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2012 Soul + automatic
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48 Posts
Discussion Starter #1 (Edited)
I put air in my tires for the first time.

The door jamb says the tires should be at 33 psi.

When I went to put air in my tires, the gauge attached to the air pump nozzle said all the tires were around 36 psi.
The tires were still cold.

Did the manufacturer intentionally put 36 psi? Should I put 33 psi or closer to 36 psi?

I would like to know what psi will give me the best gas mileage.

Are the gauges attached to the air pump nozzle usually accurate or should I buy one?

Is the psi noted in the door jamb for the vehicle or tires?
 

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10 Optima LX, 12 Sedona LX
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1,414 Posts
Higher pressure will give you better fuel economy, but with other side effects. Higher pressure will cause a rougher ride, and if too high can cause the tires to wear the center of the tread, causing them to need early replacement. From my experience, the Souls tend to wear the OE tires good if set to door pressure(33) or maybe a few pounds higher(34-36). This depends on driving conditions as well. Where I'm at the roads are fairly twisty, so the higher pressure keeps the tires from rolling as much, preventing edge wear.

I would buy a good air pressure gauge and keep it in the car, as most gas station pump gauges are not accurate.
 

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Cerato S Hatch Auto
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1,236 Posts
The maker's recommendation is usually on the low end of the scale, mainly in the interests of a smooth ride. I've always used 36 PSI front and back on most cars, measuring the tyres cold (that's about 20°C where I live). The pressure will increase about 1.2 PSI for every 10°C rise in temperature. Don't forget that tyres sitting in the sun will get hot, even on a cold day, so make allowance for that when checking pressures.

The PSI on the placard is the car maker's recommendation. Tyre makers sometimes advise on maximum pressure allowable (usually about 40 PSI).

Tyre gauges at servos take a real beating, and are sometimes wildly inaccurate. Some places have digital gauges which are remotely located, and these are likely to be more accurate. Best idea is to get yourself a reasonable quality gauge (not plastic) and test it against several likely "good" servo gauges. Mine seemed to be within 1 PSI of the true pressure. (Absolute calibration is expensive).
 

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former owner of a 2016 Soul SX 2.0L - Caribbean Blue
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I answered the same questions you posted on the Soul Forum.

You really need to read labels more closely, it clearly states the tire size and the psi for it, how much more clearer could it get?
 

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Cerato S Hatch Auto
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Can't add much to my older post. 36 PSI all round is still good for most cars. Although most advice calls for lower pressure in the rear on FWD cars, I've found that it doesn't matter; the wear rate at the rear is much less than at the front, so a little extra pressure is of no consequence. The spare gets a few extra PSI so that it will be OK for 6 months or more without checking.

I've never actually checked fuel economy vs. tyre pressure, but there's likely to less rolling resistance with higher pressure. One complicating factor is that the rolling radius will also increase, and this odometer variation would need to be taken into account when checking fuel consumption.
 
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