Here's why variations *do* exist, and why a large discrepancy should be investigated:
* Tire Size and Load Rating: Different tire sizes and load ratings (indicated on the tire sidewall) require different pressures to support the vehicle's weight and provide optimal handling and fuel economy. The sticker on your driver's side doorjamb usually specifies the correct pressure for *your specific vehicle's tires*, not a generic recommendation.
* Vehicle Weight: A heavily loaded vehicle will require higher tire pressure than a lightly loaded one.
* Temperature: Tire pressure increases with temperature. The manufacturer's recommendations often account for a typical operating temperature range, but significantly different ambient temperatures can affect pressure.
* Measurement Inaccuracy: Gauges can be inaccurate. Both the manufacturer's recommendation and an auto shop's measurement may have some margin of error.
* Misunderstanding of Recommendations: The sticker on the driver's door jamb indicates the *recommended* cold tire pressure. An auto shop might inflate to a slightly higher pressure to compensate for anticipated temperature increases throughout the day, but this should be a relatively small adjustment (a couple of PSI, not 14).
* Incorrect Tire Type: If the wrong tires are installed (different size, load rating, etc.), the recommended pressures will be wrong.
If you're seeing a 14 psi difference, don't ignore it! Here's what you should do:
1. Check the driver's side doorjamb sticker: This is the ultimate authority on the manufacturer's recommended tire pressure for *your* vehicle.
2. Verify the tire size and load rating: Make sure the tires installed match the specifications in the owner's manual and on the doorjamb sticker.
3. Use an accurate gauge: Get your tire pressure checked with a reliable gauge, not just the one at a gas station.
4. Check the temperature: Measure tire pressure when the tires are cold (before driving).
5. Consult your vehicle's owner's manual: It contains valuable information on proper tire maintenance.
6. Seek professional advice: If you're still unsure, consult a qualified tire professional or your vehicle's dealership. A 14 psi discrepancy suggests a problem that needs to be addressed to ensure your safety and the longevity of your tires.
