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I own a city car Chevrolet Spark 2016. When going up a steep hill say in 4th gear, having the throttle down at 60% or WOT is practically the same. There's a minimal increase in RPM and power. Will the vehicle consume the same amount of gas if at 60% rather than WOT? Is going WOT in this case harmful for the engine? Is it better to shift to 3rd and slowly gain speed or to 2nd and go faster, quicker?

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    WOT: Wide Open Throttle. Pedal to the floor. – JPhi1618 Apr 20 '16 at 23:27
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    If this would be a regular throttle cable based car you'd be lugging the engine, not so sure now. If the car does not accelerate after putting the pedal down - downshift. – I have no idea what I'm doing Apr 21 '16 at 9:24
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I would bet the engine in your car is drive-by-wire, which means the computer is controlling the throttle, not you. In doing so, it is going to look at the load put on the engine and a bunch of other factors and give it only the throttle it can use as well as the gas ... at least in high gear. By going WOT in this instance, you'll not be causing your engine any damage beyond the normal wear/tare.

As far as mileage goes, you will get worse gas mileage by downshifting than you will by keeping it in the high gear. This is because the engine will be revving to a higher level. More RPMs = more gas used. The difference is, you'll most likely be able to obtain a higher speed with the vehicle because you'll have more available hp/torque to the ground. It's the age old trade off of get there faster or get better fuel mileage ... take your pick.

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    For the sake of generalization, and at the risk of asking a new question in the comments... How would this change if the car was a cable-driven carbureted engine? – JPhi1618 Apr 20 '16 at 21:22
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    I was assuming cable-driven fuel injected would be the alternative. For that, when you hit WOT in a cable operated FI vehicle, the fuel map goes to open loop mode and runs it rich to control detonation. In a carbureted car and in the DBC FI car, WOT will use a lot more fuel without much better results. I don't know if that really clears anything up though. Scenarios are definitely generalized. – Pᴀᴜʟsᴛᴇʀ2 Apr 20 '16 at 21:50

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