The WRX is turbocharged. The base model Mustang is tuned considerably downward of the Vette’s motor. That’s why the differences in octane requirements.
Most “normal” cars (the Vette and WRX are not normal) that require premium gas require it due to compression ratio. Mine has 11:1. Sure, it could auto-retard the timing and reduce the severity of the predetonation, but it couldn’t eliminate it entirely. I knew what I was getting into when I bought the car. It required premium fuel. I knew that meant I’d be paying 20 cents more per gallon, or a max of 2 bucks more per fill-up, as a result. If I had had a problem with this concept, I’d have bought a different car.
Which is what the OP should have done, rather than buying the car, and then trying to get a bunch of guys on the internet to justify his decision to ash-can the manufacturer’s instructions so he can save 2 bucks a week.
I know that sounds harsh, but at the end of the day, the manufacturer doesn’t care how much you spend on gas. They have no vested interest in getting you to spend an extra 8 bucks a month on fuel. There is no vast conspiracy between the auto makers and Shell to bilk you out of pocket change. So if the manufacturer tells you to do it, there’s a good reason for it, and trying to find excuses not to follow the recommendations becomes tiresome when it’s the 300th post about it.
I think you missed the point. The Taurus SHO is turbocharged as well as has a far high compression ratio than that of the WRX yet it runs happily on 87 octane, whilst the WRX requires premium. Take the Mustang GT and Camaro SS. The Mustang’s new 5.0L DOHC has an 11:1 compression ratio yet it can run on regular (though premium is recommended). The Camaro SS has 10.7:1 compression ratio and it’s premium only. To reiterate compression ratios don’t mean as much as they did 30 or even 10 years ago when it comes to fuel requirements.
I wholeheartedly agree that when you buy a car that requires premium fuel you should be prepared to spend the extra two bucks at the pump and use the correct fuel. I shake my head in disapointment when I see someone pull up to the gas pump in an M3 and then procede to fill it up with 87 octane.
Rather than how fast a fuel burns, I always understood octane to be a measure of a gasoline’s self-ignition “flash point” temperature.
Correct!
I do understand where you’re coming from, but when I say “compression ratio,” that’s really i-don’t-want-to-type-all-this for “combination of compression ratio and an ECU that is not designed to retard the timing enough to run damage-free on 87 octane with the compression ratio that the car’s engine has.”
You could make an engine’s compression ratio as high as you want (within reason), and as long as the timing is sufficiently retarded, you won’t get predetonation (assuming, of course, that the engine is clean and does not have an excess of carbon buildup). But you also won’t get anywhere close to the power output the engine is capable of. The makers of the luxury cars figure that if you’re buying a luxury car in the first place, you probably won’t whine about paying for premium fuel.
Cars with “premium fuel only” are generally aimed at people who are looking for a certain level of performance, and who are willing and able to pay the extra 2 bucks a fill for premium.