Try Seafoam and Marvel Mystery Oil. Prior to an oil change, and when the engine was about a quart low, I'd top it off with Marvel Mystery oil and drive for about a week. The night before I changed my oil, I'd pull the spark plugs, dump Seafoam down each cylinder, and let it soak overnight. The next day, I put the plugs back in, started it up, and let it run for a few minutes before performing the oil change. I did this every 30k miles or so, starting at around 85k miles when the engine first showed signs of excessive oil consumption. My 2.4 would always use about a quart between oil changes, so when it was down over a quart at 50% oil-life remaining, I knew come the next oil change it was time to do it again. You wouldn't believe how dirty the oil filter can get after this procedure.
New pistons and rings WILL fix the problem, but the cleaning does help.
Good luck!