OK...so I've compiled the answers as accurately as I could. All I have to say is WOW. That's a lot of dinosaurs on the road...both in terms of the oil used and the longevity of your vehicles
I wonder if the underrepresentation of synthetics on this list is due to the % of people using dino vs. synthetics, the length of time synthetics have been on the market, or simply because of random chance?
355,803 Mobil 1 High Mileage
346,000 Mobile 1 and other synthetics
390,000 Mobile 1
284,000 generic dinos
391,000 Valvoline White Bottle
297,000 Castrol GTX and Quaker State Green Bottle
330,000 Pennzoil Yellow Bottle
350,000 Pennzoil Yellow Bottle
296,000 Whatever was on sale
380,000 Whatever synthetic was on sale
300,000 Mobil 1
600,000 Quaker state dino
471,000 anything
300,000 anything
671,000 anything
370,000 anything...sometimes synthetic
290,000 cheapest thing available
300,000 anything
407,000 Motorcraft
422,000 Castrol GTX and PYB
350,000 Valvoline White Bottle
394,000 Valvoline/Halvoline/Quaker State
300,000 Quaker State
300,000 Valvoline/Pennzoil
300,000 Pennzoil Yellow Bottle
410,000 Whatever synthetic is on sale
314,000 Whatever was affordable
331,000 Valvoline White Bottle
334,000 Pennzoil Yellow Bottle
294,398 Pennzoil Yellow Bottle
300,000 Whatever
368,000 Whatever the dealer used and then Mobil 1 @ 277k
270,000 Castrol GTX and Chevron Supreme
300,000 Castrol Syntec
300,000 Conventional