Originally Posted by mahout

Honda does but you might be alarmed at Honda engineers who don't follow the7500 mile oill change and 15,000 milefilter changes. Most think 5000 miles is long enough for both. You might want to consider why 'severe service' intervals are given. Some of us think every day driving constitutes severe service.
For those of us who have access to dynomometers and engine teardowns we recognize that marketing often takes presidence over engineering. its the reason Dilbert is so popular with engneers.
Granted most of the teardowns and dyno tests are done on engines that see heavy duty service so the oil analyses are are more 'at the limits' of service. But a few have been on regular oil changes and the longer you run between oil/filter changes and the smaller the filter the worst the contamination.
And yes if you run too short an interval lubrication suffers. oil has to break-in too. to get the right viiscosity mix. An old story about Bunky Knudsen, who became GMpresident, was that his first project was to find out why the engines failing initial startup did so, a left-handed monkey wrench project. (way back new guys in the shop had to get an experienced mechanic a 'left-hand wrench so the job could be done right, offering much amusement to experienced mechanics)
Only in Bunky's case he found that almost all the failed engines occurred within 50 miles of the fresh oil fill. He also found that the viscosity of the oil had to be reduced by about 5Z% before the engine was well lubricated and that penetration of oil films betwwen close tolerance parts was essential. NASCAR troops found the same by running oil in their street cars for a few miles before putting in the race cars. More of old days stuff.
The real reason nowdays for reasonable oil/filter changes in contamination as much as oil shear strength reduction. Oil in order to lubricate engines must provide excellent shear strength, meaning when the oil is stretched out in thin films, as happens between two counter-rotating parts,must remain in a continuous sheet rather than separating into ribbons, thus allowing metal to metal contact. It most often doesn't result in ddisintegration of metal but does accelerate wear. And why oil analyses are carefully monitored for imetal content. The loss in shear strength is noticeable the longer you run, especially in high rpm engines.If you don;'t run over 4000 rpm it probably doesn't matter.
And, yes, sometimes I feel like I do change oil for a living.
PS the only long term testng reports I've read are those from Mobil where they tested mobil 1 for distances up to 25,000 miles but I tended to think their service conditions were a might tame. Like a lot of others I tend to 'err' on the side of 5000 mile intervals for synthetics and 3000 miles for napthenic based oils simply because, even using synthetics, its such cheap insurance..
Peace.