alignment and tires mpg

[98outbackpdx]

i got a alignment and 4 new hankook tires for my outback so i could drive to California (safer, the old tires were dangerous.)
my mpg went from around 20mpg to 25 mpg.
i went from (on my way back) the southern point of Ashland Oregon to the Wood Village Safeway (Gresham/Troutdale area) on one (1) tank, over 300 miles, with stopping 5 times for this and that, and driving at 75-80 mph and driving through the southern oregon mountain range, that tank i got 24.5 mpg.
can an alignment and tires boost the fuel economy that much?
very happy with the hankooks, they have quieted down the car considerably.

[tecnica technician]

yeah if the tires were pretty shot like to the wear bars or more and you had a really bad alignment with like bad toe, caster, or camber all around it could definitely effect your mpg, keeping your tires inflated to the right psi can also cut it down.

[98outbackpdx]

the tires were at 35 psi well above the subaru specs. and the tires were about half way worn down, but when it was wet the tires lost almost all traction.

[ouch1011]

Absolutely tires and alignment can affect your fuel economy.

With tires, its all about rolling resistance. High performance tires will have a higher rolling resistance than all season tires because the tire rubber compound is softer/more sticky. They grip the road better, which meakes them harder to spin. All seasons don't grip the road as well and usually have a harder tread compound, so they roll more easily. Super cheap or some "touring" tires with super soft sidewalls for a better ride quality have a higher rolling resistance because the sidewall flex uses some of the energy (converts it to heat). Same idea as if you have low tire pressure. Low rolling resistance tires (like some fanatics use on their hybrid/electric cars) use super hard tread compounds and super hard sidewalls to make them roll like stones...they roll really easily, but at a severe cost of ride quality and noise. Tire width can even affect aerodynamics, wider tires are less aerodynamic. Some higher performance cars will actually have air deflectors to direct air around the tires to improve aerodynamics.

Alignment, mainly toe is going to affect your efficiency. If the tires are not correctly aligned, you'll be effectively dragging them down the road, which can drastically increase your tire wear and decrease your fuel economy.

Did you get the same size tires?

[TheSiege]

I'm getting an alignment as I post this, the numbers on this spec sheet are overwhelming. I wish I could change my camber and crap on my coilovers without royally screwing everything up... But it will be interesting to see what happens with my mpg because my numbers are SO asymmetrical with bad toe and I've been getting 30 on avg with the 2.5

[98outbackpdx]

yes i got the same tire size, P205/70/15 stock tire size for the outback my generation. i went form kumho solus kr21 (old tires) to hankook optimo h727 (new ones.)

[Sarra]

Go under your car and intentionally screw your toe up, front and rear. Not only will your car handle like crap and you will destroy your tires, but you will get like -5 MPG.

I saw an increase from 22 MPG to 30 MPG on my WRX just by fixing the toe problems my car had. Now I gotta fix the camber in the rear.

[anothernord]

The tread pattern also affects MPG. An aggressive tread on a tire, like winter tires, have way more rolling resistance than all-seasons.