Tire Sealant Review: Roadside Heroes and Those That Will Leave You Flat
Consumer Reports evaluates several popular sealants, from pressurized cans to complete kits with compressors
A flat tire is always inconvenient and often dangerous, risking loss of control while driving or collision while performing a roadside repair. Adding to the drama is the reality that many recent cars don’t even come with a spare tire. For many motorists, the best tools to fix an ailing tire are a phone, roadside assistance membership, and a spare tire or tire sealant kit, which can be used to fix small holes and refill the deflated tire. There are aftermarket sealants, as well. These typically cost around $10 for a pressurized can to around $80 for a full kit with a portable tire inflator, making them an attractive addition to an emergency kit that is kept in the car. But our testing reveals that not all tire repair kits work as expected. This is a shame, because they have great promise, and the alternatives bring real compromises.
These days, it is important for drivers to have a plan for dealing with a flat tire before it happens. Reviewing records on Consumer Reports test cars going back to the 2017 model year revealed that about 62 percent came with a temporary spare, 15 percent had a sealant kit, and 11 percent were equipped with run-flat tires and no spare. Just 9 percent came with a full-sized spare tire—the only solution that allows you to continue your travels, without stopping at a service center for a professional repair or new tire. (If you have a spare tire, be sure to check and adjust its air pressure regularly, or it may be flat when needed.)
Types of Tire Sealants
To see how the latest products work, the Consumer Reports tire team evaluated seven common sealant models among three distinct types. Each is readily available in stores and online, and we bought multiple samples of each one for the project.
Pressurized-can sealants ($7 to $20), such as the ubiquitous Fix-a-Flat, are one-time-use products that have a dispensing tube that screws to a tire’s air-inflation valve. The sealers we bought claim to seal a hole and partially inflate the tire.
Tire-sealant kits ($24 to $80) combine a portable 12-volt air compressor and a replaceable container of sealant. Many new cars supply this kind of kit in lieu of a spare tire.
Liquid tire sealants ($9-$14) is a liquid sealant poured through the valve stem of a tire/wheel, then inflated with a compressor that's not included.
No attempt should be made to repair a hole larger than 6 mm in diameter or a cut or hole in a sidewall with these products. Your only option is to replace the tire with that kind of damage.
If you use a tire sealant, you should get the tire professionally repaired or replaced as quickly as possible—typically within 100 miles or as directed by the product.
Sealants coat the inside of the tire and wheel with a messy residue, which a tire shop has to clean out, possibly causing extra expense. They can potentially gum up the tire-pressure monitor sensor (TPMS), if so equipped, risking erroneous readings. Most products specifically claim that they are TPMS safe.
Do be aware that some sealant products have expiration dates and will therefore need to be replaced periodically, even if not used.
Should You Buy a Tire Sealant?
In a pinch, a pressurized can sealant may be able to fix a small hole and allow the car to limp to the tire store for a full repair or tire replacement, provided you have a compressor to top off the tire pressure. The better investment is a tire sealant kit that has the ability to fix a punctured tire and inflate it to the recommended pressure as specified by your car’s tire information placard found on the driver’s door jamb. In addition, the kits evaluated can be safely stowed in the car, even a hot car. On a vacation, or during a busy day, a tire repair kit with a compressor would allow you to continue on route. They cost more, but based on our experience, the price is worthwhile.
There are limitations to what can be fixed with a sealant product. A large hole, multiple holes, or a sidewall tear can be beyond the capabilities of these products. Ultimately, spare tires and run-flat tires are better alternatives. When buying a car, it is worth checking to see what it comes with. In many cases, you may be able to pay extra to have a spare tire added.
“Based on these tests, I would buy a tire repair kit with a compressor to keep in the trunk,” says Ryan Pszczolkowski, a tire technician at Consumer Reports. “But you can’t beat a true spare tire as a solution to any tire problem.”
Read on to see our findings. And see how we tested, below.
