Some people believe additives break down over time, and blowby leads to sludge based on mileage. I know some people, including me, will shudder when I tell you I haven't pulled the drain plug on my '88 Grand Caravan in over 8 years. I drive it every day at least 20 miles, and use it to pull a tandem axle enclosed trailer that weighs twice as much as the van. I don't need the trailer brakes, I can't get more than 75 mph down a steep hill with it because of the wind resistance, and the engine runs warm when doing it, but that engine has over 379,000 miles on it. That lack of oil changes is not neglect. That is abuse, and obviously I'm not recommending anyone else do that to their engine.
The point is it shows what today's oils are capable of. This is the only vehicle I own that I do this to, partly as a demonstration to my students. I have to add a quart about every 1,000 miles, so it is still getting the detergents, anti-corrosion additives, and anti-foaming agents that you get with an oil change. I use the cheapest farm supply store oil I can find which is actually produced by a well-known national company. I also replace the filter once every two years.
There are some other engines out there that are very sensitive to oil change intervals. Toyota had one of them in their cars in the '80s. To my knowledge yours is not one of them today. Unless someone has a reason to tell you otherwise, I wouldn't be too concerned with the three months if you drive the truck regularly. Pay more attention to the 3,000 miles. If you do a lot of highway driving, the miles add up faster but the additives don't wear out any faster so you might go further between oil changes but I wouldn't extend it too much because deposits will still be building up that are removed when the oil is drained out.
Those recommended intervals are partially based on the life expectancy of the additives in the oil and partly on preventing the manufacturer from having to pay for engine repairs under warranty. If they found their engines would hold up with 4,000 mile oil changes, they aren't going to recommend you wait that long. They have a safety margin built in, so they would go with the 3,000 recommendation. Some manufacturers also insist you have the oil changed at their dealerships to prove for warranty purposes that the oil was changed on time. They do not accept receipts from other shops. That is their loop hole for getting out of paying for repairs under warranty. Ford and GM are very good about skirting their responsibilities. I've never heard that about Toyota but if that becomes an issue, you might want to check with the service department at the dealership. You can also speak with the person who takes care of the warranty paperwork. Ask them what proof of oil changes is required in the event warranty engine repairs are needed.
Ford used to recommend 7,500 mile oil changes on some of their smaller cars. The sole purpose of that recommendation was to show how much lower their annual maintenance cost was compared to other car brands. It wasn't until after you bought the car that you found out it was almost impossible to meet the conditions for that extended interval. Anything that resulted in "severe" driving conditions meant it reverted back to 3,000 mile intervals. Severe conditions included extended city driving and extended highway driving. Basically everyday normal driving was considered "severe".
Monday, July 11th, 2011 AT 7:19 PM