Originally Posted by lddavis
You're talking past each other. No one said you can't use petroleum oil. The key is the phrase "proper change intervals", and the earlier mention of "price versus cost".
A quick check on Autozone.com gives me $4.79/qt for Mobil petro oil, and $8.99/qt for full synthetic. Assume five quarts of oil. Change the petro oil every 3000 miles. Change the synthetic every 10,000. After 30,000 miles, you've spent $239 on petro oil, or $135 on synthetic. In addition, you also pay three times the labor for changing the petro oil more often -- and even if you do it yourself, your own time is worth something.
Sure, you can keep the engine running, but the petro oil costs you more. That's neglecting other disadvantages like disposing of three times the waste and having the car down three times as often.
And as for frequent oil changes damaging the engine -- well, if you take it to a quickie lube place, every oil change is another chance for them to break something, so you want as few of those as possible :)
One of the most intelligent, well put posts here. Thank you.
As to why excessive oil changes can cause engine damage; every single time the oil is changed, the engine oiling system loses its prime and when the engine is started there is zero oil pressure and metal-to-metal contact going on inside the engine that it never see's at any other time in its life. That kind of wear can rob life from an engine, reducing it's operating efficiency, (reduced fuel economy and power), and longevity. It wont run, "like new", for as long as it could have. Excessive oil changes are not doing any engine a favor. Of course, the greedy big oil industry likes to siphon off consumers hard earned money if they can, but consumer groups called them on this and even the greedy big oil companies are now no longer recommending needless and wasteful 3,000 mile drain pain intervals.