I drive a '92 Buick Skylark, 2-door, w/ a 2.3L 4 Cylinder 120 hp engine 3 Speed Automatic Transmission, A/C broke long ago.
Occasionally, I find cause to take a road trip and keep track of my fuel efficiency and average speed along the way. I recently set a new personal record of 383 miles on a single tank of gas (~14.2 gallons), averaging ~27 mpg at nearly 75 mph.
Over the years, I have noticed a trend contrary to the popular opinion that slowing down increases fuel efficiency. I find that the faster I drive, the more fuel efficient my car becomes. It seems to me that my car is most efficient at speeds well in excess of 80 mph. Could this really be true, or am I discounting certain variables?
Here's my recent experience - rental '08 Maxima, Kansas City to Topeka at 70 mph, got 27.5 MPG, Topeka to Kansas City at 75 MPG got 26.0 MPG. I would expect the general rule "faster = lower MPG" to hold true, with exceptions for a minority of cars, certainly above 60 MPH.
The Buick Skylark may have been designed to get its best gas mileage at 75 MPH, like other cars.
ok, so a car can be designed to be most efficient at a given speed. how do they decide what that speed should be? from the driver's standpoint, it should, ideally, be optimized for their normal daily driving speed. is it possible to design a car to have 2 optimum speeds, allowing a driver to select a 'city' or 'highway' setting? if all cars are different in this way, maybe they should be more open about it and even provide different setups so people can buy for city or highway driving. little difference for each car, sure, but a lot of savings with millions of cars.
Make no mistake; MOST cars, your Skylark included do substantially better at <55mph than 75+. CR tested a Camry, at various speeds and a general trend of 5 mpg loss was found for 10 mph increase between 55 and 75 mph. You're still trying to change the world as we know it. Milage figures for Corvettes also show better fuel efficiency at lower speeds...55 vs 80 mph.
The Buick Skylark may have been designed to get its best gas mileage at 75 MPH
Please tell me how a car gets LESS wind resistance at 75 then it does at 55!!
A car's ENGINE may be most efficient at a certain RPM...and in a high gear that may very well be 75.....HOWEVER....Even with the engine at peak efficiency I do NOT believe it can overcome a 40% increase in wind resistance at 75 compared to doing 55. Engine efficiency is only ONE factor in determining maximum overall efficiency. And Wind resistance is by far the MOST important factor.
We're not talking about a 4 cyl. race car, where these arguements "could" have some legitimacy. We're talking about "mall car" with a three speed auto. Any increase in milage as discribed would require a suspension of reality and physics, which I fear we are engaged in. A push rod 4 cyl. Skylark by it's nature is incapable of reality revision.
07/24/2008 5:09:32 PM
