I was at a generally knowledgeable and respectable oil change place a couple of days ago getting my oil changed. They mentioned a special they were running on getting the “sludge” out of my engine and I should do this every two or three oil changes. It would only take 10 to 15 minutes. Well, me having just a bit of knowledge on the subject, asked them what they were using to help get rid of the “sludge” in my engine. The product was in a gallon container, the serviceman said it would take the whole gallon and this product was recommended by their company. I looked at the ingredients, the first ingredient was ethylene glycol. I DID NOT have them get the “sludge” out of my engine. Here is an article explaining the effects of ethylene glycol in the crank case.
This basic knowledge may save you thousands of dollars. If you have sludge issues in your engine, there are ways to remove it safely without harming your engine.
The best way is to not have the problem in the first place. Use a quality oil with a good additive package and don’t try to overextend the life of your oil.