If all other factors are held constant, does fuel economy (number of miles per gallon of gas) increase or decrease with an increase in engine RPM? For example, is fuel economy lower at 3,000 RPM as opposed to 2,000 RPM or 1,000 RPM?
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Anonymous
ANSWERS: 2
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To get the best fuel economy from your car you need to keep your revs low, hence why higher gears are better than lower ones for the same speed.
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If ALL other factors are constant, then yes. In reality.... usually but not always. Fuel consumption is directly proportional to air flow. If the throttle position is held constant then the amount of restriction in the intake tract is also constant. However, there is a certain amount of inefficiency in the cylinder due to swirling. At certain RPMs, the airflow and swirling is just right and allows for optimal burning, thus turning the gas into torque more efficiently. Since power is the product of torque and RPM, and [insert two paragraphs of babble and jargon] it is entirely possible that one could get better fuel economy at the same vehicle speed at a HIGHER RPM, depending on the powerband of the engine and the gearing. To sum up, that is MOSTLY true... but not 100% of the time. I have had enough experience contrary to such accepted wisdom that I feel I must refute them. In this case, assuming all other factors CAN be held constant in the first place is absurd.
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