try a thicker oil... worn engines have larger gaps between parts, so to compensate for that, a thicker oil would be the benefit. this will save your engine down the line. i suggest 15w30 or 20w30. you can also run 10w40 but throw in a bottle of Lucas Oil treatment.. thos stuff is sticky and very thick, so it will stau in between larger gaps for a longer period of time, quieting or even silencing any type of engine-related startup noise. i've used both methods in the past and they work great. the thicker oil method is the cheapest, being that Lucas oil treatment is aroun $7/quart (you need one for everey 4 quarts of oil)

if you do go the lucas route, i suggest pre-heating it to allow it to flow easier cause it takes 2 years for it to spill out. a good thing to do when your at the very end, throw in a bottle of 10w40 inside the lucas bottle, mix it up a bit then throw it back into the crankcase.. that takes all the residue out and makes your money's worth.