bought the car brand new and in 2001 olds Alero 3.4 ltr V6 kept hearing a knocking noise, cold starts it didn't wont to start up took it to the dealership they said they found a substance in the engine they thought someone introduced the substance. then they did a oil analysis and it was just oil then they began to point the finger at me saying I didn't get enough oil changes. True I didn't get all of my oil changes exactly when scheduled but I did get them. In the past I had a 87 olds omega and when the oil got old it would burn and get black and thin, not thick and brown. GM has a defect they just don't want to replace all the engines that are going to have trouble because of this.