Christofoo Review

(Updated 3/23/12 for clarity, added minor points.)

Different people care (or don't care) about gas mileage for different reasons:

• Gas prices
• Global warming
• National security (for example our armies require oil, the economy requires oil, also some of the money we pay for oil is likely to end up in the hands of a few of our national enemies)
• The politics of oil (for example if you think the Iraq war was in fact blood for oil, also see Africa)
• Smog emission
• Oil drilling and other environmental impacts

Personally I'm not really sensitive to cost, and smog emission is not strictly related to gas mileage, but the other factors concern me. That being said, the average American stands to save around $200 per year for every 10% they improve their efficiency.

Congress has the most power to address oil issues. After all, what good does it do for me to get 45 MPG in my Toyota if everyone else on my block is getting 7 MPG driving their Hummers all around the country? The most important thing you can do for gas mileage is to write your congressmen. (Thank you congress 2007!) Nevertheless, this article is about me doing my little part with the car I already have.

You probably already know that your total gas consumption depends on:

1. the number of miles you drive,
2. your vehicle of choice,
3. other details

Today I want to focus on the "other details," to show how you can reduce your gas consumption by 10-40% without changing anything major. After all, the number of miles you drive adds value to your life (or do they??) and changing your vehicle means buying one (unless you have a high mileage sedan sitting unused in your garage), and buying a new vehicle has its own set of environmental and economic consequences, which may or may not fit your circumstances.

"Hypermiling," means a set of practices which achieve better gas mileage than the EPA has rated your car for. There is a world of gas-saving tips - I would say "hypermiling" is a particular brand, coined at cleanmpg.com - and this is the philosophy that I subscribe to. Hypermiling aims to be safe and legal first and foremost. Here is my (hopefully quick) summary of things you can do:

1. Get a gauge and a compressor or electric pump, and check your tire pressure once a month or seasonally. (Of course you can do this at a gas station, if that isn't an inconvenience to you.)
2. Also, increase your tire pressure. Check the maximum rating on the sidewall of your tire, it is probably either 44 or 35 PSI, even if your vehicle manufacturer recommends only 30 PSI. Some hypermilers pressurize their tires up to 60 PSI, I've done most of my hypermiling at 44 PSI, but have recently decided to try 50 PSI. (Read more about tire pressure.)
3. Switch your engine off when stopped at lights (if the wait will be longer than about 5-10 seconds). Note that you can run your battery down by doing this, especially at night while your headlights are on. I own a battery charger, and probably charge seasonally or sometimes monthly. Aggressive hypermiling in heavy stop-and-go might justify owning an on-board trickle charger so you can easily charge a few hours after every time you drive. I feel personally convinced that this practice really isn't too hard on the starter or the engine, as long as you are careful not to start the engine while it's still running. The starter doesn't get very warm during a quick start (unless there is too much coughing - a sign of engine trouble), and the oil is still coating the engine after a few minutes (take out your dispstick and see how long it takes for the oil to run off and leave the metal bare - it won't happen while you're stopped at a light).
4. Change the way you drive to reduce the amount of braking that you do. Pressing the accelerator is like making an investment in kinetic energy, and whenever you press the brake you take a loss. When you see a pedestrian moving towards a crosswalk half a block away, or if you see a green light that might turn yellow, then kinetic engergy might be risky right now. And certainly when you see a red light a block ahead, that's the wrong time to invest. This doesn't have to cost you any time, you have to wait at red lights anyways, and leaving space in front of you and planning ahead makes you a safer driver. (Okay, once in a while I miss a light that I could have made, but it's rare and it just isn't important to me.) However, I don't slow down too much when approaching off-ramps if it's going to cause congestion on the freeway behind me, and I don't glide through intersections without stopping. Use common sense.
5. Speed: Above around 55 mph, air drag dominates and reduces mileage with increasing speed. Below 55 mph, the problem is that conventional gas engines are like leaky buckets, and the longer it takes you to get somewhere, the more it will spill. So on surface streets, the speed limit is best, as long as you can plan your stops and keep off the brakes. At freeway speeds, it pays to drive the speed limit or lower if traffic permits. On long road trips, it can be difficult to weigh gas mileage versus trip time. I find myself unwilling to spend an extra hour in the car on an all day trip to save two gallons of fuel when I have fussy kids in the back (but when I'm driving by myself I might).
6. AC hurts mileage. My trips around town are mostly under twenty minutes, and I can generally brave the heat, starting with the windows open with the fan on. When I get up to freeway speed I close the windows and leave the fan on. Sunblocks are a must. (Okay, actually I run the air conditioner when I have kids in the back. Pulling a sad child from a sweaty, sticky car seat isn't worth it.)
7. Automatics benefit from gentle acceleration. Manuals (and manumatics) benefit from shifting early to keep the RPM around 2000 (give or take).
8. Advanced: The engine acts as a brake when you take your foot off the gas. Broadly, this means you need to control your need to decelerate. Give yourself a buffer and don't use the engine as a brake. When you do need to correct your speed, or when approaching a stop, or when going downhill where the engine is not needed for power (and not needed for a brake!), manual transmissions and some automatics can be clutched or shifted to neutral to glide for a long distance to reach a lower stopping speed, thus making the best of your investment in kinetic energy.

For a longer discussion with even more saving tips, I'll refer you to Wayne's definitive description: http://www.cleanmpg.com/forums/showthread.php?s=f5c361d9598538b8109aa99f...

Currently I'm getting these figures in mixed travel (my "in-town" commute is about 70% freeway and 30% city):

• 40-50 MPG with a 97 Civic (30-40 MPG before hypermiling = 20-30% improvement)
• 38-45 MPG with a 89 Corolla (28-35 MPG before hypermiling = 20-30% improvement)

Before hypermiling my driving habits were between "normal" and "conservative", so your gains may be a higher percentage if your starting point is "aggressive". Also some vehicles may benefit more than others due to driving habbits, but this is more complicated to discuss.