To eliminate routine oil drains and to keep the engine in new condition as long as possible requires that the oil is never allowed to get dirty and enough new oil is added. Motor Guard has always recommended that their filters be changed every 2,000 miles. This is over kill for most cars but it is always best to err on the safe side. If all engines were the same and all driving conditions were the same it would make it a lot easier for me. As a rule of thumb if the oil looks like new and the viscosity feels like it did when it was new you are changing the filter often enough. The full flow filter doesnt count. It is just a strainer. There is virtually nothing in the oil large enough to be filtered out by the full flow filter unless you are putting a lot of stress on the engine such as off roading or racing. When Motor Guard and Frantz made their recommendations years ago engines were a lot dirtier than they are now. I was looking at some old testimonial letters from the Marion County, Oregon Sheriffs Department that use the Frantz oil filters on their patrol cars They change the full flow filters every year and the Frantz filters every 2,000 to 3,000 miles. That sounds about right for a high performance 8 cylinder. They also do a lot of idling. That had been working for them for 20 years when the letter was written. 2,000 miles will cover about any condition. They dont drain oil on the patrol cars.
I would think that a 6 cylinder would do fine at 3,000 mile filter change intervals for the bypass and the full flow filter changed about every 15,000 mi. With no oil drains unless you get a leaky head gasket. Fuel contamination is rare these days.
If the oil starts looking like dark honey instead of lite honey I know its time to change the filter. I drive my Camry about 40 miles a day 6 days a week. About every 4,000 miles filter change interval. It has no full flow filter. Some of the old timers never changed the full flow filter because the bypass filter keeps it clean by removing the contamination before it can bunch up into larger globs that the full flow filter or change it every couple of years.
There are some reusable full flow filters that you could just install and forget except to check them for leaks and check them for tightness. They can loosen up when they are on there a long time.
If I was going to do a full oil change like Fasty says I probably would not change the filters until the 25,000 miles. Then I would change the filters and the oil. I would keep an eye on the dipstick I might change the TP half way thru.
I was reading a 1937 Studebaker book that said not to drain the oil but change the bypass filter when the oil looks dirty on the dipstick. That will work except it is always better to change the filter before the oil gets dirty. The 1937 Studebaker had a lot better filter than the stuff they put on the new cars. I think they were optional equipment in those days. They were optional equipment on my 1938 Chevy. Frantz got their start by converting the old bypass filters to submicronic. Slide a roll of tp into a steel container and it fit the old housing. When they quit making good elements for the old housing it didnt matter if you had a Frantz conversion.
Ralph
