I just changed my oil last weekend (Valv. synthetic blend) with a new Mann filter), and now I have a leak. There has always been a small small leak, but now it is much more. I would guess maybe about a few tablespoons overnight. There are drips from the frame right in the middle of the engine when looking from below. I have checked the filter and drain plug. Both are tight and no oil around them. The car has about 160k miles. I have had this car since 100K. It is my sixth brick. I have checked my oil level and it is OK. Where could it be coming from? Any ideas? Thanks in advance!

If it increased right after an oil change, are you sure that it is not just some leftover spillage from changing the filter? They can dump a lot of oil, and it can take a while to drip. Did you change the viscosity of the oil you were using? If you went to a thicker oil, you would increase your oil pressure. More pressure, faster leaks. I do not believe the Valvoline blend by itself would cause it to suddenly leak, unless it was a viscosity increase. Their 'high mileage oil' is slightly thicker than the regular stuff of the same grade.
The small amount of PAO or groupIII syn they use would take a while to clean a seal to the point of increasing a leak. IF it is none of the above you would have to start looking for the regular suspects. Has the flame trap been serviced?
Clean the engine and look at all the gasket and seal locations. Oil filler cap, valve cover, cam and crank front and rear, oil pan, distrib base,etc.

first off synthetic will make your leak faster., also with you getting near the 200k you might want to try 20/50 if your not already useing it. Check the top of the engine for where the oil is comming, if its dripping down your should see a line of oil comming from where ever it's comiing, minus the fact it could be comming from the oil pan gasket.