Just before I handed back my 2013 Acura ILX hybrid test car, I drove it, with my elder daughter in tow, down to the local burger joint. Pulling into the lot, I clipped the curb and immediately lit up the tire pressure warning light. Damn, a flat.

I’ve changed a zillion tires, including one on a swaying bridge between Oregon and Washington states in the pouring rain. Piece of cake, right? Wrong! The 2013 ILX Hybrid is one of a growing number of cars that saves weight by abandoning the fifth wheel. No more spare. I’m not sure this is progress, but I understand the reason for it. The main concern with spare tires is that they add weight and affect fuel economy as carmakers are trying to get to 54.5 mpg in 2025.

Acura tells me, “To save weight and space, while adding convenience, your Acura has replaced the traditional spare tire, jack, and lug wrench with a tire repair kit…. Most flat tires can be repaired sufficiently until you can drive to a service station for a more permanent repair.” Wrong again!

The hole was in the sidewall, and the kits aren't useful to fix that kind of damage. The kit is a battery-operated pump that injects sealant into the tire to patch the leak, and it wasn’t up to the task. I also tried to use one on a Saturn Vue Hybrid a few years ago, and at least it half-inflated the tire so I could limp it to a gas station (at no more than 50 mph). One of the worst things about these kits, some experts tell me, is that they can really mess up a tire. The kit may get you out of the emergency, but many tires are junk going forward.

According to one of the kibitzers at the Pontiac Solstice forum, “Many shops refuse to patch tires that have had sealant used in them just because it’s a pain in the ass.” Others say the sealant can damage tire pressure sensors, or make it impossible to use inner galvanizing patches. In any case, the sealant has to be removed, and that gets harder once it’s been there for any length of time.

On the sensor issue, I’m not sure I find this statement from Slime, a maker of kits, to be reassuring. “Slime Tire Sealant may come in contact with the sensor in a way that renders the sensor TEMPORARILY inoperable until it is properly cleaned, inspected and re-installed by a tire care professional.”

Kurt Berger, engineering manager for consumer products at Bridgestone, told me that some new car owner’s manuals specifically caution against reusing tires that have been sprayed with sealant. And he added, “Our policy on any kind of sealant product is that it voids the tire warranty.” Wow, that means that in some cases if you use equipment provided you by the automaker, you’ll be out of warranty for another product they supplied.

Another problem is with price gouging to replace the bottle of gunk that is a one-time use. A Nissan Leaf owner went to his dealer after a flat and was quoted $200 for the gunk and $600 for the whole kit, when the sealant is $28 at Tirerack.com and the whole kit $78.

On a recent Bridgestone press trip, I asked Mike Martini, the company’s president for original equipment tires, if we’d seen the last of the spare tire. Are you surprised that he said it’s history, along with the CD player?

“My personal opinion is yes,” Martini said. “The fifth tire does not offer an efficient use of space. It’s not just the tire; there’s also the jack that has to be carried around. Right now we have 10 percent tire sealant kits in the U.S., but it’s 40 percent in Europe. American consumers are still not comfortable with them, but they can be a fabulous way to solve the fifth wheel issues that all the automakers want to address.”

We’ve been evolving toward jettisoning the spare tire for 30 years, since the first mini-spares were introduced to save weight and space. I still think mini spares are terminally weird looking, and they’re supposed to be used only for short distances, but they’re put on the car in the traditional way, with a jack. That doesn’t do much to get the consumer out of the tire-changing business.

My guess is that fewer and fewer Americans even know how to change a spare — it’s like driving a manual transmission today. That means that favored tech going forward will make it super easy to get back on the road.

We need a solution that works, though, and I’m not sure tire sealant kits are it. What about run-flat tires? The most common technology here, at first seen on luxury cars, is a reinforced tire with self-supporting sidewalls. According to Yokohama Tires, in 2011, they were installed on half a million cars, and that’s likely to grow to 650,000 by 2015. But Bridgestone’s Berger told me that run-flats are only about 1 or 2 percent of the original equipment market now.

There have been complaints about run-flats, too. According to Business Fleet, run-flat tires are heavier than standard tires by about four pounds each (which is a savings when a spare is 40 pounds), and get criticized for creating a rough ride. Replacing them is also expensive, as is repairing them. Automakers are trying to redesign suspensions to accommodate run-flats.

Another weird thing about run-flats is that because of the stiff sidewalls, you can’t visually tell when they’re losing air. The tire pressure monitoring system (TPMS) becomes vital.

A lot of new information to absorb, and I’m not sure my feeble brain is up for it. Here's a British video that tells you how to use a tire sealant kit, if it isn't immediately obvious. Note that our narrator says that 85 percent of "punctures" are in the tread. But both of mine were in the sidewall, making the kits useless:

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Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.

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