Drive Differently

First of all, when I created the categories for this weblog, I had intended to use "Tech Tips" for computer-related advice (something I still have yet to get around to). In the face of rising gas prices however, I have decided to break this category in with some automotive advice.

With 10-15% of our (already taxed) oil-making capacity here in the States knocked out by Katrina, gas prices are on the rise due to the rules of supply and demand.  While we do have about 20 oil tankers steaming our way from other countries and even more oil freed up from strategic oil reserves (half from the U.S.) to help alleviate the loss, we can’t otherwise modify the supply aspect of supply and demand.  The demand aspect, however, we have full control over.

I’ll start with the obvious: drive less.  If you know you have to go to the grocery store, the band, and the post office this week, do it all in one trip, and plan your route so that you drive the least number of miles.  If you live near people you work with (and they don’t have severe personal hygiene problems), carpool.  If you live in a city, use public transportation when available.  A car may get 3 times better gas mileage than a bus, but said bus carrying 20 people gets more than 6 times better gas mileage than 20 cars.

The main object of this entry is for when you are driving your car.  It may not be obvious to everyone that how you drive your car can greatly influence your mileage.  I drive a 4,400 lb. behemoth with a 4.6 liter V8 engine.  Of course I bought it back when gas was little more than $1/gallon, but that is beside the point.  When I first had the car it had 32,000 miles on it and I averaged 20 miles to the gallon.  One would expect that this number would only decrease as the car aged and its engine became less efficient.  My car now has 112,000 miles on it and I regularly get 24 miles to the gallon.  No, my car has not gotten magically newer over time, nor have I replaced the thirsty V8 for a six-cylinder.  I simply drive differently than I did seven years ago.  Assuming I drive 800 miles a month, I am saving over six gallons a month compared to when I first bought the car!  Regular unleaded was $3.14 this morning when I drove home.  At this price, saving six gallons a month would save over $225 a year.  Not too shabby.  Just imagine what that savings would be if gas prices continued up to $5 a gallon or more.  So just how did I squeeze another 4 miles to the gallon out of my land yacht?

It started when my girlfriend bought her VW Passat.  I now dislike the car as a whole, but it does have one very useful feature: a mileage indicator.  The car can tell you what your real-time mileage is as well as your rolling average.  I became very interested in when and where a car uses the most gas.  As you can imagine, this is when you accelerate.  And the faster you accelerate, the more petro your car swills.  The second thing I noticed while driving around in the Vee-dub was that although the car averaged 30 mpg, by letting off of the gas and coasting I could max out the mileage indicator (it stops indicating at 200 mpg).  The final major thing I noticed about mileage in the Passat was that braking kills it.  It makes sense when you think about it.  If you are accelerating and then you stomp on the brakes, you’re basically wasting all the energy it took to get the car up to speed in the first place.  I translated this into a real-world scenario easily.  If you know you are coming up to a stop sign, or an off-ramp, or a sharp curve in the road, let off the gas.  You’ll find that most cars maintain most of their speed for a considerable distance.  Rather than maintain speed with the gas until you NEED to brake, let off early and coast down so you don’t have to brake as much.  When you brake, you are basically converting kinetic energy (speed) into heat energy (through friction with your brake pads).  If you keep in mind that gas is expended to make speed, the less braking you do, the less gas you waste.  Also keep in mind that while you are coasting towards a stop sign or whatever, you are most likely getting in excess of 100 mpg (remember the 4-cylinder Passat gets over 200 while coasting).

Now, before you go out and try this for yourself, I’m going to warn you: letting off the gas early just plain feels weird.  Your mind thinks that the car shouldn’t be slowing down yet, your body feels the subtle deceleration, and it feels wrong at first.  It’s funny though, as you approach the stop sign (or whatever), a switch occurs and now your mind feels like the car isn’t slowing down fast enough.  For those of you at home, this is when you start to apply the brakes.  It may take a while to feel out when the best time to let off is.  You obviously don’t want to coast all the way down to 0 mph (you’d never make it).  I shoot for ~25mph heading into stop signs/lights.  In other words, I try to work it so that I am doing 25 mph when it comes time to brake.  To help with this, I use landmarks.  If I’m doing 60 mph when I let off the gas at the exit sign, I cruise down to 25 mph at the point where I start braking for the stop light.  In the event that you happen to slow down too much, you can always apply the gas a little bit later.  It’s when you don’t slow down enough, the extra braking robs you of your mileage.  That reminds me, this particular driving method saves on brake wear, too!

In summary, to save considerable amounts of petro keep the following three things in mind:

1. Minimize driving time by consolidating trips, carpooling, and using public transportation.
2. Accelerate modestly.  Laying down on the gas on the on-ramp uses gas at a ferocious rate.
3. Anticipate stops and curves by letting off the gas early.

The less gas we use, the less demand for it there will be, and in the long run, the lower gas prices will be.  Of course when gas prices fall, people buy big SUVs, drive fast, and in general, defeat the purpose, but maybe the day that all that changes is now.  Gas prices in the U.S. are higher than ever (even accounting for inflation), and the supply of oil is not limitless.  There are exciting new technologies that will help us take off our oil ball-and-chain, but that is for another entry.  Until then, I hope my driving insights are helpful…