Hello! Would like to make an oil change, would also use the engine clean from Liqui Moly to solve some deposits. Is the engine clean recommended ?? Have an Audi 100 2,3E Type44 NF engine Bj.90. This is basically an old engine from the 80s. Can one drive there problemless full synthetic oil (5W40) ?? Or better partial synthetic oil (10W40) How does e.g. 5W40 with old gasket and oil consumption ?? Does with 15W40 already need a lot of oil (had this time Ber MfG) MfG