Trouble? - Is this normal?

[Mr 5 0]

Perhaps I'm missing something here (it happens) but it sounds as if you're using about one quart of oil every 2500 miles.
That is excellent oil milage on an older 5.0 Mustang - chip, timing and all.

I've owned my '90 LX since it was new (110,000 miles, now) and I've used about a quart every 1500 miles since day one...never any more or less. FYI: I change oil and filter every 2,000 miles and use 'regular' 10-30.

2500 miles per quart of oil is no problem.