Many people I know like to use 5k and 7k as safe intervals to change the oil. What are the chances that Mobil 1 would leave deposits at short intervals like this? Is it even worth using synthetic for 5-7k mile oil changes? My thinking is your probably safe up to 10k with Mobil 1 or any oil that shows a strong TBN. I'm assuming that if your TBN is 4> your engine will stay clean. But Mobil 1 does have lower ester content compared to Redline and Amsoil.