Most efficient speed?
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AudiWorld Senior Member
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Most efficient speed?
I have noticed that my 97 A6 Quattro Auto seems to get the best MPG around 72-75mph. I thought most cars were suppose to get the best MPG around 55.
What have you folks noticed/know?
What have you folks noticed/know?
AudiWorld Super User
Joined: Jun 2003
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I don't think it's speed as much as it is aerodynamics and torgue.
Every car is probably going to be more efficient at different speeds.
For example, in the 70-75mph range, my Suburban is running beautifully. But because I'm pushing the aerodynamics of 2 sheets of plywood down the highway, I'm getting 11mpg. If I bring the speed down to 60-65mph, I can get closer to 18mpg.
For example, in the 70-75mph range, my Suburban is running beautifully. But because I'm pushing the aerodynamics of 2 sheets of plywood down the highway, I'm getting 11mpg. If I bring the speed down to 60-65mph, I can get closer to 18mpg.
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Most get best mpg around 40-55.
But that varies. German cars have different gearing and torque curves than American cars.
You want:
high gear
high speed
low rpm
low gas pedal position
On the wife's chevy, that's somewhere around 45-50mph. On my Audi, it's closer to 65.
You want:
high gear
high speed
low rpm
low gas pedal position
On the wife's chevy, that's somewhere around 45-50mph. On my Audi, it's closer to 65.
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AudiWorld Senior Member
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Are we overanalyzing this?
While each car will have a different drag coefficient, and different gearing, and different engine torque at speed etc, are they all that different when it comes to best speed/mileage?
All cars have a drag Co, whatever it is. Regardless I think we can agree that most any vehicle that is viable to drive on public roads is capable of cruising in top gear at 64kph (40mph).
Also wind drag increases with speed, so is this a low enough speed that wind drag is low, while still high enough of a speed that you are moving fast enough to be able to use top gear with low RPM/throttle use. Regardless of the vehicle.
All cars have a drag Co, whatever it is. Regardless I think we can agree that most any vehicle that is viable to drive on public roads is capable of cruising in top gear at 64kph (40mph).
Also wind drag increases with speed, so is this a low enough speed that wind drag is low, while still high enough of a speed that you are moving fast enough to be able to use top gear with low RPM/throttle use. Regardless of the vehicle.
AudiWorld Senior Member
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Drag increases as the square of velocity...
If you increase from 40 to 80 mph, the drag doesn't double, it quadruples. A better coefficient of drag will have a tremendous impact on the amount of fuel used to maintain the higher speed. So, the relative difference in fuel used at 80 mph is going to be lots more for a barn door Suburban than a svelt C4.
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