im just very courious as to what exactly makes oil turn black afer being in your engine for a while

 

Stick your hand in 200+ degree conditions and see what color it turns

 

good enuff explanation for me

 

Its not just the heat, it is all the other things that it picks up along the way, small amounts of piston blowby, microscopic dirt, impurities in the oil itself....

~M~

 

Unless you have some really unusual conditions occurring in your engine, the dirt in the oil is mostly just that - dirt. Atmospheric dust that gets past the air filter is the main contaninant of most engine lubricants. A good quality oil filter will entrap most of these particles, or at least those that are large enough to cause damage. Some of the dark color can also be from combustion byproducts (mostly carbon) leaking past the rings, even in a new engine.

All these contaminants are the primary reason to change you oil on a regular basis. Unless you have a dual, staged oil filter setup like larger trucks/implements and stationary engines, you need to get the oil and filter changed when the contaminants can no longer be filtered. Some people running synthetics subscribe to the theory that changing the filter every 3,000 miles and oil every 6,000 miles is acceptable. It may be O.K., or even at higher mileage than that depending on the type of mileage and use the engine gets. That isn't even an option with mineral oil, however.

 

Vader, I'm surprised at you, perpetuating old wives' tales.

The #1 source of blackness is broken down petroleum base lubricant and additives (particularly VI improvers).

#2 is injested airborne dirt. Why wait for the oil filter to get rid of it? An oiled open-cell foam filter will pull out more and smaller dirt particles than any other type out there. And, don't say "K&N" to me, they aren't any better at this function than the standard pleated paper element.

#3 is combustion by-products.

3000 to 6000 mile oil changes with synthetic? Perhaps with a me-too brand, but I've been doing 25,000 mile/1 year changes, with filter change at half that interval, with AMSOIL engine oil, air and oil filters since 1983. Eliminate the #1 and #2 sources of contamination, #3 will be reduced as well, and you can do extend that drain interval and have a longer lasting engine to boot.

 

Four oil changes every 100 thousand miles. Man you have a pair WAY bigger than me.

 

Got nothing to do with it. It's all in what's between the ears.

Besides, I rarely drive 25k in one year, so the mileage is more like 15k or so - although my dad did, with an '89 Bonneville that had 170k on it when it was totaled in '98. Thing still ran like a top the day of its demise, used a quart in about 10k miles right to the end. It had had 10 oil changes total, including the change-over at 5k.

 

Hopefully not too much wax.... j/k

So at 15k, that comes out to 6 2/3 oil changes per 100k miles.

Conventional oil (and some synthetics) 20-33 times per 100k miles.

I understand that Amsoil is a better product. I also understand that there is A LOT of metal to metal contact in an engine, so some of that metal will wear off and get washed into the oil as suspended precipitate. No filter is going to catch ALL of those abrasive metal particles.

These metal particles occur at a fairly constant rate once the engine is broke-in. Oil changes done less frequently will allow for a higher concentration of these abrasive particles to accumulate and be circulated throughout the engine. It is the removal of the engine oil that removes the suspended abrasive particles.


BTW, the use of had had in your last sentence is grammatically correct, but to me it has had never sounded correct....