It’s not marketing hype and i wouldn’t trust any tuner that says any 5W-40 is fine, every tuner i know, mainly Audi and BMW, wouldn’t dream of just putting any old oil in, decent oil only. It is not just service life that is greatly reduced on cheaper oils (due to them not being a proper synthetic) but they do not have the proper sealant qualities, an oil has many other uses other than just lubrication, reducing friction (friction modifiers, forming a low shear film near metal-to-metal) and cooling (oil is responsible for dissipating almost as much heat as the coolant). Cheap oils are less effective at doing this and also less effective at keeping the engine clean (preventing formation of deposits, piston rings, oil ways etc)
Big oil producers work hand in hand with vehicle engine designers, right from the outset. This is to specify the oils performance is matched as closely as possible to the operating needs of the engine and is why manufactories recommend particular oil for there engines. Oil is not specified once all the engineering work and development is completed; do you think they want to spend millions on lubricant testing?
In bmw’s for example, they use on board computers to calculate the variable service interval. It monitors a range of factors, including number of engine starts, number of combustion events and oil temps etc. They are then worked into a calculation using an algorithm to determine the oil change interval. What is doesn’t do is check the quality of the oil. It is well known that severe engine damage occurs if none specified oil is used in BMW’s if poor quality oil is used and the user goes by the on board computer.
I know we only have s**tty Renaults, but i personally use the same principles on any of my cars, use what the manufacture recommends or an oil that exceeds there specification.
