Oh, and one other point, I actually have THREE Dodge Colts, all 1995, and all manufactured in Oct 1994(true). This is true.
One, has 30,000 miles, one has 120,000 miles, and the third has 170,000 miles. The 120,000 mile car was exposed to brutal cold starts in Northern Ontario, and uses slight amount of oil. The engine is still extremely powerful, it always starts instantly, and runs like a top. The 170,000 mile car lived in Southern Ontario, does not use any oil at all, was changed every 3000 miles religiously, was NEVER cleaned, and runs BEAUTIFULLY, EXACTLY THE SAME as the Colt with 30,000 miles. I really cannot tell any difference between any of my Dodge Colts, despite the mileage differences, but the one with 170,000 miles, I repeat, runs BEAUTIFULLY. The 120,000 mile car has NO RUST ANYWHERE, despite long northern winters with VERY LIBERAL USE OF ROAD SALT, because it was oil sprayed annually. The 170,000 mile car, has slight rust, BUT THE REAR BUMPER HAS COMPLETELY RUSTED OFF, and there is ONLY A PLASTIC SHELL, where the bumper used to be. This car was NEVER oil sprayed. The 30,000 mile car has significant rust, was NEVER oil sprayed, and will require some body work, I estimate about $1500 dollars worth. Moral: change your oil, DO AN ANNUAL OIL SPRAY, and DO NOT WORRY, your car will last forever, WITH NO CLEANING WHAT SO EVER. If you really must thought, an MMO treatment should be more than enough. What MMO will do is make the oil EVEN THINNER, so that the FLOW RATE will increase, and the natural cleaning power of the oil will be that much more effective. Please read the following, and exercise due caution:
On the other side of the engine block are those additives which will cleanse your engine, not coat it. Stuff like Bardahl, Rislone and Marvel Mystery Oil claim they can make your engine run quieter and smoother, and reduce oil burning. These are products which contain solvents or detergents such as kerosene, naphthalene, xylene, acetone or isopropanol. If used properly, I suppose these products will strip off your Teflon and zinc protective coatings! But unless you have a really old and abused car, you probably have no need of stripping away sludge and deposits from your engine. Thus, you probably have no need for these wonder cleaners. If you overuse such products you can damage your engine by promoting metal to metal contact.
If you use a synthetic oil, such as Mobil 1, you are advised not to use any engine treatments or additives. Mobil claims that
The use of an engine oil additive is not recommended, either by Mobil or by virtually any vehicle manufacturer. In fact, it may void your new-car warranty.