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Driving Efficiently (Hypermiling?!)

Q: Does accelerating and coasting give better fuel economy than just constant cruising?

A: Don’t answer that question.

  1. What speeds are you operating between and acceleration rate do you use to increase your speed?
  2. What car are you driving, is it manual or automatic, and what is the speed limit (i.e. what constant speed would you otherwise be cruising at)?
  3. Is it a hybrid, does it have direct injection, or anything else that might make it more efficient than the “average” car?

The best general advice I have, for those of you who have no problem driving like a wacko, is to accelerate slowly, coast for a long time, and drive at or even below the speed limit! Just please don’t drive in front of me.

The one equation I will give is F = aV^2 + bV + c. The total drag force opposing your car looks pretty much like a speed quadratic equation. The lower your average speed is, the better. Right?

There are TWO factors in fuel economy.

  1. The net required energy at the wheels. This is due to the drag force, inclines, and possibly regenerative braking if you have a hybrid. 2. The efficiency from the fuel tank (or battery) to the wheels. This is due to fuel losses, heat losses in the engine and transmission, and extra loads like air conditioning and sub-woofers.

The best answer for those who are still reading is to hook your Android smart phone up to your vehicle’s information network (CAN) through the handy OBD-II port under your dash. I found a free Garmin app and for $90 I bought a wireless OBD-II to Bluetooth transmitter so I can read and record live data, AND check codes!



Maybe it does, but you’re making the people behind you really angry at the constant speed changes, and that’s a BAD thing.
If one is truly worried about fuel economy, you’ll park the car and ride a bike instead.
I, however, am not, and it was very funny to see the reaction of the salespeople I said that to when I was shopping for my new car.

I think that accelerating slowly is one of the most over-rated gas mileage techniques there is, indeed, it has even been shown that you can lower your gas mileage by accelerating too slowly.
I have personally gotten some of my very best gas mileage numbers by accelerating surprisingly briskly.

Here’s the deal.
Everybody knows that aggressive drivers get bad gas mileage, no controversy.
Everybody knows that aggressive drivers do “jack rabbit starts”.
Conclusion: Jack rabbit starts cause bad gas mileage.
Wait a minute, not so fast!
Jack rabbit starts are not the only thing an aggressive driver does. Follow an aggressive driver down the highway and you will notice that he uses the brakes…a lot.
He changes lanes and accelerates only to brake back down to his previous speed and then 10 or 15 seconds later he does it again, and again, and again.
Aggressive drivers get bad gas mileage because they accelerate a lot, not because they accelerate wrong.

Some years ago BMW did a test to find out the optimum acceleration rate for best gas mileage, according to them,‘brisk’ acceleration combined with early upshifts worked best (in a BMW anyway)

I’ve averaged the same MPG whether I drive quickly or trying to save gas; summer or winter