Gas milage and drivability of 4.10 Rubicon gearing vs 3.45 Sport gearing

Zo6

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Took a drive today 200 mile round trip. Got 20.5 mpg. I have now 2600 miles on my Rubicon. I changed the oil and filter at 1050 miles using Mobil1 full synthetic and a Fram filter for synthetic oil. I also run Shell V-Power 93 gas. One happy Rubi owner! :rock::dance:
Good to know . I ordered JLUR
African or European?
Good to know . I ordered a JLUR 3/19 in D 1.





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JeepFan

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"gearing is going to reduce your mileage by about 19% (cuz 4.10 / 3.45 = 1.19). In other words, the engine is going to have to spin 19% more than 3.45-equipped JL to go the same distance."

Is this actually correct? I don't understand mechanics. Does fuel consumption increase linearly with engine RPM as gearing changes? If I downshifted a bicycle so that I had to pedal twice as fast to maintain the same speed, I would not be working twice as hard, I don't think, because I would do less work for each rotation. Doesn't the same apply to vehicles?
I agree, there wouldn't be a perfectly linear relationship between engine speed and fuel consumption - way too many variables involved. In fact increasing RPMs might actually improve mileage under some "lugging" conditions - depends on load, ground speed, gear ratio selected, headwind, etc.
 

ryandamartini

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I have a JLU Sport S with the Automatic. with two tanks of gas through it with no highway driving yet except one burst to go up to the mall, I'm averaging 19.6 in the city. I expect 22-25 on the highway easy.
 

intentsrig

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My 35's go on friday. JLU Sport with manual transmission. Interested to see how it will feel compared to my old 2 door JKR with the 3.8L motor

We shall see how much the MPG changes
 

Holymoly1963

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Gearing aside, the Rubicon weighs what, 250 lbs more than the Sahara, and a lot of that is unsprung, so it's even worse than that as it relates to fuel economy in the city.

BSG on the 2L turbo and '19+ V6 will help a lot with MPG. I had an F30 BMW 3-series that was a pseudo mild hybrid system (only 12V and no motor, but it had a high-current alternator that was smart enough to kick in when coasting downhill or braking), and I got insane mileage on the highway (43 mpg one 100 mile trip). iDrive would tell you how much energy was recovered by the system as you drove, and it wasn't insignificant. 48V and a true motor/generator should be quite impressive.
BMW really knows how to make engines. Not so sure Jeep is in the same league. I remember watching a YouTube video of the assembly of the 3.6 Pentastar and it opens with a strong woman flinging a new block from one spot to another on the assembly line as if it were a piece of firewood. Ouch...Personally I'm glad they are now made at a different plant. I've driven BMW's for almost 16 years and their engines are in a class of their own. BTW, I'm sure that 3.6 video is still out there.
 
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Jeepmarkjl

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Took a drive today 200 mile round trip. Got 20.5 mpg. I have now 2600 miles on my Rubicon. I changed the oil and filter at 1050 miles using Mobil1 full synthetic and a Fram filter for synthetic oil. I also run Shell V-Power 93 gas. One happy Rubi owner! :rock::dance:
how it on highway driving. A fight? A wrestling match? or smooth?
 

Jeep4Life

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how it on highway driving. A fight? A wrestling match? or smooth?
On a nice day it’s smooth. I did take a trip to Florida and it was very windy the whole trip down and I couldn’t go over 70 mph or it was a wrestling match. So as long as you don’t have gusting winds it’s amazing! I love my Wrangler more everyday. Almost 3000 on it now and still getting between 19.9 and 20.5 mpg. ;):rock::clap::dance:
No regrets at all! :jk:
 

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My JL Sport S is averaging 21.3 doing a 50/50 split of city and highway. The only way to know the difference between this and a Rubicon would be for me to spend a month driving a Rubicon on the same daily circuit to and from work.

However, based on my 23 years of experience with trucks and SUVs I would guess that the axle ratio, small increase in height, and tires on the Rubicon would subtract about 2 MPGs from it's average over a Sport model, assuming both are stock. This would put the Rubicon at around 19 MPGs average for me, which actually lines up very well with what a lot of guys are reporting.

