[2002Altima]

Using a drop in K&N air filter does not void the warranty.

Modifications to the factory set up may cause your dealer to question your work. Therefore, the people who attach the cone filter usually take it off and put it back to factory looking if they are going to take the car in for warranty work.

 

[2002Altima]

I guess it depends on your dealer. Courtesy Nissan here in Dallas really supports modifications and even sells some altimas from their showroom with K&N filters, new exhaust, different wheels, etc. So does Mossy in Oceanside, Calif. I know they wouldn't have a problem with it.

If you take your car in for an oil change, they aren't doing warranty work, so they aren't going to say anything.

But if your car doesn't start and you have to have it towed to the dealership for warranty work, I would put everything back to stock before they take the car and blame the modifications for being the reason that there is a problem.