Do the Fix-a-Flat spray cans have a permanent effect?

After putting fix a flat in the tire the instructions tell upo to drive right away to force the sealer around the tire to seal any puncture. The centrifugal force of the tire spinning won't push the sealer around the bead area where the slow leaks are. You need to have you r tire removed, the rim wire brushed, and bead sealer put on the rim before remounting the tire and balancing it.

Don't use fix-a-flat unless you have an emergency and don't have a spare. It's better to get the tire fixed properly. Several people have told me that the fix-a-flat will ruin a tire so it can't be repaired using a patch.

Fix-a-Flat is not intended to be a permanent repair. It is intended to be an emergency leak repair that will get you to the tire shop for a permanent repair.

Fix-A-Flat will actually attack the tire. My daughter bought a beater for her first car and I could reach my hand through the melted sidewall of the spare tire; our tire guy said it was from Fix-a-flat.

for a couple of bucks more than the can costs you can get the leak fixed, call a couple of tire shops to see what they charge

Yep, it will fix it. Slime works longer. We run Slime (or similar) in some tires that get punctures frequently. Your tire guy will hate you when you get new tires. My son took one of the tires to get replaced and the tire guy made him dismount the tire, clean the wheel, and mount the new tire.

No, never. The leak must be patched.