If you have 100 bucks get 3 oil changes anayized for yourself, any other statements are mere conjecture
Exactly. The manufacturer recommendations are advisable for most people. I do wish more manufacturers also published a mileage recommendation as a supplement to the oil life sensor, but I guess that would be too confusing for people. Most manufacturers recommend 6 months on conventional, 1 year on synthetic if mileage is below the change interval.
Colour and smell don't give you much indication of what's going on in modern oils, as dark colour by itself can be caused by the additives, and also means the oil is suspending dirt and other combustion contaminants rather than leaving them in the engine to wear or corrode internal components. It also gives no indication of age or moisture, as really black and thick oil might be a red flag of high miles and age, but relatively clean looking oil could be old, have higher moisture, with just as much need to change.
My car had anual oil changes at well under 10,000 KM according to the records, so I did my first oil change near the date in August with Mobil 1 5W30 and a Mobil 1 oil filter. I'll be doing it again this August, and have about 6,000 KMs on the oil right now. It's not winter stored and the longest it sat this past year was about 3 weeks when I was out of town.
On my G35 the manufacturer recommendation is 6250 KM or 6 months with conventional, 12,500 KMs or 1 year with synthetic, but I haven't driven much over 10000 KMs in the almost 8 years I've had the car, so I change it every year. It's had Mobil 1 5W30 in it since 60,000 KMs, now over 214,000 KMs. I used to use a Nissan oil filter, but started using Mobil 1 filters when the price went up and I found out they use cardboard end caps. I've done every oil change myself since I got the car at about 156,000 KMs.