For the average U.S. driver at current prices, 1 MPG = ~$15/month.

So, the fuel costs on a Rubicon are going to average about $30/month more than a Sport.
 

Bluegoose972

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Running 37's on my JLUR and getting 15.5-16 MPG around town and 18 on the freeway, if I don't push it. JLUR really isn't liking speeds above 65 mph with the current gear setup. Sure it will go faster, but the transmission drops the RPM's down far enough that the drivetrain stuggles to maintain speed and is constantly searching between gears 6-8. If I just slow down a little (normally that guy that drives 5 MPH over the speed limit which puts me at 75-80 mph) and enjoy the ride and stay around 65 mph, the gas mileage stays up in the 18's. But push it and my mileage drops down to 13 mph (found this out on my first trip home of 170 miles....was fighting some wind too).
 

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For me, the Rubicon will provide more smiles per gallon. :)
 

xeon

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35" on lifted JLU Rubi -automatic

I started tracking MPG the day I purchased it in April, not as away to see if I could reach the 20 MPG that had been advertised but to know when the engine was starting to break in properly and when I had been able adjust my driving habits.

- after 3000 miles... I am averaging 19.5 on highway if I remain vigilant about conserving fuel. Most of this particular driving has been up and down the 10 freeway in So Cal with average speeds between 60-70MPH with three adults and with minimal load. Staying in the slow lanes. Coasting as much as possible. Now if I just get it the darn thing and drive the way I would normally, 70-75mph and not worrying about coasting and keep up with the normal traffic flow that milage will drop to between 16-17 mph.

I have noticed that on flat surfaces to maximize fuel efficiency I am best between 60-65 mph when in 8th gear. However, I can also get good mileage in the city if I stay in 5th gear between 45 and 50.

Now the annoying thing for many is the auto start/stop. But to achieve 19.5...i have to leave it on and actively engage it if I hit bumper to bumper traffic. its really easy to light break and creep and not engage it but those small start/stops add up over a week and make the difference between 18.8 and 19.5 mpg.

Mileage does also vary with hardtop vs soft top. My first 2K miles were done with the hardtop and I was able to reach 20.1 average MPG. Keep the windows up or your milage will drop a tad. When I switched to the soft top there was a significant and noticeable difference I was not expecting. I thought with the difference in weight the milage might go up slightly. It actually went down slightly to where I am now at 19.5 if you keep the windows rolled up. As soon as you roll down the driver and front passenger windows....you get an amazing parachute effect and mileage will drop significantly. I found it to be between 17.5 and 18.5. Remove the rear window and you get back to 19.5.

Anyway...all fun and games at this point. Once summer hits and the mornings are about 75 the top will be down most of the time and I will get a gauge on the MPG then. But like WXman said, the subtle difference in MPG are not why you buy a Rubicon over a Sport, at least not for me. The buying decision was what I was going to do with it and what starting point I wanted to start modding it at. Sport...low initial cost...lots of mods for me to make. Rubi - higher initial cost and less mods for me to make. In the end its a personal decision .... no wrong decision. Its a JEEP....run over stuff ... have fun.
 
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intentsrig

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My 35's go on friday. JLU Sport with manual transmission. Interested to see how it will feel compared to my old 2 door JKR with the 3.8L motor

We shall see how much the MPG changes
Hand calculations put me at 14.3-14.5 mpg for last three fill ups. All city driving. Suprisngly the computer is not far off. 4.88’s will help bring the mpg back up.
 

GARRIGA

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Hand calculations put me at 14.3-14.5 mpg for last three fill ups. All city driving. Suprisngly the computer is not far off. 4.88’s will help bring the mpg back up.
If 4.10a roll 33 getting x mpg than going to 35 and staying at same 4.10s decrease mpg that dramatically causing the need to get 4.88s?

I want 37s but was contemplating 35s through the warranty period to avoid major expenses such as new gears. Figured with 37s I’d have no choice but to get new gears. If I’m forced to do that I’m back to going 37s or living with 33s.
 

RubenZ

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The bigger question is how do you want it to drive while in 4wheel Drive? Do you want the lower gearing of the Rubicon Transfer Case or the higher gearing of the Sport/Sahara?
 

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