Winter Fuel Econcomy

[SydneyRoo]

Originally Posted by jdetzel

According to here:
http://1010tires.com/tiresizecalcula...?action=submit
There would be about a 6% increase with the smaller tires.

In other words if you traveled 100 miles your odometer would actually show 106 miles.

It actually says 5.833%, which @ 30mpg would show as a 1.7mpg increase.

That is just what that site says, I do not actually know how to do any of the tire size calculations.

Oops I goofed. The factory Michelin PS3s are 235/40/18.
I reran the calc and it said the 16s would now read 2.1% fast. That's pretty negligible IMO (ie, actual speed is 100 km/h but speedo reads 102).

The 18s are way too fat for this car, but they are awesome. My fuel eco definitely is better with the skinnier winter tires on (while it's still not actually winter yet, most days are above freezing still). Maybe when the 18s wear out I might pick up some factory 17s, just to have a hope at actually getting 40 mpg for once :p

[jsr72]

Originally Posted by GoShockers

Also, how much of an impact on fuel mileage does cold air cause? Let's take away the fuel aspect and perhaps even the warm-up period. Does the colder, denser, "heavier" air cause enough problems aerodynamically to make a difference?

To produce an identical level of aerodynamic form drag, if the air density is increased then the velocity must correspondingly decrease.

In highly idealized situation if the air pressure happens to be the same at two different temperatures, then the new velocity is simply the original velocity times the square root of the new temperature divided by the square root of the original temperature. (Use absolute temperatures in the calculation)

For instance, if a vehicle is traveling 70 mph at 70F, then it experiences the same amount of form drag at 67.3 mph at 30F.

[MelloYelloTi]

Last 2 tanks have averaged to about 27 to 28 mpg overall. Down about 4 mpg from about a month ago. Still not to bad as my Sable was getting 16 to 17 mpg overall in the same temps..

[gkirk]

Originally Posted by jsr72

To produce an identical level of aerodynamic form drag, if the air density is increased then the velocity must correspondingly decrease.

In highly idealized situation if the air pressure happens to be the same at two different temperatures, then the new velocity is simply the original velocity times the square root of the new temperature divided by the square root of the original temperature. (Use absolute temperatures in the calculation)

For instance, if a vehicle is traveling 70 mph at 70F, then it experiences the same amount of form drag at 67.3 mph at 30F.

I think the ideal case is pretty good - without putting the car in a wind tunnel and checking it.

:)

[Pinion Dominion]

Today I drove my usual 4.1km to work. The temperature outside was -19 degrees Celsius.

When I started my car the distance to empty was 401km. When I got to work the distance to empty was 380km! (When I fill up to max, distance to empty is 540km)

Now I always found the distance to empty was a pretty accurate number as it seemed to be tailored for city driving. For example, when I drive 120km (90% highway) to visit family, the distance to empty goes down at max 80km.

Is there any tips you guys have to improve winter fuel economy?