Tire Sealant Kit Reviews
The tire sealant kits include both a can of sealant and a compressor that work together. The sealant is connected to the tire via a screw-on tube, and the compressor is plugged into a 12-volt power accessory port. With most kits, the compressor forces air through a container of tire sealant into the flat tire.
Unlike the pressurized sealant cans, these kits can pump a truly flat tire up to its recommended pressure. And because the sealant isn’t pressurized before you use it, you can keep the kit in your car. (Pressurized cans risk rupturing if left in a hot car.)
Another plus is that when you’re not using it to pump sealant into a flat tire, the compressor can inflate other car tires, yard and recreational equipment, boat trailer tires, and so forth.
The tire sealant kits that we evaluated claim to be safe on tire pressure monitoring system (TPMS) sensors. (We did not verify this in our evaluation.) They each have their own usage guidelines. For instance, tires fixed with the airMan kits should be limited to 120 miles of driving at speeds no more than 50 mph. The Slime Smart Spair Emergency Flat Tire Repair Kit recommends temporary use to no more than 100 miles or 3 days from date of the tire fix, and the Slime Flat Tire Repair Kit Digital Series claims use limited to 500 miles, according to Slime's website.
Each proved effective solutions for the large punctures, except for the Slime Flat Tire Repair Kit Digital Series, which worked well only with the smaller hole size.
airMan ResQ Pro +
This kit sealed the large 5.8-mm puncture and inflated the tire quicker than other units. Simple to use, the airMan ResQ Pro + comes in a self-contained package and requires no assembly, and it comes with a carry case. It was the favorite among the team.
Where to buy: Grainger
airMan ResQ Tire Repair Kit
This lower-priced airMan kit had similar performance to the airMan ResQ Pro +, but it requires assembly of the sealant container to the compressor. We think the extra money is worth it to buy the ResQ Pro+, because you might need to use this product in less-than-ideal conditions—such as on a dark, rainy night—alongside the road. Plus, you have to disassemble this to fit it back in its case. Spend the extra money.
Where to buy: Amazon
Slime Smart Spair Emergency Flat Tire Repair Kit
Priced less than its evaluated rivals, this kit sealed the large 5.8-mm puncture with ease. However, it requires removing the tire’s valve core with an included hand tool, then squirting the sealant liquid through the valve stem, re-installing the valve core, then inflating the tire with the compressor. Removing the tiny valve core adds an element of risk of difficult removal and misplacing it during the roadside repair. It is more cumbersome than the airMan products. The savings aren’t worth the concession in our view.
Slime Flat Tire Repair Kit Digital Series
As the name suggests, this kit comes with a digital pressure gauge in the compressor unit. (A cheaper dial gauge model is also available, but we did not evaluate it.) There is no need to remove the valve core as with the cheaper Slime Safety Spair Emergency Flat Tire Repair Kit. Like the airMan products, sealant flows into the tire through the compressor. The results were mixed for this kit. Our first attempt to seal a 5.8-mm puncture was not successful. The tire leaked after filling with sealant, and it was almost totally flat in 24 hours. We did a retest on a brand-new tire and had better results with only a slight loss of pressure after a 50-mile drive. We checked the pressure 24 hours later and found the tire to be down 10 psi from the recommended 35 psi. We then ran the test a third time with a 2.4-mm hole, and we found the kit to easily seal the smaller puncture. Based on our experience, we would choose one of the airMan kits over this.
Liquid Tire Sealant Reviews
Liquid tire sealants are inexpensive, but you'll need a compressor or portable tire inflator to inflate a tire after the sealant application. Best use would be as a backup at home.
Slime Tire Sealant Thru-Core Technology
The sealant couldn’t plug a 5.8-mm puncture, but we had success with a smaller 2.4-mm puncture. This is an inexpensive solution to small punctures, assuming you own and carry a portable tire inflator. But because of its limitations, we’d look to a kit or pressurized can sealant.
