mack-attack

Heres a off the wall question. the subie i have is a 1998 outback with 183 thousand. i bought it from a dude that had the engine rebuilt. newgaskets,head,timming, piston rings, bearings waterand oil pump and new clutch. when i got it home i drained out the regualr dino mobile1 5-30 and put in dino 10-w30 rottela. should i have not don this? it seems to have helped the slap. but i also noticed that it has started to leak fresh oil. i dont really know were its comming from. maybe the valve cover? would this happen when the engine was rebuilt less then 50 miles ago? could it be from the rottela? thanks p.s. its not comming from the drain plug or filter...

update: after my new oil changed listed above, i started my subie after it had cooled to the point where i new the slap would start again, and it seems like the slaping noise has lessened! while it still make noise it isnt as loud and it seems to fad somewhat faster also. It may be the heavyer weight oil and the lucas working together. anyway it seems like it has helped! it also seems to idle smoother? my 2 cents.. So whats your guys opinion. which one would be better? rottela 10-w30 or the standard mobil1 5-w30? my subie has 180,000 and has a partially rebuilt engine(new head,timming water and oil pump). at the moment the new rotella seems better but Im not harming my engine am I? I got the oil at walmart for like 12bucks and used half a bottle of lucas synthetic oil stabilzer. any thoughts or comments would be welcome.

So I changed my oil and tried the dino rotella 10-w30 and some lucas synthetic engine oil. I had some dino mobile1 5-w20 in it previously. well see how this handles the piston slap. I just hope this "diesel" oil is safe...

so i read through this old thread quick. what is the best oil to try and quiet down the "slap"? wouldnt 10w30 be better then 5w40?