Another thing i have noticed if you let them grease (Diesel/Oil) your car from underneath, in time sand starts accumuating under your car. And for those who live in a humid climate like Karachi, the sand absorbs the moisture and becomes dirt, which brecomes a breeding ground for RUST !!
So please do not apply oil/diesel/grease at the car wash.. If you have any noises coming , better to identify the specific area and apply grease directly there.