Scan Gauge and MPG

Saturday March 15th 2008 I bought a Scan Gauge II and began an unhealthy obsession with gas milage.

I had been considering the device for many months, but was a little put off by the price. After a bonus check from work, I decided it was time. While I was driving around doing some errands, I called Linear Logic, which is right down the road from me in Mesa, AZ. Though they were closed on Saturday, Ron, the owner was there, and offered to hang out to sell me one.

I zoomed over, and Ron sat me down in their conference room while he filled out the order sheet. We talked for about 30 minutes about hypermiling and getting crazy milage out of his Prius. This is clearly a guy who loves what he does.

Setup The device requires a little set-up and calibration, that while no big deal for the average geek, would make anyone not technically inclined pretty crazy. The device itself is clearly designed by an engineer. While it’s highly functional, it’s pretty obtuse in navigation of its features. Your mom can use it, but she can’t install it and set it up.

Two measurements that you’re immediately interested in are instant MPG and current trip average MPG. the first is a predefined gauge, and the second requires a little setup. Once done however, those two readings will change how you drive, even if you don’t want to go crazy trying to hypermile.

Driving If you’ve read that Wikipedia article, you’ll have noted that relatively large gains in average MPG are attainable through some pretty simple changes in driving habits. Unfortunately without having instantaneous feedback it’s hard to tell what works and what doesn’t.

While it’s nice that congress has passed laws demanding cars that are more efficient, they could have a much larger impact passing laws that demand realtime MPG readouts on all cars. Seeing yourself get 7 MPG makes you change your habits quickly.

I wanted to show you some cool numbers for demonstrating how much I’ve improved my milage, but after the first year of owning my car, I just stopped caring. Now that gas is above $3 and doesn’t look like it’s going down again any time soon, I started to care again. I’d guess I was averaging 34MPG.

My last tank averaged 39MPG with a mix of city and highway driving. On my current tank with trips over 15 miles I have consistently averaged over 50MPG. Most of the gains can be attributed to “Pulse and Glide” driving where you bring the car up to speed, then take it out of gear and coast. Some people turn the engine off while doing this, which can make a big difference, but I’m unwilling to loose power brakes and steering.

Short trips on a cold engine will nuke your over-all average though. It’s really hard to get a cold engine to give up the MPG.

There are a couple of big things that kill efficiency on “economy” cars. Aerodynamics, and idling engines. All modern cars should turn off the engine when the car is at a stop, and restart automatically when needed like hybrids. I suspect this alone would save a ton of gas and pollution. Aerodynamics is probably more difficult, as aerodynamic cars tend to be pretty ugly.

Overall, the scangauge is a worthwhile purchase. One things of note though: When temperatures rise, the LCD goes dead black. This was really surprising considering this is from a company based in Mesa.

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