shows low oil after driving on 1996 Isuzu Hombre

Had engine replace in my 1996 Isuzu Hombre in April 2009 and have had regular oil changes since. In the last month I have started having the truck show that my oil is low after I have driven say 35 to 50 miles (highway) and when I stop the truck sounds like a thrashing machine,which I figure may be the lifters but when I check the oil it shows that I am fine on oil and the oil is not burned or anything so my question is I was told that I may need to replace some kind of oil/fuel sensor,is this what I need and if so what exacatly called.

Asked by for the 1996 Isuzu Hombre
I know of no oil/fuel sensor. Clearly a new or rebuilt engine should run perfectly for many, many miles, take it back to the shop that put in the engine, it is their problem.
1 more answer
The issue you describe is caused by a faulty oil sending unit. You can change it yourself very easily. It can be purchased online for as little as $10, and generally, the auto parts stores charge around $30.