Two days I began to hear a knocking noise on my 2012 KIA Optima. Drove it instantly back home and had it towed. The next day I called the KIA lot and was told it was not there. Finally after going back and forth all day, they realized they had it, but it was on the MAZDA side. Now though I encountered bad customer service at the car lot, my issue is NOT with the lot. It is 100% with KIA. At 51,000 miles I am told I need a new engine. Even though we did regular oil changes, some by my husband, some through Walmart I have to pay for this. Due to SLUDGE. Sludge? Is it my fault this car accumulated sludge? KIA guarantees a 100,000 mile warranty, yet it is indeed false. This is day 3. I am still without car. KIA will not honor their warranty. This could be someone's mother, one of the elderly, or one of our armed forces. My husband by the way IS a vet. My son is an Airman. KIA should be ashamed. A fan of LeBron James, I can not believe he endorsed this car. I hope my story helps someone from making the horrible mistake of buying a KIA like I did.