Leather,

It all depends on how the engine is used. If the engine is run until it gets hot almost every time it is started, 5000 miles will be sufficient for Dino oil.

If the engine is used where it rarely gets hot, then it should be changed by length of time not miles. So every 3 months will be OK.

For Synthetic, oil the above can be doubled.

But a flat "every 3000 miles" is ridiculous with no account of how the engine is used or what type of oil is used.

P E H