[Qmulus]

"Fix a flat" is awful stuff. Just ask anyone at a tire shop. ANY type of spare that holds air is better. Tire goo is only useful on small leaks, where a plug/patch kit is a better solution. The whole purpose of the temporary spare is to have something to get you home or to service. Chances are that the spare in your Boxster is just fine, even if it isn't new.

I personally have a plug kit in each of my cars. While it isn't something that I would expect my wife or daughter to be able to use, I have repaired nail/screw holes on the side of the road with them on more than one occasion, and usually didn't bother having them "properly" patched later on. The two times that wouldn't have worked were when the tire had been damaged beyond all help. Once my wife hit a piece of rebar that put a huge hole in the tire and the other I hit a piece of something that came off of a truck that ripped the sidewall open. Without a spare in the car those times it would have meant a tow truck. I tell my wife and daughter that if they have a flat, they call me first and if they can't get a hold of me then call roadside assistance. When my wife hit the piece of rebar on the way to the airport she called me first, then called our insurance company's roadside assistance to see if they could come quicker. I got to her before she was off of hold, switched vehicles with her to get her on her way and then swapped the spare. It was a mere 20 min inconvenience for her, and not a big deal to me either.

Here is another example. A friends daughter picked up a nail while away at school and thought she would be smart and called a friend to bring some fix a flat type stuff to put in the tire. The car had a full size spare, but she didn't know how to change it. She had a hard time with it and while it was mostly inflated, by the time she got to a tire store the sidewalls had been badly worn. On top of that, the fix a flat destroyed the tire pressure monitoring sensor. So, what should have been a simple repair that many tire shops do for free cost a new tire, a new tire pressure sensor and a charge to clean the rim of the "goo" that had been sprayed in. All in all, it cost close to $500 and hours of inconvenience.

My recommendation? Keep the temporary spare and make sure it is pumped up at least to the recommended pressure (when was the last time you checked air in the spare?). I put mine about 5 PSI high and adjust if needed when I put it on. Having an underinflated spare is not much better than not having a spare at all.

If you want to be really good, also keep a plug/patch kit in the car along with a diagonal cutter to pull out nails/screws/whatever and cut off the plug and a compressor.