Whoever came up with that policy is clearly an idiot
LTs typically get at least 50psi . . . and Discount Tires probably has plenty of people who drive vehicles that require such tires
One size does not fit all 
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That’s what I said. The policy may change for vehicles that require more air, I didn’t specifically ask him about that. My tires are 30psi standard and he put 34 in, that’s when he explained to me the policy and nobody there knows why its the policy. I like the TPMS explanation, but it can unevenly wear your tires. During icy conditions it’s especially stupid. He guessed it was so that people would have to come back for tires more often.
6 psi over the decal pressure seems a bit much. At the shop I manage we air up the tires to 3 psi over the recommended pressure. That’s because the spec is for a cold tire that hasn’t been driven, and every car we work on has been driven first.
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I think everyone here has presented all too generous albeit plausible explanations for this incident. The simple answer is " Because this dealer has at least one person working in his shop who is a MORON".
Good for you OP for double checking the shop’s work. There’s several possibilities for error as mentioned above. Or it could just be a mistake. No simple way to tell if the tire pressure gauge you are using is more or less accurate than the one they are using, that’s one problem. And if it was hot that day they may try to pro-actively compensate for temperature changes, but that seems pretty far fetched. As you mention, it is pretty easy for you to just let out a little air.
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“No simple way to tell if the tire pressure gauge you are using is more or less accurate than the one they are using, that’s one problem.”
True. Mine’s an electronic one that reads to tenths of a pound, not a dial type. (Can’t understand why dial types haven’t all gone away.) But it can still be inaccurate. At least it’s consistent. It’s 32.0, not 36, 36.5, 36.5 and 37, when I set the pressure.
“And if it was hot that day they may try to pro-actively compensate for temperature changes.”
It was warm, in the mid-80s (in San Antonio that’s “warm”), but I went back and reviewed all the work orders for my oil changes, and on all of them, except where I asked for the tires to not be checked, the service writer had always written 38 psi. Summer, winter, didn’t matter, 38 psi.
This wasn’t the first time I let air out of the tires, but the first time I thought about trying to understand why it was necessary. Right now, the TPMS theory makes the most sense.
Digital readouts don’t make gauges accurate. Actually the mechanical bourdon tube dial indicators seem to be the common industrial/professional choice. They can be calibrated easily.
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among my colleagues, the digital inflator gauges are quickly becoming the new “norm”
at least, that’s what I’m seeing
I guess I’m not a true professional after all 
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Toyota advises their technicians to use dial type tire pressure gauges.
Inflating the tires to 32 PSI during the heat of the day will result in 50 customers returning each day after two months with the low tire pressure warning light on, nobody has time for that.
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Every road tractor in our fleet had a 20 ton bottle jack under the passenger seat, it was red, no idea what brand. We were running 1100x22 tires(old size) The standard tire at the time was 1000X20 for most trucking companies. We also had 6" spacers between the wheels instead of the 4 1/2". We loaded HEAVY, and we had been blowing tires by rubbing the sidewalls together. Did I mention that NY State had no permanent scales?
Whe had a mounted spare mounted on the catwalk behind the cab over the fuel tanks. After we changed a tire we put the blown one in the empty spare tire rack under the trailer for the shop to deal with later. Ever rig that left our terminal had 2 lug nuts on each wheel checked with a torque wrench set at 300 lb while the mechanic fueled it. If one of the lug nuts moved, all were torqued. We never lost a wheel due to loose lug nuts after they started doing that.
The first year I worked for that company, I saw 5 loads leave our terminal with over 100,000 lb payload on the trailer. Our van trailers had twice as many ribs as a standard trailer and weighed 13,000 lb empty compared to10,000 for a standard trailer.
My Kia dealership is the opposite. They say they cannot deviate from the 32psi factory spec. I schedule my November dealer service just before my trusted regional tire shop 5,000 mile free rotation. I always decline the dealership free tire rotation. The tire shop has no problem with 35psi inflation. Our Winters are fairly mild but if the temperature gets to 25F 32psi will reach 29psi and trigger the TPMS. The tire shop rotation includes checking tire balance on their force balance machine and driving the car in figure 8s in both directions before re-checking proper lug nut torque. Since the year I was born (1952) their business model has remained complete customer satisfaction.
Does your car still have the original tires? New tires may require a different pressure. When I get new tires I always ask the dealer what pressure to use and it’s always something different than what I had before. The dealer said to use 36 psi on my current set.
If you get the same size tires, the recommended pressure doesn’t change. If the dealer says otherwise, they’re not to be trusted.
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Ply rating is a very significant determinant of tire pressure @texases. But of course passenger car sizes are for the most part 4 ply rated but SUVs on the other hand might have 6 or 8 ply ratings with pressures of 45-65 psi.
Right, but if they got the right replacement tires, the pressures shouldn’t change. Passenger vehicles, that is.
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I believe the OP did change tire/wheel size on the vehicle but both available sizes have the same cold inflation pressure, 32 PSI.
On the positive side you don’t need a pump to adjust the cold tire pressure when they put in 4 PSI extra, doesn’t seem like a big deal.
For a 6 psi difference there would have to be 60 degree difference in temp. 10 degree difference = 1 psi difference.
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You seem to be a lot closer to the situation these days @texases, but from my current position on the outside looking in I see that SUVs are taking over the roads and those low profile oversize wheels/tires look as though they may be be heavier construction higher pressure tires.
Back in the GOOD OLE DAYS I could easily recognize that Suburbans and similar vehicles had 16" or 16.5" tires that were load range C or D. The narrow tread and wide sidewalls were unmistakable to mechanics at the time. But today the tire industry has again changed designations to keep the public in the dark enabling tire retailers to sell us a “pig in a poke” as we get lost in all the jargon. Luckily for now my vehicles are old enough to have metric 15 inch tires.
Now that’s something I didn’t know. (Well, among a million other things.)
I’m now of the opinion that the dealership wasn’t trying to fill the tires correctly, but was trying to fill the tires so the TPMS error light wouldn’t come on.
Some time ago on a Sunday afternoon I stopped at a quick mart and a faded mini fan filled with blue haired ladies was blocking 3 parking lanes and their voices indicated they were troubled and in a few seconds it was obvious that the TPMS was on and they found the answer in the owners manual but were clueless what to do. Luckily I was slow to get involved and a young man took control of the situation and had the ladies move over to the stores 50c air pump. It’s possible that the warning light saved the ladies from spending time on the shoulder but for them and a great many others full service stations would be a great deal of help.
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