Most modern engines use what are called PC seals on the intake and exhaust. They fit tight on the valve and the guide preventing almost any oil from getting to the guide.
Example You would think valve guides would need oiling but they seen to work fine with almost nothing.
The advantage in PC seals are, they stop what amounts to a vacuum leak past the guides on the intakes, and prevent exhaust gasses from getting past the guides on the exhaust, and entering the engine.