The biggest advantage of pressurized-can sealers is that they are widely available and cheap. They cost just $6 to $12 for a can designed for most car tires. For a few more dollars, 18- and 20-ounce cans are available to service larger pickup truck and SUV tires.
Fix-a-Flat has become synonymous with pressurized-can sealants. These products are widely available, but their test results disappointed. Fix-a-Flat was able to seal the smaller 2.4-mm puncture with a minor loss of pressure in a 24-hour period. However, it could not seal the 5.8-mm puncture, and it could not inflate the tire without topping off with a compressor. It is easy to use, but the performance limits its usefulness. (Larger cans for pickup truck and SUV tires cost a few dollars more.)
Super Tech Tire Sealant & Inflator
The Super Tech Tire Sealant & Inflator from Walmart is by far the cheapest product we tested. And its performance did not deliver. It proved easy to use, but it could not effectively seal a 2.4-mm or 5.8-mm nail puncture. The can does not specify what size puncture it would seal. When asked, Walmart did not tell us what size hole it could seal. Similar to the Fix-a-Flat product, a compressor was needed to top off the tire pressure to the car’s recommended pressure.
When we asked the retailer about this product, which carries a Walmart trademark, a spokeswoman wrote, “Walmart uses accredited third party laboratories to validate that all regulatory and compliance requirements are met in addition to testing the performance of the product. The feedback we received from Consumer Reports as a result of their performance testing of this item has provided us with an opportunity to further review our protocols to continue to drive improvement in our testing methodology.”
We recommend considering any of the other products evaluated over this bargain-priced sealant.
Where to buy: Walmart
How We Tested
Most of the products we evaluated claim to seal punctures up to 6 mm in diameter, though others have no specific claim. Product tests were performed on new tires with a 5.8-mm diameter nail puncture that caused the tire to go flat. We then attempted to seal the puncture, following the product directions.
Tests were done on 16-inch all-season Sentury Touring tires placed on our 2015 Toyota Camry.
We used a nail that measured 5.8 mm in diameter. (Some products were evaluated with a smaller 2.4-mm diameter nail if they couldn't seal the larger 5.8-mm nail hole.) The nails were welded to a flat metal plate. The Camry was lowered from a car lift onto the nail to provide a consistent puncture in the same tread area for all evaluations. Once flat, the tire was sealed and inflated to the recommended 35 psi, then driven a short distance to coat the inside of the tire with sealant. Tire pressure was checked again, and if no loss of pressure was measured, we drove 50 miles, and parked the car overnight and checked the tire pressure the next day.
Our evaluation clearly showed that the tire sealant kits were far superior to pressurized-can sealants. They were able to seal a larger puncture and have a compressor to inflate the flat tire to the recommended tire pressure of 35 psi for our Toyota Camry.
The pressurized-can products could inflate the tire only to less than a quarter of the pressure recommended. Plus, they were not able to seal the same 5.8-mm puncture as the tire sealant kits could; tires continued to lose pressure after applying the sealant.
If you are planning to use a pressurized-can product, it is wise to have a compressor handy to top-off the tire to its recommended inflation pressure. Further, the pressured-can products we evaluated warn not to store them inside a car because of temperature concerns; this could limit their use to your driveway.
The liquid tire sealant is essentially a pressurized can that inserts sealant through the valve of the tire, but it lacks the ability to inflate the tire. It is necessary to have a compressor on hand to complete the repair. We found this product, like the pressurized-can products, not able to seal a 5.8-mm nail puncture.
The products were more successful with the 2.4-mm hole made with a finishing nail. Both the Fix-a-Flat pressurized can and Slime liquid sealant held pressure to within 1 psi, an insignificant loss after 24 hours. The Super Tech pressurized can product failed to fully seal the puncture, with the tire down 7.6 psi within the same time limit. As in the initial test with the larger framing nail, neither product had enough pressure to fill a tire to our 35 psi pressure without topping off with a compressor.