I do not have the engine chemistry that many of you have but I do maintain the best I can. In 2009 I bought a Dodge pickup for a job truck with 102,000 miles on it. It had a 4.7L engine, that I had no knowledge of. I took it to my local garage for an oil change and service. Tony told me all was well other than sludge build up and he put a new pvc in it. I took it to my farm and added the required amount of Seafoam and drove it fo 3000 miles. Took it back for service and Tony asked me what I did since the engine was much cleaner. I drove it to 187,00 miles before getting broadsided.