All Lubed up!

[Blackrider]

[GT-R]

My 2 cents.
#1. Think of your engine as a machine shop. While the engine is running it creates heat and builds up carbon. This carbon although microscopic mixes with the oil, and is what tends to wear out the moving parts. This is why above all, I prefer to change the oil out regularly. Regularly to me is around 2500 miles for conventional oil and 3000 miles for synthetic. I say for me because, my cars tend to be driven to the edge of the envelope most of the time, which creates more heat and carbon. If you run an engine which is supercharged or turboed, synthetic is a must. Synthetics handle heat much better, thus gives you a level of insurance. I'm not one of those that believes that by running synthetic I should be able to change the oil every 6 to 10 thousand miles. The carbon build up within those miles are excessive in my opinion. As you all know, right after an oil change the oil appears clear, but as the miles are accumulated it begins to get darker. The darkness is a by product of the carbon buildup. The darker the oil, the more carbon it has within it.

Now, modern engines are built to a different standard, they run cleaner which in turn produces less carbon. If the vehicle is used for normal use, with no prolonged hard driving, and if you use synthetics, then it would be ok to get more mileage from an oil change, so long as the engine has not been modified. Some auto manufactures even offer this advice in their manuals, but only when synthetics are used. Oil is the life of any engine, so keeping the oil fairly clean is # 1.

#2. Don't rely on the filter, cause the filter does not filter all of the oil. All
engines use a bypass system. This allows for most of the oil to bypass the filter at a set psi. The reason for this, is to keep the filter from exploding. If all the oil were to be filtered, it would not take long before the filter would become clogged up. The pressure from a clogged filter would cause the filter to explode. This is why the bypass is there.