1994 Toyota 4Runner

My girl friend has a 94 four runner that seems to have a cooling problem. When she drives it more than around 10 miles it starts to smell really hot. It smells alot like burning oil which makes since because she is either leaking oil or she is burning it up. I have looked for leaks but like any older car there is oil all over the place but there doesnt seem to be a place that there is a big leak. It is also hard to say if it is overheating or not because once the car is warmed up to running temp the temp gage never moves