Sythetic or Not?

[RockaRollaTruck]

Should i use synthetic 5w-20 oil or regular 5w-20 , and what kind?

[Rango88]

Originally Posted by RockaRollaTruck

Should i use synthetic 5w-20 oil or regular 5w-20 , and what kind?

I use Castrol Syntec 10w30 with a lucas blend, it works great

[Clinton]

I use Valvoline full synthetic 5w30, Good stuff for me!

[matt224]

Synthetic all the way. Conventional can;t compare any more

[mickblock]

Valvoline full synthetic here also.

The big difference with synthetic is that it does not require additives to flow at it's viscosity rating. Conventional oil always has. Nothing wrong with using additives to modify viscosity charactoristics across the required temp ranges other than the fact that those additives are what break down.
This is just specualation on my part but I think the reason that 3,000 miles oil changes exist is either because
1) The reason stated above
2) Engines were not required to be nearly as clean burning as they are today. The crankcase accumulated alot more disolved solids and acidic combustion waste.
3) To sell more oil.