I have a 1995 Buick Skylark (V-6). I noticed if I put in a half quart extra at an oil change I no longer hear the valves tapping on start-up. Is this normal? I assume it’s due to wear but I thought if you overfill the oil you risk foaming.
Without a check valve start-up rattling is common on many engines. The level of the oil would possibly lessen the oil pumps draining down and therefore lessen the tapping. Is your filter installed horizontally or vertically?
Try putting in a top of the line or dealer supplied oil filter. Sometimes the filter has a check valve in it that prevents the oil from draining back from the engine after it is stopped. If the oil drains back from the hydraulic lifters they clatter until they pump up. I don’t know that any real harm is done, but it sounds bad.
An extra half quart of oil is no problem whatsoever. And quietness is always better than extra noise. Worry no more.
A half quart over will hurt nothing and not cause any foaming.
I also think that any tappet noise going away is a sheer coincidence.
A half quart, or even a full quart over, does not have any affect on lifter operation at all.
You have a faulty lifter(s) assuming the noise is actually related to the lifters.
Vertical such that it does not drain back at shut off. I should also mention compression is great for 89,000 city miles, no oil consumption.
An extra half quart is not likely to cause a problem, but I would worry about a full quart extra, that could be very bad.
Make sure you have the right oil filter for the car. Even if it is the right one, you may want to try a different brand. Many oil filters have valves that prevent the oil draining back to the sump so it is available on start up. What you are doing is just getting that oil up there a little faster.