Yeah about 4 years ago I let her oil change slide once to a 11,000+ mile interval. We were in the middle of building the house and birthing #2 child etc. After that one time is when I noticed the sludge build up in the filler hole. Before that one time I had been "religious" about changing it around 6,000 miles with Castrol dino. Sounds like could be an accumulative thing especially if you go to 7k+ between changes in warmer climes.
I've been watching the oil level real close since the rear main drips. We've been on several long distance trips in it and I just keep my fingers crossed it doesn't let go at the wrong time. When I get my shop finished I'll take it out of service and drop the drivetrain to fix it. Maybe I'll go to Mobil1 too. Really need to trade it for that rumored BMW minivan LOL!
John R.
1992 525 IA, EAT chip, 16 x 7.5 Rondell 58's, BavAuto Springs, Bilstein Sports, Elipsoid Smileys & fogs, Z3 Pistol grip shifter, 4 VDO gauge package, Azure Blue w/nice patina - clearcoat shot