There seem to be different "forms" of engine flushes. There are high-speed/pressurized systems that "flush" out the engine, not exactly sure how. Then we have other techniques such as emptying one quart of oil from the crankcase, add 1 quart of kerosene, and then let the engine idle for 5-10 minutes. Then another similar, is the "seafoam" treatment, in which you add 1 fl. oz. of "seafoam engine treatment" per every quart of oil your crankcase holds; drive the car safely (don't hammer on the gas pedal, or doing any sporadic driving out of the norm) drive the vehicle to your oil change location, and get your lube oil and filter change done, with the vehicle as hot as possible. Keep the engine idled in the parking lot until they can service you. The Seafoam (which is a 100 percent petroleum product), IPA, and some other cleaning agents works by cleaning up the internals of the engine, which is less harsh than these "pressurized" systems that some of these quick lube places perform. So anyway, get the oil changed, and after it's done, I always like to look under the hood, check the oil levels, and make sure everything is to spec, and then add more seafoam (this is post-oil change), same as the pre-oil change, one oz. of seafoam per every quart of oil. Every gasoline fill up, you want to monitor the level and color of your oil (which is why I also mentioned to check the color after the oil change, while in their parking lot). When the oil gets dark, it's time to change it. But, don't drive anymore than 3000 miles on this "seafoamed" oil. Depending on how much sludge you had built up, you may not even experience black oil at the dipstick, but don't go anymore than 3000 miles on this oil. After this, just get the lube, oil, filter, changed as normal. Perhaps upgrade to a synthetic, or even a synthetic blend for added protection and engine longevity (some oil advertisements even claim an increase in MPG using synthetic. who knows, though). Seafoam is s straight 100 percent petroleum product, but also contains other additives to help clean out your crankcase and other "innards". So it won't "thin out" your oil at all. The thing you've got to be careful for, is older engines, or those with excess sludge, having that sludge get freed up, it's no good driving on sludged up/softened oil. Which is why I recommend the initial "flush" then the second/post "treatment" to soak up the remaining sludge that may be left behind. Last of all? Don't skimp on your oil. Demand the best, do your own research on oil and get the best for your vehicle, if you want your vehicle to last.