Yes those are not real world numbers, those are tested in a lab with "normal" driving habits. Im pretty sure most people on this forum are above normal in the driving habits as in off road allot, or go WOT allot and have performance mods done to there motors.
All those things throw off the 5,000 miles. The only real way to test to see if your, engine, your driving style, your environment is ok for 5,000 miles or more on a oil change is to send you oil in for testing by getting an oil analysis.
That will tell you how much life is left on you oil and other problems your engine may or may not have.
My brother uses
blackstone-labs
Also i drive my vehicles to way over 200K mark so every little thing i can do to make it run better, last longer and get better MPG ill do.
far as cost.
Say you spend $45 on you oil change. at 5,000 miles thats $0.009 cents a mile
Now at 3,000 miles its $0.015 cents a mile
so thats only $0.006 cents a mile more. Yes thats less the a penny
Ill spend that to make my engine last long and more.
Also i have seen the inside of a engine that was changed every 3,000 miles on the dot for over 150,000 miles and it looked new inside.
