I've got two answers and you're not going to like either one:

If "fix-a-flat" means the aerosol can, your wife is right and you have problems. They are meant strictly to get the tire up temporarily and get you to where tire can be fixed or replaced. Unfortunately many of these products use a hydrocarbon propellant which is flammable. Many tire shops refuse to work on the tires unless you can produce the can and prove that it had an inert propellant.

If you have SLOW leak, meaning one or two psi a day; noticeably low after a week, liquid sealant such as SLIME is effective and permanent. However, I'm only talking about the real stuff such as SLIME. There are cheaper knock-offs, but you don't know what you're getting. Also, SLIME is a one time deal. If it doesn't fix the leak, you're probably talking new tire. Most shops won't work on a time which has been "slimed". Not because of danger, but because it contaminates the rubber surface making an adhesive repair difficult if not impossible.

I have a friend in rural Northern California who runs a gas station and has this problem from time to time. Customer brings in a tire, is asked about using an sealer, and always says "no". My friend writes "customer says no slime used" on the repair order. When he dismounts tire and finds snot, he leaves it apart and tells customer he owes them $35 for removing the tire to get tire and rim back. He's been sued in small claims three times and has always won. BTW, he won't touch aerosol repairs, can or no can.

I would first look the tire over for any nails or screws, usually you can hear them click as the car is in slower speed. If I found no nails or screws in the tread I would suspect the valve stem. either the seat valve or the stem leaking at the rim or mag wheel.

Fix flat will seal slow leaks IMO no danger in the tire suddenly going flat or blowing out. If you have a nail over time it wears down or maybe thrown out at high speeds causing a bigger hole. Stop leak should stop it quickly, but depending on how big it is could loose air quickly. SO you want to make sure there is nothing in the tread.

now the valve stem Stop leak can actually glue the one way valve shut and make it hard to put air in the tire. There are several ways now to fix a flat. the most popular is plugging, tire shops like this cause it less labor intensive and there profit margin it higher.

You can get a kit and plug it youself. The next and probably the best way is to actually put a patch the tire or replace the valve stem. This is more labor intensive cause the tire has to be removed from the car and then from the rim.

The last way is to use green slim or fix-a-flat. IMO green slim is the best cause it usually shows you where the leaks are cause the green slim will pentatrate to the outside.

Any of these methods will not garrentee the tire will not leak air over time. Even a patch may come loose over time and leak again where the puncture was.

As far as safety, if it's an issue at all? First would be patch, second would be plug, and third chemically sealed. Some put green slim in even it there is not leaks just in case they pick up a nail or screw.

I always inspect my tires before long trips any thing stuck in the tread I pull out and leak check it. if there is a leak I get the tire patched. IMO it's the most relieable. I have had plugs over time leak, IMO if you have a plug use the chemical sealant also, but that's me. with my experience with plugs they seem to start slow leaking over time.

I just took a look in my freezing garage to see if I had a can of fix o flat. All I did was freeze my bare feet. No can, but I wanted to check it for flammability.

I know I used this stuff a few times and I never needed the tire fixed after that. I have my own tire mounting machine, so I know that there is quite a bit of liquid in the tire when I change the old tire and it's a real mess.

As far as being flammable, I would wonder why any company would make it that way, but no can is in the garage, so no answer.

We were 300 miles from home and had a flat tire on top of Mt. Washington, NH and installed a can of fix o flat. Traveled another 1500 miles until I got back home and never had a problem.

Vic: The Slime Tire Sealer also provides another postive , it will dynamically balance and seal . I have used it on most of my Highway Motorcycles for this reason . I also ensure to bring the regular slime brand on all hunting trips as a insurance other than good spares for the vehicles and 4-wheelers and trailers..etc. Actually had two punctures on the last trip and needed the Liquid Leak Fix after my buddy forgot his utility trailer spare tire lol . As for further recommendations , I agree 100% with RC's advice . Hope this helps . If your wife has problems with further leakage just use a plug if the local tire repair shop has problems with internal debris . Heck by the time the leakage returns you will most likely be in the market for new tires. Secondly you could use this tire for your spare . Which should be rotated into your tire placement
anyways.:)

He may have one of the cheap donut spares, so rotating spare in may not be an option? My farther-in-law in the early 90's used fix-a-flat and I mean alot of it. 10 years later I removed the tires. sappling punchures got too big even hard for fix-a-flat to seal so I put tubes in them.

