 I have had 5 Hyundai's in my family in the past 10 years. All experienced issues with rusting underside, and around all the brakes.  The most recent 2012 Elantra went in with a value tap, and they replaced the engine. All the other models are known to have engine issues, but they were in denial on this model. They also pointed out the accelerated rust on the undercarriage. Speaking to other Hyundai/Kia owners, there is an obvious pattern where some cars had this rust issue, others did not. My local mechanic said the underside looked like a car that is frequently parked over the grass, but this car was always on pavement. There is something wrong with their undercoating or lack of in manufacturing. The dealer wanted to charge to fix it.  When we got the car back, with the new engine....we immediately traded it in for another new car...not a Hyundai this time.Update 9/2017. Many of our friends with Hyundai's says dealerships trying to blame owners for the excessive rust issues on the undercarriage. Said its our fault when its likely lack of rustproofing or bad/cheap metal used in body. FYI:  Car always parked on pavement. Also, everyone I know also had the engine replaced.  They traded cars in for other brands.