Does Low-Grade Gas Save You Money?
Scrimping at the pump may not pay off in the long run.
I think you got it wrong about the sensors "ushering in more fuel" upon detection of low-octane. First off, cars do not have sensors that directly measure the octane in the fuel system. Secondly, low octane fuel has no less energy than high octane fuel, just less ability to resist pre-detonation (commonly known as "ping" or "knock").
Pre-detonation occurs when the fuel-air mixture in the cylinder ignites prematurely (while the piston is still too far from top-dead-center) and usually occurs under a heavy load such as climbing a hill or accelerating briskly. Ushering in more fuel would be akin to simply pressing further on the accelerator, which is unnecessary and useless given that the two fuels (high and low octane) have the same energy content. The problem isn't insufficient fuel, it's a combination of low octane and high compression.
The sensors that do get triggered due to low octane fuel are pre-detonation sensors. These sensors retard engine timing to reduce the pinging, but in doing so they reduce engine performance. With less engine performance, the car's mileage suffers and that's why high-performance cars tend to be more economical with high-octane gas. And yes, I can see where constant actuation of these sensors and constant timing retardation could lead to problems in the long run.
It's true. I tried this once in my Firebird, for which premium (91, minimum) is recommended.
The car ran fine on 89, but lost about 3mpg as compared to the 93 octane I normally run in it. Considering that 89 was only .15/gal cheaper than 93, it made no economic sense not to run 93.
This was 2 years ago, and I haven't used anything other than 93 since.
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