1) not sure, my engine has been ok (knock on wood - not metal
2) i use the Jiffy Lube Pennzoil 5W-30
3) not sure about cylinder walls, but I've heard that synthetic does not "treat" any non-metallic parts very well, it doesn't have any conditioners to keep things "soft" so parts may become brittle - although I've never personally seen this....
4) simple answer yes, others will chime in here
5) i've stretched it to 5.5K, the oil looked fine so I wasn't worried
major benefits? reduced operating temperatures and much quieter valvetrain and overall quieter engine - more responsive or horsepower? hmm, couldn't really tell - but the engine does run "smoother"...
good luck!
T
