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Low tire pressure after dealer oil change

12K views 16 replies 9 participants last post by  GasGuzz 
#1 ·
About a month ago I had my oil changed at the dealers express service (which took 3 hours).

When wrapping up the paperwork I asked if they checked the tire pressure. The answer was yes, that it is set to the pressure on the door frame. As many of you know that pressure is 32 front and 30 rear.

Today I stopped by the local gas station and checked my pressure with my very expensive tire gauge. It was 28 front and 25 rear.

Either the service tech deflated my tires (related to Tom Brady maybe) or the gauge he was using was defective.

I am going to give them the benefit of the doubt as they seem professional and well versed in their jobs.

My point is to not take their word for it, double check the work. Even professionals, while doing their best, make errors or have faulty equipment.
 
#2 ·
Either their gage is off giving you low pressure, or yours is off, giving you high pressure. If the cars steering feels really light after your inflation, you might want to re-check it at a shop to make sure. If it's yours, replace it. If it's theirs, it would be courteous of you to let them know. from your pressure readings, I can tell they didn't do it intentionally and need to know ASAP.
 
#3 ·
I bet what happened is, they checked the pressure hot, when you first brought the car in. Hot tires should check about 4psi higher than the cold inflation pressure.

I have only been to the dealer once with my car in 3+ years and 87k miles.......My tires were set to 35/33 cold, and when I got the car back, it did not feel right. When I checked, (Within a half mile of leaving the service area) my tires were.......28/25.
 
#4 ·
Correct the temp makes a difference. I check using my own gauge but only after the car has stood overnite, add air using my own portable compressor, same one I carry in the car, then check pressure again.
BTW in 40 or so years I can recall a few times that the pressure was correct after having new tires put on, it's almost always high. Same at the Sube dealer.
 
#5 ·
When I brought my '14 home from the dealership last May all 4 tires were in the 40s.
Every time they do a tire rotation on my or my wife's Outback I have to correct the pressures when I get home.

That's why I have an air compressor with a 30 foot hose in my carport. I check my tires at least every other weekend and make seasonal adjustments for the weather.
It astonishes me how many people I know that never check their tires until something is wrong.
Just the variation from July to January is amazing and most people don't realize it.

John
 
#6 ·
Seeing this thread again got me to thinking. @ 25~28psi, my TPM would be going crazy. Are you sure your gauge is accurate? During the winter, my rear tires @30psi will set off TPM when it gets really cold out, until the tires warm up. Something just doesn't sound too kosher here...
 
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#7 ·
Good point. Seems like the TPMS should be barking, especially about the rears.

OP: What kind of gauge do you use?
The pencil type slip gauges are notoriously inaccurate.
I prefer a dial gauge in one pound increments like a Moroso or Intercomp.
Some folks like digital for ease of reading but I'll stick to the tried and true mechanical dial gauge.

John
 
#8 ·
easy to gain or loose a couple pounds due to the tires cooling overnight,...

I have measured some differences just due to the sun beating on the passenger side tires vs. the drivers side.
 
#9 ·
To add, Running the recommended pressure on your tires is kind of silly. There are so many variables to tires/pressures that it'd be impossible for manufacturers to be able to take them all into account. The recommended pressures are there just to cover their azz's if you screw something up.

For example: If your running across country loaded with 1500 lbs of people/cargo. You'll probably want to bump your tire pressure up. Non OE tires with a higher load capacity will be able to handle more pressure. Some up to 44 PSI.

If your willing to take a little beating from a firmer tire (higher pressure) You can gain a MPG or two.

If your planning a long low speed run thru the snow, lowering your tire pressure will gain you a significant traction advantage.

I consistently run Michelin tires at 35 PSI. It seems to be the best compromise for me. Fairly forgiving ride, with the benefit of a little better gas mileage, and a little longer lasting tire.
 
#12 ·
This is the gauge that I use. Amazon.com: Joes Racing 32307 (0-60) PSI Tire Pressure Gauge: Automotive It is very accurate.

The air pump at the gas station has a digital read out. I don't trust the gauges that I don't own, but this one matched my gauge to the pound.

Keep in mind that my car sat for 2 1/2 hours before they drove it into the bay. It was about 60 deg F that day. And the car was parked in a shaded breeze way during that time.

Can't speak to why the TPMS were not barking at me, although you are right, they should have been.
 
#15 ·
I picked up a 2" wood screw in my right rear Friday and the tpms did not kick in until about 20 psi. As soon as I saw the warning light I pulled over and checked the pressure. It answers why I wasn't getting a warning at 25 psi after the oil change.

I need to check with the dealer about this. That is too low a pressure to kick in the warning. Not to mention I always thought the warning was based on a difference in pressure. Say you are at 30 it drops to 26, that would be enough set it off.
 
#16 ·
I think the TPMS is set at a percentage of full psi, something like 25%. So a tire that's supposed to be filled to 32 should warn at 32psi-25% or about 24psi.

Should be easy enough to check. Next time you are at an air compressor, let air out one psi at a time and see what happens.

My wife's Camry has a section in the manual about how to set the TPMS. Under certain conditions, Toyota recommends using a different air pressure. To recalibrate the TPMS they specifically require that you have the tires set to the desired pressure first, then follow the procedure.

So think about this: The TPMS is factory or dealer calibrated, the factory recommends 32 (I don't have quick access to the car right now, so it might be a little different for real), and TPMS warns at -25%, or 24psi. If you like to drive at a higher PSI, your TPMS will still trigger at 24psi and that would be greater than 25%.
 
#17 ·
That matches my observation. Wife had a screw puncture and it lit up the TPMS at 25psi.
I have a garage 45gal AC so I can measure/fill our cars at the proper temp (w/o having to drive anywhere), and have the OB set at 34.5psi x4. The program also appears to sense rapid drop, 2x now when then temp dropped ~8° in some 5hrs the TPMS tripped at 32psi (the factory spec). Both times I pumped it up to 36psi to turn off the TPMS, and set it back down the next day.
 
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