I replaced all the ventilation hoses, had the oil changed with 10w30, and drove it the first day, all seemed well. The next day I drove the 34 miles to work, and the oil light came back, flickering at idle. 2 days later (I am a truck driver, so the car sits for days at a time while I'm on the road,) I pulled the dipstick, oil was full, so I drove it back home, in stop and go traffic no less, and no oil light. ran like a champ. The next morning, I drove back to work, when I exited the highway, breathed a sigh of relief, no oil light. Pulled into the employee parking lot a few blocks away, and dammit, there it was, flickering again, taunting me.
This car makes no unusual noises, it runs like a top. I bought it 8 months ago, put $1200 worth of brake and chassis work into it, and the oil was black as coal. I've had the oil changed 3 times with 5w20, the odometer is 160,000, it was at 154000 when I bought it. there is an oil leak on the bottom half of the motor, nothing substantial, I add maybe half a quart every 2 weeks.
what's my next step from here?
Above you've posted that you had the oil changed with 10w-30 & your engine is specified to use 5w-20. You seem to be located in the north east, so this time of year thats cold country & your engines top end cams sure would appreciate a 5W lube, so that it gets some right away after a cold start.
If the engine is sludged up some, such that the top end oil returns are clogged up & holding more oil than they should, or the thicker than specified 30wt might be taking longer to drain back to the oil sump, causing it to run low after a highway run because a lot of it is still in the top end. If the top end is holding more oil than it should, that oil can be whipped into a froth/areated by the cams & that, along with a slow drainback to the crankcase, can cause the sump to run low & if the oil returning to the sump is areated, the oil pump sure won't like trying to pressurize it. So, make sure your using the specified viscosity & service grade crankcase lube.
If you used other than the specified Motorcraft oil filter, put that on your flickering oil light suspect list too, as I've also had other oil filters cause a flickering oil light at idle, or start up rattle.
More thoughts for consideration, let us know how it goes.