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Jeep Wrangler YJ
YJ General Discussion
Better gearing for the 2.5?
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<blockquote data-quote="machoheadgames" data-source="post: 441969" data-attributes="member: 18789"><p>I would highly suggest scrapping this idea and possibly recommend going the opposite direction with smaller tires and higher (stock) rpm. Taller gearing/lower rpm often does not equate to better fuel mileage. Fuel mileage is tied directly to load, which is how much throttle you need to overcome the load and keep the vehicle moving. In many cases, the lower gearing is better because you need less pedal to maintain speed, despite the higher rpm. You most likely would not see an mpg increase going to 3.55 or 3.73, if you did it would be so minor that it would take an extremely long time to pay for itself. If you did not see an mpg increase, you would be kicking yourself for a now even more gutless setup.</p><p></p><p>60s and 70s vehicles are not really relevant. Things were different back then, V8s were often the engine of choice and everything was carbureted. Almost nothing had overdrive and so tall axle ratios were the way things went.</p><p></p><p>You would actually probably get better mpg by going back to 205/75R15 or 215/75R15, despite that turning higher rpm than you're turning now. That was stock, after all. For the record, 3,000 rpm is not "screaming" either, unless a loud muffler is installed and making a bunch of racket. 3,000 isn't specifically sucking the fuel either, it might in some cases but some of my best mpg has been at 3000 around 65-70 getting 18-19 mpg.</p><p></p><p>Best thing for fuel economy is low speed, and small tires. 60-65 mph on a bone stock 4 cylinder would probably do 20 mpg easy unless something is wrong. But nobody wants to drive 65 (myself included). When you push 70-75, mpg drops off due to wind, not rpm. Wind is not linear, you get a lot more of it at higher speed and it really kills fuel usage unless the wind is pushing you.</p></blockquote><p></p>
[QUOTE="machoheadgames, post: 441969, member: 18789"] I would highly suggest scrapping this idea and possibly recommend going the opposite direction with smaller tires and higher (stock) rpm. Taller gearing/lower rpm often does not equate to better fuel mileage. Fuel mileage is tied directly to load, which is how much throttle you need to overcome the load and keep the vehicle moving. In many cases, the lower gearing is better because you need less pedal to maintain speed, despite the higher rpm. You most likely would not see an mpg increase going to 3.55 or 3.73, if you did it would be so minor that it would take an extremely long time to pay for itself. If you did not see an mpg increase, you would be kicking yourself for a now even more gutless setup. 60s and 70s vehicles are not really relevant. Things were different back then, V8s were often the engine of choice and everything was carbureted. Almost nothing had overdrive and so tall axle ratios were the way things went. You would actually probably get better mpg by going back to 205/75R15 or 215/75R15, despite that turning higher rpm than you're turning now. That was stock, after all. For the record, 3,000 rpm is not "screaming" either, unless a loud muffler is installed and making a bunch of racket. 3,000 isn't specifically sucking the fuel either, it might in some cases but some of my best mpg has been at 3000 around 65-70 getting 18-19 mpg. Best thing for fuel economy is low speed, and small tires. 60-65 mph on a bone stock 4 cylinder would probably do 20 mpg easy unless something is wrong. But nobody wants to drive 65 (myself included). When you push 70-75, mpg drops off due to wind, not rpm. Wind is not linear, you get a lot more of it at higher speed and it really kills fuel usage unless the wind is pushing you. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Better gearing for the 2.5?
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