QUOTE (ZZman @ Mar 5 2009, 06:59 AM)
It depends on the additive and what it claims to do. Many of the cleaning additives do work.
There are many dedicated Seafoam, Marvel Mystery Oil, Auto-RX users etc....out there.[/b]
I know. It can be an inflammatory topic because some/many users have used these product for years and had what they consider to be great success wth engine cleaning oil additive products. This is the only category of oil additives that can be debated as being actually beneficial. At least no one is attempting to justify Slick 50 or STP engine treatment, I'm thankful for that.
None of those detergent products are as good as an oil change with fully synthetic and staying with synthetic. Does anyone disagree? If so, my points on this follow.
Unless you've already got a "broken" engine and want to swell up some seals and let your pistons grind off some carbon that is sticking a ring or two and your lifters aren't getting enough oil due to sludge, there is no good reason in my opinion to put that stuff in your crank case.
Those products are cheaper than synthetic and make a person feel as though they are doing something more than just changing their oil with conventional motor oil. I assume people use those products because they know conventional oils gum up, varnish, and sludge their motors. Those products also remove the oil metal barrier and allow the metal to grind off some carbon and those products swell the seals and turn them to jelly eventually.
If you want to do more than just change your oil, switch to synthetic.