This is what I do now...
Change the oil every 5000 miles (this is the fleet standard) or spring and fall which ever is more frequent. If the oil is really dirty do a complete change and run it only until it gets black then drain and refill with clean oil.
I've started using is the 15w-40 diesel spec oil that comes in the gallon jugs. Delo 400, Delvac and Rotella are a some brands, but I think they are pretty similar with regard to what they do. A gallon costs about $10 US dollars. According to the info I've read (almost all on the internet) is that the most recent specs for oil marketed for gasoline engines have reduced the anti-wear additives that protect against metal on metal contact (like what happens on camshafts and on cold start-up before the oil system pressurizes) because these additives can compromise the function of the catalytic converter over time. Fewer antiwear additives mean greater potential for wear on high mileage engines where the wear may beginning to get outside the design tolerances. The oils marketed for diesels reportedly have more of these than the non-deisel oils because of the extended drain intervals for diesel engines. The other advantage is that the base oil (the 15w number) has a greater viscosity that the 10w oil originally recommended. The greater viscosity should help build a thicker oil film where there has been bearing wear on high mileage engines.
For cold winters in an old Tercel I'd use 10w40 or 15w40 (unless it was a low mileage engine that came with a different viscocity recommendation). For hot 40C summers I'd run 15w40 or 20w50. 10w40 was too thin for my previous engine with 150,000 or so miles and reving it hard
- I won't use anything but 15w40 or 20w50 or thicker on high mileage engines.
Those are my superstistious oil opinions (and you know what they're like!) - but I just bought a Toyota PU with 207,000 miles on it and the engine is absolutely clean inside
and the previous owner (from new) said he just used the cheapest oil and changed it often - "every season".
New Toyota's are apparently filled with synthetic from the factory.
I use the smallest and cheapest oil filter and change it with every oil change. The smaller filter will allow the oil pump to repressurize the oiling system more quickly on start up and you're going to change it every oil change anyway (so more fillter area isn't that big a deal).
Filters are made with an "antidrain-back valve that is supposed to keep the oil filter full when the engine is not running so that the oil system repressurizes quickly on restart. The only reason I would pay more for a filter is if it had a better antidrain-back valve. (this is an issue on the 3AC because the filter is tipped on its side) Fram and Penzoil filters always seem to drainback, WIX/NAPA filters may be better.
I drain the oil warm not hot because I don't like to burn myself.
While it's draining I write the mileage the car is at on the end of the new filter with a black permanent marker and and fill it with fresh oil. You will find that the oil level in the filter will drop as it soaks through the filter so I top it up. I do this so that the oil system will repressurize more quickly on re-start. A little of the oil will spill on the side of the engine when you put on the filter which is why I have a rag handy.
Sometimes I will leave the drain out when beginning to add the new oil, it will push out some dirty oil and I put the plug in when the clean oil starts to come out.
Then I crank the engine without starting it until the oil light goes out, then I start it.
Hope this helps!
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