The instructions are very easy to follow: Simply change the oil as you would normally. Any “confusion” is just myth. You can switch from conventional motor oil to Mobil 1™ synthetic oil (and back again, if you want) without following any special procedures.
However if your vehicle has a higher-mileage engine that has never used synthetic motor oil, or one that has been poorly maintained with infrequent oil changes, we recommend easing into extended drains to allow Mobil 1 to clean up the engine. In these cases you should still follow the same basic oil-change procedures (drain the old oil, remove the old oil filter, put in new Mobil 1 motor oil and put on a new oil filter). Follow your OEM’s recommended maintenance practices regarding oil changes, but you should follow more frequent (one or two non-extended drain) oil changes when first switching to synthetic oil.
The reasoning behind these shortened oil drain intervals is that a high-mileage engine, or one that has had a lack of maintenance including infrequent oil changes, will likely have a considerable buildup of sludge and deposits. Mobil 1 motor oil will help clean the engine as you drive, but it will have to work much harder in a very “dirty” engine, and so it is best to change the oil more frequently for those first several thousand miles. After that, you can rest assured that Mobil 1 synthetic oil is continuing to keep your engine running clean and well lubricated for mile after mile.