Oil doesn;t matter that much as long as you keep it clean. That means regular changes.
A heavy oil is good for older engines as the tolerances have been worn open a bit and this will help fill in the gaps a little better.
All brands that are certified, which I don't know where you would buy anythign retail thats not... will protect your engine.
Synthetic is better, engine tear downs have proven this.
try to match to weather conditions. I tend to use 10W30 Penzoil in my 5.0 in the summers and 5W30 in the winters.
In my new car, I use the Motorcraft synthetic that the dealer puts in (hey they only charge me $11 for an oil change since I bought the car there) Its the only car I have ever owned that I don't chage my own oil in.
Perfromance wise, there hasn't been much proven as major power losses or increases. I saw a write up somewhere where Redline did a test on an Impala SS (LT1 version from the 90's) replaced all the organic fluids with Red Line's Synthetic. That was oil,
Tranny fluid, Rear End Fluid, Power Steering Fluid, and I cant remember if there was anythign else. They showed a gain of 10hp. Now think about the extra money that will cost you over 2 years with a Daily Driver. Is that 10hp worth that? I could see it in a Race car though.
For an Engine burnign oil, or lifters ticking, I have found that the Lucas oil that you can mix with anything help a lot. Quiets everything down and reduces oil consumption.
