It's not that they can't, it's that it's not in their wheelhouse. The R&D required isn't in their interest, nor is the quantity. The big brands are blending multi-thousand gallon batches so smaller batches for a niche are outside of their scope. The R&D for their oils are mostly done by the additive companies like Infineum and Lubrizol, who will put together an additive package that meets API SP (or whatever standard). In blending the oils, Valvoline, Castrol, etc... will buy the add pack, blend it in base oils per the provided recipe with the add pack, slap a starburst on it, and send it out the door. They likely take a sample from each batch for QC purposes, ensuring the blend went according to plan, but that's about the extent of their lab work. It's not like the small brands like HPL, Amsoil, Red Line, etc... who have full purpose dedicated labs in house, live fire engine testing, freedom away from the API umbrella, and are easily setup to blend one-off batches as small as a 5 gallon pail with remarkable accuracy. While the big brands could certainly do that, their focus is elsewhere. The small blenders are way ahead of them in terms of R&D in the racing world.
They do produce "racing" oils, with Mobil 1 Racing probably being the one with the most R&D behind it of the big brands. (judging by the add pack and properties) Oils like VR1 are essentially white bottle Valvoline with 80% more ZDDP so not really anything special but serves the purpose.
To blend an oil for a NASCAR cup engine, there's testing involved that you don't see in typical API stuff. Things like SRV for seizure and friction coefficient, CFR octane testing for the inevitable oil transport into the chambers, adjusting formulas to achieve more power through the burning of said oil, etc... Sometimes it involves blowing up a $75k engine (or multiple $75k engines) to keep pushing that envelope.
Usually no. They'll go 4-5 races on an engine. Even then, they only swap out the engine to keep a fresh bullet in the hole. They could realistically go an entire season on one engine if they really wanted to, (some low budget teams may go 10+ races) but you start to see a slight power loss after 2500 miles of sustained WOT and 7500+ rpm, mostly attributed to the thin rings just wear out from the heat and not sealing as well. A lot of times, the cylinder crosshatch after 4 races will still be as beautiful as when it went together. The valve seats also take a beating from the spring pressure and cam lobe intensity, valve springs wear out, etc... It's rare that an engine is pulled due to a mechanical failure, much less an oil related mechanical failure.
