The gearbox and diff is probably a bit extreme, both are closed systems and completely different designs from the engine environment.
On a car you plan to keep a long time swapping the engine oil after 1000 miles is something I have always done. It's an ounce of prevention and some peace of mind.
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Originally Posted by stormlv
I've even heard people saying the changing the oil too early might be detrimental.
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I've heard lots of things on the internet, just last week I saw a DIY on changing the blinker fluid and muffler bearings on an 83 Corvette.
Yet I still have never seen any conclusive evidence to support such statements. Oil collects dirt, it is also subject to heavy compression and heat. Not only does that assertion fail review on the face of it (here, let me make your lubricant better by adding some dirt) it's kind of hard to hear that old oil is BETTER than new oil and not instantly ask some very logical questions no one can answer.
If it's better to have my old oil say after 5000 miles in my engine than fresh new oil, and in fact to claim new oil is DAMAGING compared to old oil.......why then do we buy new oil? Why is there not a large supply of used oil that enthusiasts are clamoring for?? Tell you what, I'll drain my oil at 5000 miles and you can buy it off me for $20/quart. It's better right?
From the article you linked, I find this part ever more interesting.
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The composition of tribochemical films formed on the surface with the 3000 mile drain interval is similar to that formed with the 12000 mile drain interval as seen before. These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
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So let's consider those other factors shall we? In the old days with conventional oil and engines the real issue with oil was the breakdown of the molecules and the forming of sludge as they did. Oil was changed because it flat
wore out. Synthetic oil (which is actually still made from crude BTW) is designed to resist this breakdown and not to sludge up. This immediately means everyone thinks you can instantly extend oil intervals based on the longevity of the oil. Synthetic's resist breakdown, true, but they still break down. Car's driven to the limits, higher revs, longer heat cycles, etc will increase wear. What happens in reality is we've extended the life of the oil into the realm where we now have to consider the other issue with oils effectiveness; contaminants.
Air is dirty, some places dirtier than others. The air filter stops the big stuff but dirt still gets through, especially if not changed out regularly as well. The oil filter is there to pick up more dirt both from inside the engine and what got past the air filter, but it can only do so much as well. Oil gets through which means there are holes, oil molecules are microscopic.....so are dirt particles. And when an oil filter gets dirty it restricts flow, and under pressure bigger dirt particles will get forced through making bigger holes. Even if we were to stipulate that synthetic oils can resist breakdown for 10, 12, or even 15k miles you must still address the contaminants that reduce it's effectiveness as a lubricant. If you're ever bored, grab some KY and squeeze out a bit in your hand, then dump a tablespoon of sand in there, see how it feels.
In fact, every manual I have ever read states their 'ideal' oil interval and is then immediately followed by the *buts*. Interval will be shorter for vehicles driven in dusty ares, in heavy stop and go traffic, used for short trips, operated in high temperature areas, etc, etc...... Basically the exceptions describe basic everyday life for the vast majority of cars on the road........yet no one ever talks about those. They hear what they want and then just skip off along the yellow brick road.
BTW, a test sample of 3 cars in one location is hardly what I would call scientifically conclusive. LOL