'97 Buick LeSabre

'97 Buick LeSabre, V6 3.8 liter engine was fluctuating between 55 and 70 psi oil pressure @ 70 - 75 mph highway speed. Is this o.k.? If not, what could be wrong ??

Yes it is OK! You are probably seeing fluxuation due to oil drain back. At those speeds the engine pumps a lot of oil and it takes a little while to drain back to the pan. 55 psi is fine and the fluxuation is normal.

This can also be caused by too much oil, causing aeration and consequent pressure fluxuations, a bad sending unit has also been known to cause this Ordinarily the oil pickup is constantly submerged, so these other issues should also be looked at.