[tmaxmetro]

I'm no chemist - but I do know that the oil I drain out of the car is usually much thinner than the oil I put into the car - even after I let it cool down and reach the same temperature. The drained oil is also considerably darker than the oil I put in.

So what has happened between the time you put the oil into the car and when you drain it out of the car? I'll assume :
- contaminants in the oil like sludge, carbon, dirt, gasoline, steel, etc.
- breakdown of the oil caused by repetitive heating/cooling and being pumped around

Is a $3 quart of oil 3 times better than a $1 quart of oil? I doubt it. I'd probably lean towards the advantages of buying cheaper oil and changing it more frequently. You'd be saving money because the oil is cheaper - the engine would most likely remain cleaner, and the oil in the vehicle would be fresher.

Although my practise is usually to make sure the oil level is good, change the oil at a decent interval and not give brand name too much thought...

cheers,