I’ll Just Use My Special 78-21-1 Mixture

When I backed the Purple Whale out of the driveway on Sunday evening to make a grocery run I was surprised to find the Low Tire Pressure Light illuminated. The car felt fine, so I knew I didn’t have a flat. I elected to make the trip and if the light didn’t go out by the time we got back I’d check the tire pressures.

As part of the dealer installed options for the Sonata was a $99* charge for the Purigen Tire Service. Which they said improves steering response, handling, fuel economy, and decreases false TPMS alarms. I guess I was supposed to assume that they had filled the tires with pure nitrogen and as proof they did, I got 4 bright green valve caps.

The TPMS light was still on when I got home. Not only was the light on, but the entire info display screen was filled with a dire warning that could not be eliminated, so I grabbed the gauge and checked all four tires. Every one read right at 31 psi. Which didn’t seem too bad, but the door sticker said the manufacturer recommends 35 psi.

One of the purported advantages of pure nitrogen is that its molecules are larger than oxygen so they cannot escape trough the rubber of the tire. One of the first things I did when I brought the car home was check the tire pressure all around because they are often way over inflated for shipping and sitting on lots so the tires don’t get flat spots. When I checked them back in April they all read 35 psi. Did, in a mere 5 months, the tires lose 4 psi of pure nitrogen pressure? Or did the dealer fill the tires with air and try and charge $99 for 4 green valve caps? Or did the whipping the Purple Whales received from Team Turner in Fantasy Football this week knock the air out of the tires?

I filled all four tires back up to 35 psi using my special 78% nitrogen, 21% oxygen, 1% other gases (i.e. the air we breathe) using a cheapo Sears compressor and the light went away.

* The supplemental dealer sticker not only included the $99 dollar tire filling, but a Xzylon Interior & Exterior Protection Package for $699! These figures never were included in the bargaining process as I started at below the internet invoice pricing and gave a little (88¢ a month.) As a matter of fact I didn’t even notice the supplemental sticker until I pulled all the paperwork out of the folder the salesman gave me once I got home.

Last night when I went to the auto parts store I bought a pack of silver valve caps to put on the silver valve stems on the silver wheels.