Question by : Why Don’t They Have Huge Gears In Cars to Save Gas?
I don’t get it. I have a manual car with 5 gears, and of course in 5th gear, it cruises on the highway at the lowest RPM’s, and gets the best gas mileage. Why don’t they just make cars with 6th and 7th gears, and etc. so you can just keep shifting up and get better gas mileage. Is the gearbox not big enough? I don’t understand? Thanks
Best answer:
Answer by Zachary
The car companies are stupid and do what’s most cost-effective for themselves.
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The gears are chosen so the engine runs at its most efficient RPM at highway speeds of 55-65 mph. A higher gear wouldn’t be useful if you never go fast enough to shift into it.
The car need a certain amount of horsepower to go at that speed. That hp is determine by the aerodynamics of the car.
An engine generates different power at different rpms. If you want to maintain at 60 mph you will need about 30 hp. If you want to cruise at 1000 rpm to save gas, the engine will not be generate more than 30 hp at 1000 rpm to stay at 60 mph.
Not to mention real world need for parts to last 150,000 miles of abuse.
There are currently a number of manufacturers making cars with 6-speed manuals and 7 & 8 speed automatics.