Cleaning up today and I found some old oil change records. Car was a mid 80's 4-cylinder Holden Camira, the GM J-body also sold as the Opel Ascona, Vauxhall & Chevy Cavalier etc. I picked up the car second hand in the mid 90's with about 150,000 km (93,000 miles) on the clock. I was mostly motorcycles up to then but a smoking hot girlfriend who was OK with the occasional sunny weekend ride, but much preferred to go grocery shopping on a rainy night in a car. Go figure. Oil spec was API SF 20W-50 every 10,000 km (6,200 miles) or 6 months. Most oil changes were mineral 20W-50 (API SH) at about 8000 km (5000 miles) with Mobil Super XHP, Valvoline XLD and Castrol GTX-II. By far most were the GTX. However back in the 90's I was already using full synthetic in my motorcycle, and so they also made it into this car (when I could afford it). I did a few changes on Castrol R Synthetic (now called Edge) 10W60, and a few changes on M1 5W-50. I ran the synthetics out to about 12,000 km (7,500 miles). I have one shockingly long oil change of 22,500 km (14,000 miles) on GTX 20W-50. But I think this is more an error of my note taking as I believe I also did a run of Castrol XL 20W50 in this car, but it's not in my notes. If we assume the above is a note error, then my longest run was 17,700 km (11,000 miles) on Castrol R 10W-60 full synthetic (PAO based back then, I range and asked them). Car went to the wrecker / breakers with a good engine but the body falling apart. My timing was perfect, it dumped its radiator in the car park of the wreckers, and I drove it in the last 50 meters dry.