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I have heard that revolutions per second effect has mileage negatively, but I haven’t heard by how much.

Is the relationship linear-ish (like with a little wiggle room for error)

Or is the relationship exponential? Like 6k RPMs use a lot more than 5.5k RPMs

If I had to guess, I would choose a mix of the two. Cause I believe a four stroke engine’s (1. in, 2. compress, 3. boom, 4. out) cylinder takes in fuel once per 4 strokes. But I could be wrong....I probably am. I also think that the “intake stroke(?)” can be adjusted by a computer if it so pleases. Is my research correct, flawed?

Any info or links would be nice and appreciated.

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  • Agh. I forgot... when I said linear i forgot to add “linear like 3k RPMs use twice fuel as 1.5k RPMs”
    – Zeno
    Commented Feb 12, 2018 at 1:40
  • Welcome to Motor Vehicle Maintenance & Repair! In the general sense, given any single engine in a specific car, the higher the RPM the more fuel which is consumed. If there was no load on the engine, then as you rev the engine, gas consumption would pretty much be linear (to a point). When an engine is under load, like with wind resistance while driving, as the engine speeds up, fuel consumption will be more exponential.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Feb 12, 2018 at 1:57
  • Huh. Didn't know about the load thing. Thx.
    – Zeno
    Commented Feb 12, 2018 at 2:25
  • check out "Brake Specific Fuel Consumption". Oh, also the load due to air resistance is not linear...
    – Solar Mike
    Commented Feb 12, 2018 at 4:47

2 Answers 2

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Fuel consumption depends on number of strokes per minute multiplied with fuel intake per stroke. The number of strokes per minute is linear to the rounds per minute.

The fuel intake per stroke however, is not. If you pushed the accelerator pedal, the air intake increases and the fuel intake per stroke is adjusted accordingly. That's the function of a carburettor and also the function of a fuel injection.

If you had to step on the accelerator e.g. to drive a slope upwards at steady speed, RPM stays the same but fuel per stroke is much higher than on a flat road.

If you don't drive through vacuum (unlikely), there's also the wind pressure, which demands power depending on the speed squared. So if your car needed 3kW alone for working against the wind at 50km/h, it needed 12kW at 100km/h, 27kW at 150km/h and 48kW at 200km/h.

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The relationship is linear (with "wiggle" room). I have read that a two-cycle engine will burn approximately twice the gas at full throttle as opposed to cruising (something like 5,500 RPM vs about 2,200 RPM).

I have personally experimented with my old car (which is in very good mechanical condition). At highway speed, the car burns 25% more gas when I downshift and raise the RPM 50%.

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