I've noticed that after I did my last oil change (5W30 Mobil1 Syn) my oil pressure light has been flickering more at startup. It's not coming on while driving but it is on noticeably longer than it used to be, somtimes as long as a second. Any ideas?

i noticed the same thing on mine i use 10-40

Check the oil level on the dipstick.

I notice mine does that when I'm about a 1/4qt low.

It's possible that the cause is the antidrainback valve in your oil filter. If this leaks, and many do, the oil filter is empty at startup and takes a while to fill before pressure forces oil to the oil passages. I have used a SuperTech (WalMart) since my first oil change and have not had the problem. I have no idea which brands are better, and the filters tend to come from different manufacturers regardless of the name on the box.

I'm pretty sure if you let them sit over night, which is when I typically see it, all the oil has drained back?

Not sure how long that antidrainback valve works.

That valve most likely has nothing to do with the light. When that happens to my car, I'm 1/4 low~ish every time.

I noticed mine happening 1/8-1/4 quart low also. I never worried about it, since it never came on when I was driving. I'm glad to hear that I wasn't the only one with the OPL. It only happened when the car sat long enough to cool and bring down the temperature gauge.

Like all you guys have mentioned, it also only seems to happen to me when the engine is cold and the oil has drained back.