I agree it was kinda of a mess to remove, but not that bad. The side benifit IMO was it preserved the inside of the tires and rims. They were like new on then 14 year old tractor.

Most Tire repair places IMO look for any reason to charge more, most won't even patch tire they want to plug it and charge you the same. IMO Every chemical burns, just depends on how hot it gets, if it burns it's flamable.

I've been plugging holes on my tires for ages. I don't get alot but I've never needed a patch on the inside to seal the hole.

I think the patch is $ icing on the cake $ and done more to avoid potential call-backs.

Yeah I remember when vulcanizing (patch's) was the trend . I think previous posters have hit the nail on the head , Plugs seem to be faster for the tire specialists and they still make a few bucks . I have used plugs myself and they work on most tread punctures . Most people with a little mechanical aptitude can master plugs . Same can be said for tire inflators / sealers.

A good discussion. Some of the Aerosol inflators use propane and it is recommended that you let the air out of the tire and reinflate it at your first opportunity. I have never used a sealant in a car or truck tire. I have found that tires have a tendency to pick up nails during the last 10K miles of their life so I change them when the tread is noticeably worn. I have several pieces of off road equipment and add a sealant when the tire is new. The stuff can't be beat for preventing flats and is the most effective cure for a rim leak. I prefer Berrymans(white) or Prestone(yellow) over slime but either will work. One hint on plugging a tire is to put rubber cement on the reaming tool and insert that just prior to inserting the plug. I always apply a small amount of rubber cement to the plug also. After plugging, trim the plug so it is even with or below the tread. If a plug is left long it has a tendency to enlarge the hole over a period of time.

Ray: Points well taken Bro :)

Stens makes a very expensive "slime" product at about 4 times the cost of green "slime". I bought the green slime on sale for about $20 per gallon. The dosage of green slime vs. Stens slime is the same, so I'm trying the green stuff.

The only thing that concerns me is that there were some comments on here that some of the slimes cause rust in the rim and are only meant for temporary use.

OK this IMO and probably more infor than needed, but what the H#^^, I got some time to kill!

I have never had to change tire on the road, never had a blowout, never had an oil related failure (knock on wood), and probably never ran my tire low on air. ( about 36 cars 2.5 million miles so far.)

I have had slow leaks in tires mostly at the valve stems, did have one patch job done poorly and the patch didn't stick too good on one corner and leaked. Most all the plugs I have had installed leaked in year or two. Again probably cause they were poorly installed.

I will take my tire off and take to a repair shop. why? I don't trust them installing (sure they tell you they torque them (with the Big A$$ air hammer gun), Just like I don't trust anybody changing my oil, (lessons learned for the pass, and yes dealers are no different IMO). If I do get dealer work I take the manager with me to check the fluid level more times than not it's over filled, Some don't even know how many quarts to put in and just dump 5 in.) Words of warning, If you have dealer change you automatic transmission fluid you better check the dipstick after words! (again lessons learned for the pass) My motto is: Smile and comfirm, cause most think you're DA and don't know mechanic's.

Course this is only My opinion and what I have experienced. I keep close track on my tires for my vehicles, yard crap an't that important to me, so I use any easy method to keep air in them. Only rust I have found using chemical sealent (fix-a-Flat) was on rims not painted on the inside. IMO bare metal will corrode requardless is you slim them.

Good Note RC . As for corrosion , painted or not most rims unless you use Nitrogen , rather than compressed air , rust will become a factor with age . More bead leaks are caused by road salt in the winter causing corrosion around the outer bead which after time can cause slow leaks . I really doubt Quality Liquid / Aerosol Puncture Products are a liability , rather a asset in a Emergency Situation .

I've used non-flammable mixture aerosol tire inflators like fix-a-flat to no degree of satisfaction, as the rubber glue contained within them will not set properly without the flammable mixture.
Due to safety concerns of tire-changing mechanics, and lawsuits, many companies including Radiator Specialty, and Fix-a-flat, discontinued the flammable mixtures that actually worked, unlike the newer non-flammable formulas.
A few still manufacture and sell the flammable mixture as I was recently told.
This flammable mixtures can still be successfully used on non-tubeless tires contained on bicycles, etc. with no safety concern, since the tube contains the flammable sealant mixture, and tools are not required to remove them.
I've been looking for some flammable aerosol tire inflater to purchase online or otherwise use strictly in bicycle tires with tubes in them.
Does anybody know any of the brands that still make the flammable mixture and where they are available?