Getting ready to change the oil, no idea what was used last, or when. Have put about 600 miles on the rig since purchase. It's getting 27 mpg. Have used synthetic in other vehicles, but...this is an older engine...no idea, really, what is best. Any suggestions? Oh yeah, 240 DL 1988 model, 185K miles.

BTW, found answer to the "bad air quality" problem I posted before. Husband spent about 30 minutes placing a shim on the exhaust pipe behind the (?) catalytic converter (?) amidship about where the passenger footwell would be...he put a shim and tightened the clamp. Solved the air quality, vibration, hollow ringing metal sound problems all in one stroke...