A conventional oven may be koshered for Pesach with libun kal. Since food does not usually touch the walls of the oven, and food on the racks are in pans, the oven itself does not have any real beliot of chametz. Since food sometimes splatters or drips, it is still proper to kosher the oven before Pesach. To do libun kal on an oven, one must first clean the oven from all residue and charred food stuck to the walls and racks of the oven. Once the oven and racks are clean, turn the oven to the highest setting for 40 minutes. This will ensure that all parts of the oven reach the temperature required for libun kal.
In an oven that has “self-clean,” there is no need to clean the oven prior to running the self-clean cycle. One must clean the gasket around the door and the inside face of the door prior to self-cleaning, since those areas are not necessarily cleaned by the cycle. After cleaning those areas, one can run the cycle, and this affects a libun gamur.
The reason a self-cleaning oven is considered libun gamur, even though it does not reach the libun gamur temperature, is because the self-clean cycle takes off more tangible food and stains than an actual libun gamur would. This shows that although the self-cleaning cycle does not reach the same temperatures that libun gamur does, it is more effective than libun gamur because it is done for such an extended amount of time. Therefore, we can also presume that it burns away the absorbed beliot at least as well as libun gamur does. (OU document K-118)
A grill in a park or one that was acquired from a non-Jew requires libun gamur to properly kosher it. Gas grills are difficult to kosher, as most grills are designed to max out at 500-550 degrees Fahrenheit. For a coal grill one can fill the grill with wood or coal and spread it across the grate itself. If the grill is open and one is using lump charcoal, it is possible to achieve the 700 degrees Fahrenheit which is libun gamur according to many poskim. This will kosher the grate of the grill. As it is difficult to fully reach the maximum temperature if one is inexperienced with manipulating the airflow and grate placement on a charcoal grill, one should be wary of koshering a grill. As for the lid and walls of the grill, since there is rarely steam present on a grill, and the food is dry, the walls will not give off forbidden beliot to the food on the grill, even if the walls were never koshered. The only halachic issue would be if the food comes into direct contact with it, which it usually does not. (Rabbi Yitzchok Berkowitz).