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Old 03-28-2015, 09:11 AM
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Join Date: Oct 2012
Posts: 13
4.0 vs 5.3 LS3

Hello everyone, I have a 94 YJ with 4.0. I'm considering swapping in a 5.3 LS3. Presently I'm somewhat reluctant because the 4.0 runs real strong (pulls like a freight train) with over 197,000 miles on the odometer. I'm torn between a 4.0 stroker motor or a 5.3 LS3. My targets are improved torque and hopefully fuel mileage. I presently am averaging 13.5 to close to 15 mpg during normal daily driving. I would appreciate any advice from anyone who experience with this swap. I would be curious if the fuel mileage actually improved with the LS3 motor. Thank you in advance for your help, Ed B.

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Old 03-28-2015, 12:44 PM   #2
0III0forlife's Avatar
Join Date: Mar 2012
Location: Ridgway, Pa.
Posts: 4,757
I have been contemplating the 5.3L swap into my YJ as well.

A good friend and my off road club president has a 5.7L in his with a 700R4 auto behind it and he doesn't get good mileage with it at all. He is on 35" rubber and gets mid 12's to low 13's for MPG. Not that I am all that worried about fuel mileage, but, I don't want to have the need for Jerry cans just to go out and play for a day. He trailers his YJ to the places to play, where mine is still a daily driver.

'87 YJ, 4.2L built and bored, 8" of lift, 8.8 rear, AX15/NP 231J, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...
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Old 03-28-2015, 12:56 PM   #3
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Location: Cardiff By The Sea / Glamis
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Running 35's 13-14 mpg is going to be what you get with either the 4.0 or 5.3. I'm running a 4.0 on 35's with 4.56 gears and 13/14 is normal. I'd love a V8, but practically I'll probably go a stroker if the 4.0 ever decides to quit. It's at 230000 miles and still pushes the jeep at 70 mph without braking a sweat.
92 Jeep Renegade - 4.0, 5 speed with Borla headers, MSD wiring. Front Currie D44 with cromo and ARB, rear 8.8 with Yukon super 88 kit and ARB, 4.56 gears, 35x12.5 MTR Kevlar, 4.5 RE Extreme, Bilstien 5100, RuffStuff 1 ton over the knuckle steering, 9500 synthetic line winch, 52" LED light bar, GenRight skid plate.
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Old 03-29-2015, 08:31 AM
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Join Date: Oct 2012
Posts: 13
Thanks for your advice. I suspected the fuel mileage would be similar. I'm really leaning toward the stroker and your input confirms I'm heading in the right direction. I'm really impressed with the torque of the present motor and the fuel mileage is not that bad for a lifted Jeep with 4.56 gears, 35" mud tires and all the areodynamics of a brick. I also like the simplicity of the 4.0 motor which is a plus on a daily driver or on the trail.
Thanks again for advice, Ed
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