1989 Ford F-150

Engine Mechanical problem
1989 Ford F150 6 cyl Four Wheel Drive Automatic 68000 miles

in my truck when I remove the oil fill cap there is all this mustard green looking stuff all on the inside of the cap and around the neck of the oil fill hole and im puzzled about what it is?
March 13, 2009.

Sounds like you are getting a antifreeze in with the oil.

I would be checking for a blown headgasket/cracked block/ or cracked head.

If its not that I would suspect an issue with cracked intake manifold or a bad gasket on the intake manifold.

Mar 14, 2009.
It's only normal condensation - start to worry if it shows up on dipstick.

Mar 15, 2009.
One way to see what it is if your daring, taste it. Sweet its antifreeze. If it tastes like exhaust smells and gas its normal condensation.

Mar 15, 2009.