If you are using a high quality oil then the need for cleaning is not very likely if you carry out the recommended oil changes.
However if it worries you; drain the oil and replace the filter, use a cheaper brand of oil and run the engine to clear out the oil-ways and the like, use at moderate speeds for lets say 200 miles then drain, replace the filter and refill with your usual higher quality branded oil.
I would do this especially if the engine was turbo charged as this helps lengthen the life of the turbo.
Never run a turbo'd engine at high speed with a low quality oil.
Never add a cleaning agent to the oil. Read the article below on what can happen. As for fuel injector cleaners, Chevron Techron is the best one out there.
"Snake oil" is snake oil. Doesn't matter which one you use. NONE OF THEM are really going to do GREAT things for your engine.
The people who designed your car's engine have HUNDREDS OF YEARS of combined experience in automotive design and maintenance. If THEY don't recommend an oil additive for your engine then WHY should you use one at all? Just change your oil and filters at the recommended intervals, and that's all the "cleaning" your engine should ever need.
Never use additives. Ever!
I have an 05 grand prix with 166k with original plugs and wires, my car gets roughly 18ish mpg probably due to it needing new plugs but my question is what oil additive works best cleaning the internal parts of the engine, such as injecters, and cleaning up carbon deposit, I figured I'd give my car an oil change once I do the plugs. I heard good things about Marvil Mystery Oil but what's your opinions
