Sometimes, a full bladder is more important than a full tank.

As all five of my regular blog readers have no doubt surmised, I recently took a vacation and, like any flag-waving American, I drove.

And before you roll your eyes and ask yourself, Oh God, is this going to be another blog where he waxes romantic about his beloved hybrid, allow me to answer you -- yes!

The trip to Roanoke takes, on average, six hours, most of them spent on the macadam roller coaster known to federal officials as I-81.

And needless to say, I was watching the mileage gauge like I work for Consumer Reports, an obsession which other occupants of the car have begun to worry might keep me from paying any to most important traffic regulations.

I've been experimenting with different speeds and, as my lovely wife Karen theorized, it turns out running the Civic at something more than 55 miles per hour actually improves the mileage over the long haul. The designers must be realists.

No slouch in the "my theory" department, my panicked theory that the mileage would improve in the summer when the engine did not have to warm up, has also proven true.

Armed with this knowledge and a featherweight foot, we achieved admirable but unremarkable mileage on the way down, but climbed near a personal best on the return trip.

I gazed in gleeful amazement as the mileage calculator climbed closer to 50 miles per gallon.

Have I mentioned that my life loves Diet Pepsi? She does.

She drinks it in the morning the way I drink coffee, which is to say a lot.

(This is not the place to discuss how my coffee mugs are reusable and her plastic bottles -- all recycled -- are not, but rest assured, this discussion has occurred.)

Anyhooo, as my feverish eyes gazed at the gauge and my sweaty hands (made so by my refusal to use the air conditioning) struggled to keep a grip on the wheel, we reached 49.9 miles per gallon.

And then, disaster struck in the form of too much Diet Pepsi and a failure to make my passengers don adult diapers as if we were astronauts driving all night bent on breaking a love triangle.

"But I'm almost at 50" I told my squirming, cross-legged betrothed. "Once we get off the highway, the whole thing we be fukakta," an Indonesian word I learned which I'm told means "slightly askew."

But mother nature, not to mention the mother of my child, is not to be denied and so we pulled into the Liberty station and my average was shot.

It got close once back on the highway, but we had already decided to pull off to see Luray
Caverns and the ride over and back over the Blue Ridge, it really is just this RIDGE in the middle of everything, made 50 mpg just a dwindling dream.

But hey, more than 400 miles later, I'm still tooling around Pottstown on the same 11 gallons I pumped down the hill from my father-in-law's house, so I'm not complaining.

By the way, Luray Caverns, said to be the largest on the East Coast, are truly a wonder to behold, made more magnificent by the fact that as far as I can tell, they are one of three things not threatened by global warming.

They are privately owned and therefore have just the right amount of chintzy tourist-trap crap to make me treasure it as an example of pure Americana, so I dutifully bought a T-shirt and my son a solar-powered key chain that blinks his name without batteries.

Laugh if you will, but this place has a "stalactite organ" that plays several times a day. In your FACE Crystal Caverns!.

Anyway, there's a long-overdue shout-out to bring up while I'm writing about driving.

I have a loyal reader and frequent correspondent in Thomas Mounce of Birdsboro. We first met over the 2004 election in which his candidate won the election but I won the "who will be the most unpopular president in history?" contest.

And whenever I pat myself on the back for buying a hybrid before the tax break expired, he writes to remind me that he drives a Volkswagen diesel that makes like a million miles per gallon.

OK, I exaggerate, but he is as devoted to his automotive choice as I am to mine. And while I have my doubts about diesel fuel because of its high particulate matter content, there is something to be said for the stuff.

So it is with great pleasure that I call your attention to this blog entry from the Los Angeles Times hawking the wonders of the new generation of diesels with which the Europeans will soon flood our markets.

While it notes that recent surges in diesel prices make it a less attractive choice than it was just a year ago, it points out that Honda has a diesel in development that could reach 60 mpg! Might still make sense, even if diesel prices stay high.

Hmm, I would definitely have to ban Diet Pepsi, or fluids of any kind, if I want to compete with that next time I drive to Roanoke.