In my mechanic days we used a standard of 100 hours between oil changes. These were 3, 4, 6, 8 and 16 cylinder diesels, which if they weren't at idle they were at full throttle. During some operations and on several applications, that meant changing oil every 4-5 days. That was 4 gallons or so on the small engines and almost 10 gallons on the big ones. These all used dino oil.
On the radial, multi stage compressor (which was coupled to a 4-53 Detroit) we used synthetic due to the higher heat generated by the air compression, and it was changed at 100 hour intervals as well.
I only recall one oil related failure, and that was caused by a cracked oil line, which sprayed oil all over the engine room. I have seen engines toasted due to no service/oil changes, but have never seen one damaged by excessive oil changes.
I did just think of one possible scenario - constant oil changes wearing out the drain plug, not replacing when worn and the plug falling out, leaving a trail of nice new oil down the highway.
73 280 SEL 4.5
[This message has been edited by MikeTangas (edited 10-31-2000).]