Tire pressure and mileage

[Sheldon]

Hi,
Also check the pressure when tire is cold. I fill my tires with Nitrogen
gas from Costco tire shop. Nitrogen is more stable. If pressure is too low
or high yo'll know it when you drive.

No nitrogen, but always check pressures when cold and the sun isn't heating
up one side of the car.

 

[Sheldon]

My Subaru dealer was filling tires on all new cars with nitrogen and
adding $200 to the total cost. After one year they discontinued this.
I was told they found it added negligible benefits, unlike when it is
used in race cars, so they will use up their nitrogen supply during
repairs only.

I suspect they stopped because they were getting too many complaints
about the added cost.

BoB- Hide quoted text -

- Show quoted text -

Even our county police have been running nitrogen for highway patrol.
May give you some benefit but probably not worth the cost. Now,
helium is the way to go if you really want to reduce unsprung weight.

Seriously, pumping your tires up will not only improve mileage, but
handling as well. When I used to autocross a Corvair I'd run 50 psi
rear and 30 psi front, with much wider tires on the rear as well due
to the extreme weight imbalance. For a street Subaru 35 psi, or
whatever the tire manufacturer's maximum is, should optimize gas
mileage, tire life and handling. And check that air filter. I belive
the Subaru interval is usually 20,000 miles, but If you've got more
than 10,000 and it's underperforming, it's a good place to start with
a small investment.

 

[Sheldon]

Hi,

Yes, it does.

From personal experience, I've found different tires produce quite
different mileage characteristics depending on pressures. Some are
pretty "pressure tolerant" meaning mileage won't suffer much when one
drops a couple of pounds or more. Others REALLY start to show the
difference. (Same issues w/ handling!) As many have suggested, I, too,
run 1-3 lbs over the door sticker w/ most of my tires.

I check them about every two weeks, and keep 'em filled w/ a 78%
nitrogen mixture. It cost me $200 for a pretty good compressor set up to
use that mix... but you can get one for considerably less.

Get a good gauge, too. Some like digitals. I've got a nice one and it's
ok, but I prefer the real Accu-Gauge analogs (there are plenty of cheap
knock-offs but I'd avoid 'em.) Pretty bullet-proof and they never need a
battery. Get the style w/ the built in "bleeder" and you can adjust down
to 1/4 lb increments on the large dial models if you wish (my digital's
only good to 1/2 lb.) Local availability is spotty, so you may want to
go online. I think the name of the place where I ordered my last ones
was called "getagauge.com" or something really close--Google's your
friend.

Pencil gauges aren't on my radar screen anymore: we used to get really
good ones when I worked in service stations back in the
late-'60s/early-'70s, but everything I've seen recently is cheapo,
cheapo and not all that accurate.

Rick

I have a really good German dial gauge that adjusts for atmospheric
pressure.

 

[Sheldon]

I was taught that diffusion rates are normally inversely molecular
weight dependent and with N2 at 14 and O2 at 16, the N2 tire should
deflate faster. I suspect it doesn't because of osmotic pressure - the
pressure of O2 trying to get in to dilute the N2.

ROTFLMAO :-D