Originally Posted By: raytseng
Originally Posted By: Wolf359
Originally Posted By: HTSS_TR
Most stations in Orange County, So Cal have 10 cents spread, some have 12-15 cents spread and some only 8 cents different.
With extra 16 cents(above $3.8x/gal regular) for premium I fill up the Volvo with it. Because it costs only 5% more and usually Premium has more detergent, and it seems to get 1-2% better gas mileage.
That's the marketing talking. My gas mileage varies from tank to tank by more than 1-2% and it's the same grade.
The btu content of regular and super are the same.
Mid grade might be the one marked up the most. Midgrade comes from mixing super and regular. If you have 93 super and 89 midgrade, sometimes it's just cheaper mixing it on your own. With 91 super, then it's just a 50/50 mix otherwise 93 would be a 66% regular 33% super mix.
well, that's assuming your car doesn't adjust timing and take advantage of the octane rating. If your car can adjust timing and increase compression, then despite having same btus in liquid form, it can produce more usable power and work out of that fuel. Majority of the BTUs is "lost" anyway, the engine isn't creating extra BTUs out of thin air, it's just able to turn more of them into work.
By your logic, because the btus are the same in the fuel, all engines should produce the same power and useful work out of the same amount of fuel btus. Obviously that isn't true.
Normally you can't increase compression, that's from the design of the engine. And you normally don't increase timing, it's normally already optimal unless timing has been retarded due to knocking. So all else being equal, a proper running engine doesn't benefit at all from super. Again, it's all about the marketing.
Your logic is also faulty, I'm saying that the SAME engine doesn't produce more power just from using a higher octane because the energy content of the fuel is the same. It's known as comparing apples to oranges. Of course different engines will develop different amounts of power. Logically, you should use the scientific method. That is repeatable, reproducible results. People who report slight better gas mileage using super aren't using the scientific method, they're reporting anecdotes which isn't scientific. More like the placebo effect is in play than any logic. The scientific literature all says that higher octane won't get you better gas mileage in the SAME engine if it's designed for regular gas. It's the marketing that will make you think otherwise.