Vue Fuel Economy with Tires at 35 psi

Discussion in 'Saturn VUE' started by C. E. White, Nov 2, 2005.

  1. C. E. White

    C. E. White Guest

    Well courtesy of GM, I have conducted a simple experiment on of the effect
    of tire pressures on gas mileage, at least for one vehicle and one set of
    tires. My Vue, when delivered, had a recommended tire pressure of 30 mpg all
    around (which I maintained). After the vehicle flunked the NHTSA extreme
    maneuver rollover test, GM revised the rear suspension and upped the
    recommended tire pressure to 35 psi. For the 7000 miles before the change,
    the car averaged 22.1 mph. For the 7000 miles after the recall (and the
    change to 35 psi), the mileage was 22.9 mpg. I was surprised at the
    difference. In fact, before the tire pressures were revised I never had a
    7000 mile segment where the average fuel mileage was over 22.4 mpg. (low for
    a 7000 mile segement was 20.9, high 22.4) So, it seems to me that inflating
    the tires an extra 5 psi increased the fuel economy by 0.3 mpg to 0.8 mpg.
    I would have thought if this was typical, GM would have specified this
    pressure from the beginning. On the other hand, the car is now much more
    nervous when driving. It reacts to subtle changes in the road, and reacts
    quickly to minor steering inputs. The ride is not much different, and in
    fact, after a few months, I can't tell any difference in the ride quality. I
    just replaced the original Bridgestone tires with Michelin LX4's, so it will
    be interesting to see what happens to the fuel mileage now. Of course the
    difference in fuel mileage might be related to other changes, but I don't
    think I made any significant changes in my driving pattern recently,
    especially since the variance between other 7000 mile segamens was around
    +/- 0.25 mpg (21.15 +/- 0.25 mpg).


    Ed White
    C. E. White, Nov 2, 2005
  2. C. E. White

    Bob Shuman Guest

    What you observed correlates with the fact that there is less surface
    contact area and a lower rolling friction. If you really want to see a
    difference, try running the same experiment with the same percentage of
    reduced pressure (simulating people who do not inflate their tires come cold
    winter months).

    Bob Shuman, Nov 2, 2005
  3. C. E. White

    blah blah Guest

    My tires are rated at 44psi and I inflate them to 44. I drive a
    bonneville and at 75mph on the highway (70ish average time over long
    distances) and I get 27.8-28mpg. Its rated 28mpg on the highway by the
    EPA and they average 48-49mph or so on a treadmill. Never tried running
    them with less air but I'm sure they would have a negative effect if
    lowered to the cars specs.
    blah blah, Nov 2, 2005
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