ‘hypermiling’ to save gas.

If you’re unfamiliar with the term, I don’t recommend it. If you feel brave, shift the car into neutral and turn off the engine while coasting to a stop. (Highly dangerous!)

The only positive outcome in my gas-saving scheme was a phone number from the dental technician fixing my tooth, Savanna.

Head craned back and mouth open, I watch as she matches various shades of porcelain teeth, grouped like an African kalimba, to my remaining front tooth.

‘Can I get a tattoo on my replacement?’ I ask her, which starts a long conversation. Anyone willing to look at my mouth under a high-powered magnifier and still be flirtatious is good in my book.

So, I can’t have corn on the cob. In trying to save gas, I’m paying a year worth in dental bills. Want good mileage? Inflate your tires. Otherwise, you might become an anguished dunce.