Originally Posted by mcmmotorsports

Okay, everyone please be seated...Class is about to begin.

Now, first off, Quaker State and Pennzoil are the same oil, made by the same manufacturer. Valvoline is made by Ashland. They also produce the oil for Napa.
Havoline also makes Shell oil and Advance Auto Parts branded oil.
Amsoil is all by itself, so is Mobil 1.Mobil conventional oil is the same as Exxon superflow since Exxon/Mobil is one company now.
Castrol also is in its own class, no one makes Castrol oil but Castrol.
Rumor has been that Havoline makes Motorcraft, but I have not been able to confirm this. I don't believe they do. 9 times out of 10, you will have a hard time trying to find who makes what oil for your Generic places (Wal-Mart, Target, etc...)

Oil Change Intervals....

Oil should be changed every 3 months or 3,000 miles or whichever comes first.
It should be changed more often if the following conditions are met:
1: You have frequent stop and go driving, ie..live in a heavy traffic area.
2: High Performance applications...higher engine oil temps will greatly reduce an oil's lifespan and break it down quicker.
or 3: Drive in dusty conditions, ie...construction.

Benefits of a Synthetic:

Lower oil temps
Longer Change Intervals
Better protection at startup
Better Fuel Mileage
Higher horsepower.

I didn't copy and paste any of the above info, I have witnessed with my own 3 eyes the lower oil temps, better fuel mileage and higher horsepower.
I had a sponsor (Torco Racing Oils) who provided oil for one of my dyno sessions back in 1995. Temps were 20 degrees cooler and we picked up 7 hp just by switching to synthetic.

Now, with that said, here are some more FACTS:

Quaker State and Pennzoil have the HIGHEST content of wax in their oils. Said to help protect engine components, but sometimes helps to burn alot quicker too. DO NOT USE those oils if you have a consumption problem. Use Castrol GTX which has the LOWEST content of wax.

Switching from a Conventional Oil to a Syn. You can do this, even in high mileage cars, but keep in mind you MIGHT develop a consumption problem due to the increased lubricity of a Synthetic. Just switch back if you have this problem.

The biggest rumor put to rest....

Fords required 5w-20. Can I use a 5w-30 instead? ABSOLFRIGGINLUTELY!
Ford switched everything to 5w-20 to help meet the Cafe standards set forth by the fabulous US Govt. They found that the reduced viscosity help increase gas mileage like ..0006%. Multiply that by how many cars Ford sells and voila, they come up smelling like roses with the feds. As a car owner, you can use whatever you like. Personally, 5w-30 is what I have in my '04 GT. I was using Mobil 1 since 1,200 miles, but switched to Castrol once I put my S/C on. Two reasons for the switch...no longer go for 5,000 intervals and I'd go broke changing Mobil 1 every 3,000 and two, the tuner recommends a dino oil instead of a syn in blown applications due to the chance of blowby. Now that I don't drive my car daily, I am probably going back to Mobil 1. If I develop a blowby problem, I will go back to Castrol.

BTW, I am an ASE Certified Parts Specialist, so I aint making this crap up.