[wvargas]

Hi to all from sunny Puerto Rico.

My '04 suffered a sudden drop in mileage and more frequent intervention of the ICE after I checked and ajusted tire pressure.

I followed the recommendations about tire temperature and everything else that has been said.

When I measured the tire pressure, it clocked at 29 psi on all tires. At this point my mileage was incredibly high: close to 49. If figured that after following recommendations, I could at least maintain such a stellar performance...

The factory recommended tire pressure as printed on my Prius is 35 front / 33 rear. The recommendations I've read say that for optimum performance, tire pressure should be at 42/40. Since we are under a scorching summer with temperatures ranging from 87 to 93 degrees farenheit, I calculated that leaving it at 35/38 would be a safe middlepoint.

Wow, what a difference (on the negative side).

Inmediately after that I started to notice a change in performance that I believe lead to not achieving the 500 miles per tank mark. Since I refueled, I cannot get past the 44 mpg mark. Before, I could coast in "stealth" mode on my way back home. Now it's very difficult.

Any ideas or recommendations?

 

[Brian]

Do you mean 49 psi instead of 29 psi? Because at that low of psi, the mileage should be terrible and going up to 49 should be a big jump up in mpgs. So, do you mean you went from 49 down to 35? Because you will suffer. I keep mine at 42/40. Seems nice.

 

[wvargas]

Hi Brian.

You read right: 29 psi.

I was VERY surprised when I measured it. And by the way, it wasn't with a cheap $1 tire pressure gauge. I spent $35 on a device sold by Brookstone...

Do you think that by going all the way to 42/42 the "mystery" can be solved?

 

[richard schumacher]

Those "scorching" temps in PR would be a cool front in Dallas or Phoenix. Tire pressures are to be measured when the tire has been driven no more than one mile in the hour before the measurement. It doesn't matter how hot or cold the day is; it makes a difference only if the average daily air temperature changes by more than about 20' F., so if that happens the pressure should be re-measured and adjusted as needed.

Take your tires up to 42/40 and see what happens to your MPGs. That 29 PSI reading is suspect. At that pressure the tires would have been noticeably flabby and couldn't possibly give good MPGs. Your first result is more likely because of an inaccuracy in the gallons used or miles travelled (for example, did the odometer accidentally get re-set during that tank?).

 

[melgish]

Take your tires up to 42/40 and see what happens to your MPGs. That 29 PSI reading is suspect.

Before you do that, get a second opinion from another guage. If your guage is faulty and reading 10 PSI below what it should, inflating it to 42 (52) could cause a rupture! Double check and be safe!

 

[Brian]

I spent $35 on a device sold by Brookstone...

Good choice. I think I have the same one.
But, if it is faulty, 29 psi seems really low to be getting good gas mileage.

I got a good question....
If Toyota tested the car with 35/33 psi for their EPA estimates, then why aren't we getting closer to that with our tire's psi's at 42/40?

 

[Daniel]

Just a clarification: Toyota did not do the mileage tests. The EPA does those tests itself. I would imagine (but do not know for sure) that they use the manufacturer's recommended tire inflation.

And another clarification: The EPA tests are done under ideal and unrealistic conditions. People whose driving conditions are similar to the test do indeed get the EPA mileage, and a few individuals, lucky enough to have ideal conditions, and dedicated enough to practice extreme driving techniques, exceed those numbers.

You can read their reports on this and other chat boards if you look around. Some chat boards have a forum dedicated to mileage.

 

[Jeffand]

On my first tankfull i got 52 MPG. But I do a lot of country driving. And I drove the car easy, because the engine was still going threw the 600 mile breakin period. The second tank full looks like i will get similar milage.
Tips :idea: Don't drive over 65 mph. Also resist mashing the accerator. If you live in a hilly area your milage will drop. Also do not use the B mode. Always use D, unless you have to go down a long steep down grade.

 

[rwb1977]

I also averaged 52 MPG on my first two tanks, and I drive normally... in Alaska, we have a few hills around here. My driving is about half on the freeway, half off. Don't know what others do different, but I'm pretty new to Prius style driving, so I definitely wouldn't consider myself an expert. Hope others can enjoy the same mileage.

 

[neprius04]

What hills in Alaska

I also averaged 52 MPG on my first two tanks, and I drive normally... in Alaska, we have a few hills around here. My driving is about half on the freeway, half off. Don't know what others do different, but I'm pretty new to Prius style driving, so I definitely wouldn't consider myself an expert. Hope others can enjoy the same mileage.

8) Sounds like you live around Eagle River and what is the current price for a gallon of unleaded?

Anchorage is my home.

 

[FarNorth]

RWB1977

Is your Prius a "gold" 2004. I have seen it twice on the Old Glenn but haven't been able to flag it down to compare with our Salsa Red?

Raymond

 

[wvargas]

To RICHARD SCHUMACHER:

I will try to push up the PSI to 42/40 and will let everyone know what happens...

Regarding what you said aboutinaccuracy in the gallos used or miles travelled, I religiously make sure I DON'T press that soft button to reset the odometer.

Something strange I DID notice (I remembered this yesterday) was that after refueling, the "average MPG" and the "miles" counter on the "Consumption" screen were reset to zero automatically. That has never happened to me before.


To MELGISH:
Yes, I will make sure I double check with another gauge...thanks for the advice.

 

[Daniel]

The miles counter next to the mpg, and the mpg, are automatically reset to zero when you fill up. Someone once posted a method of fooling the car into not resetting. So you may have previously done that inadvertently. But the reset is normal. It's useful, also, because the gauge is so unreliable, that it's good to have a direct, automatic reading of how many miles you've driven on one tank. If you always get 450 miles, and one tank you've gone 470 miles and there are three bars showing on the gauge, you'd be wise to distrust the gauge and fill up.

 

[Brian]

Someone once posted a method of fooling the car into not resetting.

Hey, can you find the link for me? I would like to see that.

 

[wvargas]

Well folks...I don't know if it's the tropics or whatever...but I decided to try bring down the PSI of my tires to 30 front/29 rear and voilá, it's back to 43+ MPG.

I checked my Brookstone meter to see if indeed there is a problem with it but confirmed its accuracy.

Now I'm confused. Big time.