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Discussion Starter · #1 ·
Had my 8K service last Satuday, Dealer set the tire pressure to 32PSI. Tonight temperature dropped down to 5 degrees and the tire pressure warning light lighted on. Should I increase the PSI?

And ever since the temperature dropped down to below 18 degrees couple weeks ago, the fuel consumption has gone up A LOT. During summer it was 4.5L/100km and these few weeks it’s around 5.5L/100km.

 

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Celsius or Fahrenheit? Really doesn't matter. ;)

Anyway, Inflating the tires to more than the factory recommended pressure seems to be the norm rather than the exception. Anything up to the maximum listed on the tires is safe (cold inflation pressure). My dealer even inflates them higher than factory recommended, but not too much! It should keep the pressure light from coming on if you put another 5 lbs. or so in. Added bonus, increased fuel economy, but the ride will be a bit harsher. :)
 

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all pressures should be set to 36psi....
 

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I believe the rule of thumb is for every 10 degrees (F) drop in temp., your pressure in your tires drops by 1 PSI.
 

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all pressures should be set to 36psi....
I don't have a problem increasing the tire pressures over the recommended, but why all the same? The rears were set to 1 psi lower than the fronts for a reason, no? Therefore shouldn't you recommend setting the rears at 35 and the fronts at 36?
 

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I'd be willing to be that, when the dealership set the pressure to 32, they didn't reset the TPM system at the same time. If that's the case, then the TPM system already had them being 10% low. My understanding is that the sensors go off when they are 25% lower than the baseline.

If the were filled when inside of a heated shop, after the car had been inside for a little while, then the 1 pound drop per 10 degrees fahrenheit has to be calculated based on the shop temperature when the tires were filled, not the outside temperature. So, an additional 15% drop in cold weather probably isn't that unusual.

If temperatures are expected to remain cold in the short term future, I would definitely refill them to you desired psi. You should do so in the morning with the tires cold. If you can't fill them at home, before driving, you should check the pressure of each tire at home before driving. Then when you get to the gas station, you should check the pressure again. You should then add the difference between the first reading and the second reading to the desired psi when you fill the tires up.

After you fill the tires to the desired pressure, you should then reset the TPM System. Instructions can be found on page 521 of the owner's manual.

http://drivers.lexus.com/t3Portal/document/om/OM76004U/pdf/sec_04-03.pdf
 

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The dealer probably didn't reset the TPMS system after they adjusted your tire pressures, which is why the light came on after getting it picked up from the dealership.
 

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Discussion Starter · #8 ·
okay, I am going to check the tire pressure and reset the TPMS tomorrow.

so BTW, do u guys experience any fuel consumption increase this past few weeks? I really want to know if it's the temperature or just my car
 

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Gasoline is reformulated in the winter maybe has some effect.
 

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I'm driving 41 all around. Ride quality is still great and comfortable. Tires say Mac is 51. And yes I'm using stock factory tires. They got about 13,800 miles on them.
 

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I don't have a problem increasing the tire pressures over the recommended, but why all the same? The rears were set to 1 psi lower than the fronts for a reason, no? Therefore shouldn't you recommend setting the rears at 35 and the fronts at 36?

I would not worry about that because most if not all pressure gauge on market can't tell the difference within 1 psi anyway
 
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