Seems to me the best time to change your oil is at 1 mile, worst time is never again. Somewhere between 1 and infinity there is the optimum time to change your oil given the tradeoff between time+cost and engine protection. It is a surety that the manufacturer, dealers, and marketing are not recommending the optimum oil change cycle that is in YOUR best interest. Their best interest includes things such as:
What do our market competitors recommend? - If Chevy recommend the Suburban needed changes every 15,000, and Ford recommended the Expedition every 3,000, most midwits would conclude the Expedition has a crappy motor and the Suburban must have a much better motor since its oil can last much longer without a change.
For every 1000 miles less we recommend how does that increased burden affect our sales? - Related to the above statement but more of an evaluation on its own. People are lazy and would prefer to have a vehicle that never needed an oil change. Any # of changes more than 0 is worse.
What's the minimum number of changes required to make sure the increased warranty service due to lack of oil changes is less than the lack of sales due to customer perception that frequent changes = crappy motor? etc etc
I don't think anyone knows the exact optimum time given the tradeoffs. Blackstone reports that your oil is good enough after XXXX miles, but it still isn't as good as day 1. If you leased the car for 3 years and are going to trade it in is a different calculation than you bought a 10 year extended warranty and are going to drive it into the ground. For me, for now, 4k sounds about right. It's a boosted engine, I'm going to keep it for as long as I can, and I couldn't care less about "wasting" oil. If I add an intake, intercooler, and tune, probably 3k. Depends on how much fun it is after that and how much I drive like an ass. Why not? Or, if you change your oil more often than you take your wife out to dinner, you should probably take your wife out to dinner more.
) left in the oil.
