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For a flat road with a maximum speed limit of 60 kph, which would be better for a 2.4L 4CYL i-VTEC gasoline engine (K24A4 rated at 160HP @ 5500 rpm, 218Nm @ 4500 rpm):
3rd gear at 2500 rpm
4th gear at 1100 rpm
Will there be a difference in fuel consumption or would one be better for the engine, transmission, etc?
I assume we're talking about a car with a normal rpm range here? If so.. And the vehicle had a max rpm of about 6000rpm.. Then It would likely be more fuel efficient at 1100rpm. However.. At 1100rpm an ordinary engine is only a few rpms above tickover, so smoothness and driver/passenger comfort must come into account here, especially as even slight inclines in the roads surface would lower the rpm further taking the engine towards a stalling condition, this then would increase vibration etc further so more throttle would be required, unless you then changed down a gear anyway.
A vehicles fuel efficiency monitor will likely tell you at 60kph to change up a gear from 3rd to 4th for economy, however a vehicles fuel economy system doesn't take practicality or feasibility into account.
So IMHO I would say that perhaps 2500rpm would be more appropriate here, but not necessarily more economical. Plus at 2500rpm you are more in control of the vehicle, in the sense that it wouldn't just be labouring its way along the road with only poor acceleration and engine braking available to you.
