hey guys, i recently bought a 04 ranger, 2wd 62,000miles with what i thought was a 4.0 i went to change the oil today and the filter they gave me was too big... brought it back and come to find out i have a 3.0 (8th digit in the vin is U the auto parts store told me its a 3.0)

well heres my issue, when i test drove the truck it ran fine, the owner told me it had a small oil leak, when we came back the truck was down 2 quarts of oil. the valve cover cap says 5w-20

when i went to pick the truck up i bought 2 quarts of 5w-30 by mistake, threw it in to get me home, well ive put 300 miles on and the sucker wont drip oil!! i decided since i didnt know when the last time the oil was changed to change it this morning, and i put motorcraft semi-synthetic 5w-20 in it

well i got the leak back!!

my question is it looks like its the real main seal, since i had 5w-30 in it and it didnt leak ( btw it was motorcraft semi synthetic 5w-30 as well) do u think its safe to go back to 5w-30 so the leak will stop?

thanks for ur advice!

danny