Nissan tech explained that I have sludge in my

There are no hard and fast rules for curing an engine of sludge buildup. If it's really bad, flushing the engine might be the only cure.

If you do decide to do an oil flush, first drain your engine of all it's oil, but leave the old oil filter in place. Next fill it up with flushing oil and run it at a fast idle for about 20 minutes. Finally, drain all this off (and marvel at the **** that comes out with it), replace the oil filter, refill with a good synthetic oil and voila! Clean engine

Desludging an engine is a waste of money you need a new engine. Only use synthetic oil.