Could be climate and different type of oil used. 5K is my standard change interval with synthetic at the dealership

With all due respect to your friend, I don't believe this is correct. If you change your oil with oil that has the same additive package, you'll still get the same protection (it'll just come from cleaner oil).

Everything else he said - True.

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My car sees only street use, about 70% freeway and 30% street use in flowing (not stop-and-go) traffic, and in 70 - 95 degree ambient temperature. Given those operating conditions, 3K oil changes would be downright silly. I've been changing mine at 5K intervals with premium full synthetic oil and oil filters, and I'm sure I could easily and safely take it to 7.5K mile intervals (but there's no reason to, other than saving a little money, and it really is "little money" in the big scheme of things).

Nissan here make you service your car every 5000 km so 3100 miles! Annoys me, but then I guess we are always running the engine at very high temps, especially right now when the air temperature is 43 Celsius.

Alot of things are done not because they are the best thing for you individually, Oil grades in the US have constantly been dropping (10W-40 to 0W-20 or lower) why? Because its a simple way to improve emissions across the board along with other improvements, it's not for longevity. Using less oil for the entire EU will reduce consumption, slow down fuel price increases, and pollution.
In the end Oil and engines have improved to some extent and the 3k or 3 months doesn't apply, not sure it ever did, but some cars, like BMW have had issues with extreme oil change intervals.

pretty soon engines will only use water.



ok, maybe not.

Yep (43C = 109F), that's hot.

No worries lads. I just read on the internet that engines will now use only water for fuel and lubrication. :tup: