I live in CA and have an 89 Chevy Blazer. I have used GTP before smog checks twice now. Last Monday I put it in a 3/4 full gas tank and drove for 160+ miles to not quite near empty. Filled the tank to only 3/4 full because of the price of gas. Got my smog test and it passed quite well. Prior to smog checks I get a tune up and oil change. I don't know anything about cars except to check all fluids regularly. Two years ago it barely passed so I expected to fail this year. I do believe GTP makes a difference and will use it again.

Bought 2 bottles. Followed instructions and did it two times. Didn't work or improve performance in any way.

Used this on a 155000 mile 4 cyl car I bought, which only had cheap gas run it. The 'engine' lite was on, bought new gas cap, new exhaust cat-back. Used only Shell gas, still lite on. Put this CRC stuff in it with 1/2 tank of shell, lite flickered, came on intermitatntly. Put 2nd can in 1/2 tank Shell, lite WENT OUT stayed off. Use only Shell gas. 3 years later, started running rough,left me stranded twice. has 165000 miles, did same thing-1 bottle CRC to 1/2 tank gas. PROBLEM SOLVED. I highly recommend this product. It is cheaper than a catalytic converter....and use shell gas, not cheap crap.

This doesn't really work as advertised, but might be helpful if you just get some bad gas into your tank. I had a bit of a fuel injector issue and it helped a bit but didn't exactly get me out of the repair job (cleaning/flushing fuel injectors).

i use this all the time for my car to pass the emission test. it really work and i have no trouble apply it into my car for it to pass emission. the other thing is a pain it makesure you drive it around so you get the mile you need to paste emission test but otherwise is the best thing to buy.