RE: Oil analysis
I bought a brand-new '93 Ranger SuperCab 4.0L V-6. I changed the oil and filter at 3000, 6000, and 10,000 miles with conventional oil. On the 15,000 mile change, I switched to synthetic.
I have changed the oil every 15,000 miles whether it needed it or not. I have changed the filter every 7,500 miles and topped it off between oil changes.
The truck now has 160,000 trouble-free miles. I have never even removed the valve covers! I have looked down into the valve covers with a flashlight and there isn't a trace of sludge. The dipstick is still clean and sludge-free.
Say what you want, but I am convinced that I have saved a lot of time and money by ignoring the naysayers. I will admit that I'm wrong if the engine ever wears out. But at this point, I have saved roughly 41 oil changes...