Driving a well-maintained, regularly serviced automobile is the best method of passing an emissions check; but what are ya, some kind of square? Instead, use the tips below to try and squeeze your carbon-spewing jalopy under the smog-check wire. And if they don’t work, do not try the less-than-ethical, probably illegal smog test cheats I’ve included for informational purposes only.
Ethical smog test tips
These are perfectly normal, totally above-board tips for passing an emission test.
Test with a hot car
Running your engine before the test is probably the most useful method of maximizing the chances of passing. A hotter engine means more fuel is burning, so less gunk is coming out of the tailpipe. Before you pull into the testing center, cruise around for about 20 minutes, ideally at highway speeds.
Try a fuel additive
Fuel additives are designed to increase efficiency by cleaning carbon residue from your car’s engine and exhaust path—a more efficient engine means lower emissions and hopefully a passed smog test, so dump some in your gas tank before you pull in to the smog garage. A “general” gas additive like Chevron’s Techron should help, or you could go with something specific, like CRC-Guaranteed Emissions Formula.
Use low-octane fuel
Don’t fill up on super-premium gasoline before your smog test. Go for that cheaper, low-octane stuff the peasants put in their Kias. It burns faster than higher octane fuel, and thus produces fewer emissions.
Change your oil
If you’re a decent person who changes your car’s oil regularly, it probably won’t matter too much, but if you’re a shameful reprobate who doesn’t keep up with your car’s recommended maintenance schedule, change the oil. The fumes from your sinfully filthy oil compartment can infect your engine and come out in the emissions.
Add some air to your tires
Low tire pressure or uneven inflation of tires can negatively affect how your engine is running and thus its emissions. Plus, in some states, smog inspection requires running your car on a dynamometer to check for stability, so make sure all four tires are at recommended air levels.
Turn your “check engine” light off
An engine-maintenance light is an automatic fail in most states, so don’t even bother driving into the test center if it’s on. Luckily, it’s trivial to turn that annoying dashboard light off. You can either stop at a chain automotive center and ask them to turn it off, or buy a cool code scanner for like 20 bucks. Just make sure you turn the engine light off right before you pull into the testing center. Depending on the issue it’s warning you about, it might not turn back on right away, and you’ll be able to slip by with misfiring spark plugs or something.
Unethical smog test hacks
If you’ve tried all the tips above, and your beloved 1998 Chrysler Sebring still doesn’t pass emissions, the below tips might put you over the edge. (But please don’t actually try any of these things—they are illegal and dangerous, and we are not recommending them.)
Fill your tank with alcohol
Alcohol burns much more completely than gasoline, so theoretically, you could get cleaner test results by draining your gas tank before your smog test and dumping in a gallon of pure alcohol. Opinions vary on whether this is legal, but either way, it’s a bad idea: Alcohol is murder on the rubber seals your engine needs to function, and their decay could lead to oil leaks and all kinds of headaches that will doubtlessly cost more to fix than whatever was causing you to fail your smog test to begin with.
Find a criminal smog center
Sadly, the days of slipping a shady technician $100 for fudging some numbers are over. Computers connected directly to the DMV have made smog-graft way more complicated—but it’s still possible.
Sheisty inspection centers can substitute a “clean” car’s exhaust for yours before transmitting the data to the state, or use a “tach simulator” to trick the smog machine into thinking a vehicle is operating at proper, passing RPM.
(But really, you shouldn’t do business with unethical smog centers. It is no doubt more expensive than a regular smog center, and getting caught could result in a civil penalty of between $150 and $1,000. Smog center owners found guilty can receive fines ranging between $5,000 to $250,000, or even a stint in prison.)