First Tank of Gas!!!

<div class='quotetop'>QUOTE(jpmorgan49 @ Oct 2 2007, 08:29 AM) [snapback]520245[/snapback]</div>

Congrats on the new car! I'm still on my first tank of gas from the dealer on my second Prius (the 2004 died in a crash so that I didn't) and am getting 46.6mpg after the first 100 miles off the dealer's lot and I haven't gotten around to increasing the tire pressure yet.

On my old one, I ran at 40/38 and had a perfectly fine ride and didn't notice it being any rougher than at the 35 or 33 or whatever the dealer usually sets it to.


Aren't these cars great? I never really cared about my tire pressure (except to make sure that I wasn't running flat/too soft) before getting my Prius and now this car has turned me into a quasi-gearhead.

 

Where's the back-up beep information?

 

<div class='quotetop'>QUOTE(skguh @ Oct 3 2007, 06:47 AM) [snapback]520546[/snapback]</div>

http://priuschat.com/Disabling-the-Reverse-Beep-t38494.html

 

<div class='quotetop'>QUOTE(jpmorgan49 @ Oct 2 2007, 08:29 AM) [snapback]520245[/snapback]</div>

I wouldn't say 44/42 is the norm. There's been a poll on that, but they didn't include an option for people who never checked the pressure or didn't know, which I think would be an interesting stat, and I think it started at 35/33. I run about 39/37 myself, splitting the difference between the tire rating and Toyota's recommended vehicle rating. Some people are adamant that 35/33 is the highest "safe" setting, although I'm sure that's a compromise between ride, handling and mpg (dealers tend to lean toward ride and lower the pressure, sometimes to unsafe levels). Needless to say, there's been whole threads on that. Bottom line is work your way up to something you're comfortable with. May depend on how you take corners, if you brake hard, and how bumpy your roads are. I'm sure you also know that tires lose pressure when the temperature drops, and always recheck your tires after they've been rotated - dealers have been known to move them front to back and not change pressure, so now the higher-pressure tires are in back. At best they'll drop them back to 35/33.

Edit:
Here's the poll: http://priuschat.com/index.php?showtopic=33498&hl=
I was wrong, there was an option for don't know, however the pressures started at 38/36, and didn't even include the default 35/33.

 

:compromise between ride, handling and mpg (dealers tend to lean toward ride and lower the pressure, sometimes to unsafe levels).

I have alot of dental work, what with crowns and bridges and such. I've always heard that the tires, when fully warmed, got the best total performance at their recommended pressure (i.e., handling, ride, safety, fuel, etc.) and that meshes nicely with my coincidental acute awareness of road surfaces via my teeth.


But seriously, folks, what is the perceived "BEST" tire pressure?

 

<div class='quotetop'>QUOTE(skguh @ Oct 3 2007, 01:09 PM) [snapback]520716[/snapback]</div>

skguh,

42 front/40 rear is pretty popular on this thread. I personally run 39 front/37 rear and have found that to be a good compromise between economy and comfort.

 

<div class='quotetop'>QUOTE(Sliderule @ Oct 3 2007, 01:59 PM) [snapback]520751[/snapback]</div>

Is there any comparison in the different mileages? For instance, AT recommended pressure, MPG = 47 whereas at 2.5 psi above, MPG = 50 or something? Is there a metric?

 

<div class='quotetop'>QUOTE(skguh @ Oct 3 2007, 02:05 PM) [snapback]520756[/snapback]</div>

You would think there would be, and general test reports say that more PSI raises MPG. There's a bunch of anecdotal evidence here on PriusChat backing that up, maybe a search in the Fuel Economy forum would be helpful. But I couldn't quickly find a chart showing that. One of the problems is that there are so many variables and while tire pressure makes a difference, driving conditions, air temperature, engine temperature etc. make a difference, and in the short term that difference can mask any difference caused by change in PSI, so the tests have to be done very carefully and probably over longer runs.

From http://www.fueleconomy.gov/feg/maintain.shtml:
"Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer."

I'm not sure that would be linear. I think the difference would be greater for low PSI (going from 20 to 25 psi) than for higher numbers (40 to 45). Some people claim higher improvements than that, perhaps double. Might depend on the type of tire and car.