lol warranties. have you read BMWs suggested oil change interval? once a year. because they claim they use "special BMW oil" i won't even comment on this stupidity. and then this is what BMW owners listen to.
I know it is so old skool to get over the "oil changes are cheap insurance" and that oil has to be changed every 3000 miles mindset.
But keep in mind that those are the same oil change intervals that were being used in the 1960's and 1970's with engines that were much "looser" and had more
blow-by that contaminated the oil with combustion gases, that ran cooler and thereby didn't evaporate all the water out, and actually "used" oil between oil changes.
And those were the days of oils with very rudimentary detergent and other additive packages.
Nowadays, engines are much tighter so far less blow-by contaminating the oil, engines run hotter so less water in the oil, and engines run much cleaner than they used to.
Also, modern oils have incredible detergent and additive packages that neutralize the bad stuff and keep the "dirt" in suspension in the oil. It is the additive package that wears out. The "oil" itself (synthetic or dinosaur juice)
never "wears out". It just gets dirty.
So BMW engines are very tight and they use Castrol Syntec which has an incredible additive package. I know a senior engineer with BMW who was involved directly in the testing of the extended oil change intervals. From the testing stations in the arctic circle to the desert. He said that the oil provided protection for at least 100,000km. But they knew that the public would never beehive it and so they went with a one year interval.
Look, BMW would have to pay for worn out engines if they wore out. Tell me of ONE case where you know of a modern engine that wore out prematurely because of oil failure?
Now, OTOH, Toyota had real problems with SLUDGE build-up. That caused engine failures. That had a lot to do with wayyy too long intervals on cheap dinosaur juice.
Semi-Synthetic oil is fine for normal driving in any modern car engine for at least 15k or one year.
then you see 7 series on autotrader going for 15k
Has nothing to do with worn out engines. The 7 series is only "cool" to drive when you have the current series of the model. Otherwise it is ghetto. Plus, they are rotten cars to maintain outside of the engine block. So many electrical, transmission and electronic problems. Very sophisticated car with no reason for the factory to support low cost parts.
OP if you don't want headaches.. just buy a corolla or civic, change the oil every 5k. and it will probably run longer than you want it to.
Sounds like a granny car! Or a grandpa car!