They have gone back and forth on the hole synthetic gaining horse power thing. I have read a few articles that do support small gains with the higher grade syn oils. Most are around 5-8 horse power depending on the engine. There is no question that synthetic oils offer better lubrication then conventional oils. As far as changing your oil a lot depends on how hard you run the car and what kind of area you live in but you should be able to get around 5,000 miles with no problem unless you are hitting the track hard constantly. As said above synthetic oils are great if you are going to be storing you car for long periods as well. I have always liked royal purple personal i run 20-50 in my TA and have never had a problem. On the other hand i have run mobil1 syn 5-30 in my 2.8 that now has over 230,000 miles and has never had the valve covers off.[>:]

 

the way i heard of oil raising hp is if you use royal purple in the motor, trany, rear end, and some kind of radiator stuff that keeps the motor cooler but idk about that i use moldile 1 in my motor royal purple in my trany and rear end...

lol royal purple and rear end in the same sentince...you can make one perverted joke with that one

 

Anything that frees up movement and creates less resistance in the engine also frees up horsepower. Just like with roller rockers, roller lifters, etc.