I have had several Chevys-both truck and cars- some with oil filters and some without. The vehicles had either 216 c.i. or 235 engines. In the past oil filters were an extra cost option but in later years most 235 cars and trucks had the filters installed at the factory. On the cars or trucks without filters I always changed the oil every 1000 miles-of course that was before all this modern oil was invented. Even with filters I change both oil and filters after 3000 miles and have never had a problem-getting well over 100K miles out of all my engines. I would drive my truck and just change the oil every 1000 miles- using a best grade 30 wt. oil!
