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Driving a well-maintained, repeatedly serviced car is one of the best methodology of passing an emissions examine, however what are ya, some form of sq.? When you don’t have a more recent automotive, try the ideas beneath to try to squeeze your beater below the smog-check wire. And if that doesn’t work, don’t use the less-than-ethical, most likely unlawful smog-test cheats on the finish of the article.

Moral Smog Suggestions

Take a look at with a sizzling automotive

Working your engine earlier than the check might be probably the most helpful methodology of maximizing the probabilities of passing. A warmer engine means extra gas is burning, so much less gunk is popping out of the tailpipe. Earlier than you pull into the testing heart, drive round, ideally at freeway speeds. Motortrend examined this concept by working a automotive at elevated RPM and heavy throttle and located “Emissions decreased throughout. Even our O2 output decreased.”

Attempt a gas additive

Gas components are designed to extend effectivity by cleansing carbon residue out of your automotive’s engine and exhaust path—a extra environment friendly engine means decrease emissions and hopefully a handed smog check. Comply with the directions on the package deal earlier than your smog check. A “normal” fuel additive like Chevron’s Techron ought to assist, or you possibly can go along with one thing particular, like CRC-Guaranteed Emissions Formula.

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Use low octane fuel

Don’t fill up on super-premium before your smog test. Go for that cheaper, low-octane stuff we all put in our Kias. It burns faster than higher octane fuel and thus produces fewer emissions—according to, anyway.

Make sure your oil is fresh

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 manufacturer’s recommended oil changes, change it. The fumes from your sinfully filthy oil compartment can infect your engine and come out in the emissions, according to

Make sure your tires are properly inflated

Low tire pressure or uneven inflation of tires can negatively affect how your engine is running and thus its emissions. According to, many states require a dynamometer test, and under-inflated tires will cause your engine to work harder to achieve the revolutions required by the test.

Turn your check engine light off

While a lighted “check engine” indicator is an auto-fail for emission checks, the often repeated idea that you can turn it off right before a test and hope to “squeak by” is controversial. (Some sources say it could work. Some say it wouldn’t.) Instead, go with the tried-and-true: If your check engine light is on, take your car to a mechanic and get it repaired.

If you’ve tried all these tips and your beloved 1998 Chrysler Sebring still doesn’t pass the test, the below unethical tips might put you over the edge (but please don’t actually try any of these things—they are illegal and dangerous.)

Unethical Smog Tips

Fill your tank with rubbing alcohol

According to the US Department of Energy, 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 probably a bad idea:  According to car industry trade groups, even gas that’s only 15 percent alcohol hasn’t been tested enough to know how whether and how it would damage your car.

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’s have made smog-graft way more complicated, but it’s still possible. Shady 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 for consumers and a fine for station owners ranging between $5,000 to $250,000, or even a stint in prison.)

This article was originally published on Sept. 16, 2021 and was updated on Sept. 19, 2021 to correct factual errors.

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