I would have thought 3 mos 3,000. I kind of remember first change at 1,000. I looked at the owners manuals for 67 and 74 I was blown away. 67 said Change oil every 60 days even though less than 1,000 miles have been driven. If more than six thousand miles are driven in a 60 day period change oil every six thousand. The 74 manual states Change oil each 4 months or 6,000 miles. If more than 6,000 are driven in a 4 month period change oil each 6,000 miles as what Joe said. Then its said under dusty or trailer pulling change 2 months 3,000 miles. I change my oil by the look and smell method or by the season or by the show our cars or should I say my cars dont get many miles put on them. My driver 65 gets maybe three hundred a year. Pete would love to see your cars esp the L89s.Phil 8063 Happy Motoring