Now I think I know why my mpg has been so good

I'm running same pressures because it expedites my DIY tire rotations, the front/rear differences are trivial, and it just keeps it simple.

The Prius has the not insignificant weight of the hybrid battery in the back. Not sure what the ratio is; is it published? All our previous Hondas had significant front bias, but the same tire pressure spec all around.

Here's something:

Weight distribution front and back | PriusChat

Our previous Civic Hybrid had published 59/41 (front/rear) ratio, and tire pressures the same all around. I think Toyota's on to something, it's sensible to put higher pressure in the more heavily loaded front end, but I the difference seems trivial, especially if you've got all the tires a bit higher than spec to begin with.

 

Bicycle tires rated at 100psi or over generally have a cross section of less than 2 sq inches which mean the the circumferential force generated by the air pressure would be less than 200 lbf.

Car tires are likely to have a cross section more than 30 sq inches which would correspond to a circumferential force greater than 3000 lbf at 100 psi and greater than 1200 lbf at 40 psi.

Car tires are of course rated for much heavier loads and are constructed accordingly.

 

When I was a "tire buster" in my youth, we would have to inflate tires to over 100 PSI to "set the bead" upon new tire installation. Never an issue in years of practice. The only negative incident I ever witnesses was with a tire with a defective bead that burst with explosive force. Picked me up off the ground a through me several feet backward. But, like I said. The tire was defective.

 

Yep. Most likely you teeth will hurt or you will hit a pot hole. Drove with 90 for two weeks before I took it to the dealer and ask what up.

My 2011 had 26 psi cold when it was delivered

 

I agree with keep it simple. I will run the same pressure in all 4 tires. "40" is my magic number.
I'm a big heavy guy, with my seat all the way back... it's almost like sitting in the middle of the car.
And I occasionally carry heavy items in the trunk.

I joke about how noisy my OEM Toyo tires seem to be. (It all depends on the road surface... Not a big deal anymore.) But I'm very happy with how smooth they ride, and the handling and cornering is just fine for my conservative driving style. I'm certainly enjoying a very consistent 60 MPG! When they eventually wear out, I would even consider buying the same tire again.,

 

But modern steel belted radial tires on normal passenger cars are vastly less susceptible to this than were old fashioned bias ply tires.

Those steel belts under the tread don't expand much under pressure, so the tire center doesn't bulge out the same way it did with previous tire construction methods.

 

That's good. Too, I suspect extreme tire pressures are tough on suspension components.

@Danny this took about 4 tries to post, about 30 seconds of stall with each attempt.

 

4 months with my new Prius. I maintain a steady average of 60 mpg, in routine stop & go city driving and short freeway (highway) trips.

This car is too good. I'm bored already.

Now I'm curious as to what would be the worst city gas mileage I would get? I am currently conducting that experiment with my latest full tank. I will drive my Prius like a regular car, in "Normal" mode, (and more often in Power mode) paying no attention to any Eco fuel-saving measures. I will drive like all the other nuts out there... exceeding the speed limit, bolting off the line from light to light, and zipping in & out of traffic.

So far, after about 80 miles of being crazy, the MPG hasn't gone below 56.

 

That's a solid 20% increase over our 3rd gen lifetime average, which translates to something like 48 mpg US. We're duffers, try, but not rabid. Also, have 17" Michelin PIlots. Only caveat, I'm guessing that 60 mpg is displayed, but still at least 15% increase.

I think it's mainly down to the much more aggressive use of the battery, hopefully they didn't push it too far.

 

Hi Mendel. My average of 60 mpg, (six fuel-ups) was always hand calculated. I don't rely on the computer display. The lowest I calculated, was 59.2. And the best was 60.7, if I recall. (I usually fuel up when the gas gauge reaches the last bar... somewhere around 530 miles driven. Just FYI.)

Now I gotta see how bad I can get those MPGs. I'm very curious to see the worst case scenario; for city driving, that is.

 

EDIT:

Oops, we cross-posted and you answered my question.

Is that what is displayed on the lie-o-meter, or hand calculated from the pump and odometer? My gen 3 fairly consistently reports about 3% optimistic for the MPG.

Regardless, very impressive numbers for the Gen IV, especially since the EPA rating didn't appear to be much better than the Gen III. Seems the real world results are more favorable to the new Prius.

 

I use my trusty iPhone calculator.

Now, I'm driving it like I stole it... And with the AC always on. And I bet I still get no lower than 50 mpg.

Darn... this Prius is just no fun!

 

78% nitrogen is free.
~100% nitrogen is mainly a technique used by tire shops to extract surplus dollars from rich suckers.

 

Like the OP when I bought my new Prius, I found that the tires were inflated way above the recommended PSI.
I don't know who did it....the dock, port, or dealership.
When I took actually took possession of my Prius it was really brand new, with less than 20 miles on it, so whomever inflated the tires to that level surely didn't do it to drive it. It was less than 20 miles including a modest test drive.

Somebody told me once that the ports will inflate tires beyond the norm, to help protect the tires, rims, over what might be long periods of standing still while being transported.

Do not know if that is true.

 

The factory did it, at least if you found 40-ish on your Gen3.

The dealership was supposed to lower it to the door label numbers as part of dealer prep. Mine didn't, and that saved me most of the work (on a hand powered bicycle pump) of pumping them back up to the pressure I want.

 

That's why we are not getting center wear. Great post.