Ok so when you go to the gas station there are three "grades" of gas (there's also diesel but that's not relevant here):
- Regular - this is what pretty much most people get.
- Plus - Why????
- Premium - for luxury/sports cars
So can someone explain what the hell the "plus" is for?
Some cars that operate at a higher compression in the engine needs a higher octane gas; turbo and supercharged cars, mostly
Yep, and now that most cheap economy cars are turbocharged now they require higher octane fuel to meet their published MPG rating. So it isn't just about cheaper gas for cheaper cars. The manufacturers account for this, and build them so they run on lower octane fuel anyway knowing how careless the average carowner is. But it isn't optimal, and you may even be losing more money this way through loss of efficiency. But using "premium" on a car rated for 87 octane is a complete waste of money as nothing is gained by it. Back in the pre-internet days, people would spread some weird urban myths about gas, like thinking premium fuel would clean your engine or some other such nonsense.
OP is asking about mid grade and I think most new cars don’t specify it, only regular or premium. I think some imports from the early 2000s may have required 89 but I have never seen it irl
Even if they don't specify it, they often want it anyways. Most NA BMWs call for premium but will run midgrade, almost every Volvo calls for midgrade, Mazdas get a noticable improvement in performance from midgrade but only call for regular, etc.