Libs sweet speedo spot

musclezmarinara · **Posted:** Sun Feb 26, 2012 4:51 pm

So did a weekend trek out to PA this weekend about 300 miles round trip.

Been trying to see the sweet spot for the lib with these diesel falken mountains on it.

Heading out was using cruise about 65 68 70 ish, lots of down shifts at that speed for the 140 mile one way I used just under 13 - 15 gallons around the 1/4 tank mark.

En route homeward to NJ been staying consistent On cruise at 76 78 mph lots less downshifting truck is staying nice in that range only driven about 50 miles in the trip at about 7/8 tank. Will update upon arrival home base.

Wondering if anyone has found similar results ? These falkens are heavy but seem to be efficient .

Appreciate the feedback keep wheelin fellas !

Musclez Marinara
Marco@acor4x4.com

lfhoward · **Posted:** Sun Feb 26, 2012 7:29 pm

I have a stock '08 Libby with A/T tires and a Scangauge II. In December I took a trip from Philly to Michigan and I tried to find the sweet spot. I experimented as I went, and I found there are so many variables that affect mpgs, and very small changes in the gas pedal can make a big difference! Crosswinds, tailwinds, headwinds that all change from second to second, blowback from passing cars and trucks changes your mpg's, not to mention going up and down long gradual hills. That said, I figured out that I got the best mileage (21-22 mpg) on the flat in Ohio at speeds between 55 and 65 mph, with not much difference in mpg between 55 and 65. At 55 it downshifted a little too often when climbing steeper hills, but I didn't notice a problem with that at 65 mph. The 3.7 L engine seemed comfortable there. I noted a 2 mpg decrease (19-20 mpg) when cruising at 70 mph, which means the engine has to work that much harder to keep the Jeep at 70 than at 65. The decreased mpg's must be because wind resistance increases exponentially with speed. I haven't tried it, but I think cruising at 75+ would eat into mpg's further.

Here's a fun fact: I averaged 24.4 mpg on an entire tank of gas driving back east with a tail wind and staying 3 seconds behind semis going 65 mph. That was my best tank to date, according to Fuelly.com. Please don't draft trucks on the highway, as this can be extremely hazardous to your health, but even following one at a safe distance has positive effects on your mpg's, because they help push the air ahead of you. But these days I'm lucky to get 14 mpg in the city while commuting to work. :-)

musclezmarinara · **Posted:** Mon Feb 27, 2012 9:38 am

Great explaination bud thanks !

jeeplikens · **Posted:** Thu Mar 08, 2012 12:32 pm

I drove about 30k miles in one year between Detroit and Chicago. Sometimes, 3 times a week. I found as long as you keep you RPM below 2k, your doing good. I don't have the hills or grades like in PA but I found that at 18-19k RPM (around 63-64mph), I could get 26.7mpg. Now, I had a K&N airfilter and stock tires. No A/C running and it was warm and sunny. On a return trip, 26.0 but had rain and was cooler with some cross winds. City, slow take offs, and slow slowdowns before reaching a light neted me 17-18 city. It's hard to follow the same tatics in the city but highway, just don't be in a hurry and you can get some decent MPG. I normally got 22 but that was driving 75-80. Over 80, it doesn't matter, it's still not going to be good. The worst I got was 19 but conditions doesn't matter when it's that bad. :oops:

Now, since then, I've added full skids (except gas tank). Added KK-SL2's from JCR offraod

,
roof rack with crossrails that I never take off, bug sheild and class III hiden-hitch with one of these stickingout the back

so, right now, I'm at 21hwy, 14city. I just got my 60k service done and had platnium plugs installed and the garage said it was burning a little rich. Throtle body was pretty dirty too. I know I'm getting better because I filled it up. drove 50 miles and I still show full (didn't fill up the neck either). I'll be happy with near the EPA rating. I need to burn through a few tanks before I get a good reading. Oh, and I have 235/70/16's A/T's for tires so I'm up one size from factor default.

tjkj2002 · **Posted:** Thu Mar 08, 2012 12:45 pm

jeeplikens wrote:

I just got my 60k service done and had platnium plugs installed and the garage said it was burning a little rich. .

Better turn right around and go back to that shop and have them install the correct plugs in your 3.7.You will do alot better with copper core plugs then platinums which cause issues in the 3.7.

lfhoward · **Posted:** Thu Mar 08, 2012 1:57 pm

jeeplikens wrote:

at 18-19k RPM (around 63-64mph), I could get 26.7mpg. Now, I had a K&N airfilter and stock tires. No A/C running and it was warm and sunny. On a return trip, 26.0 but had rain and was cooler with some cross winds. City, slow take offs, and slow slowdowns before reaching a light neted me 17-18 city. It's hard to follow the same tatics in the city but highway, just don't be in a hurry and you can get some decent MPG. I normally got 22 but that was driving 75-80. Over 80, it doesn't matter, it's still not going to be good. The worst I got was 19 but conditions doesn't matter when it's that bad. :oops:

Wow, that's awesome mileage. I have a trip to Michigan coming up and I'll see what happens when I set the cruise to 63/64 mph. Anyone else running a K&N filter see a 4 mpg jump in gas mileage on the highway?

jeeplikens wrote:

so, right now, I'm at 21hwy, 14city.

This is more like what I'm getting now. I have normal sized A/T tires, but other than that everything is stock.

lfhoward · **Posted:** Sat Mar 10, 2012 9:40 pm

jeeplikens wrote:

I found that at 18-19k RPM (around 63-64mph), I could get 26.7mpg.

I drove to Michigan today and I tested your theory. :JEEPIN:

You're right on; I got the best mileage on the flat with the cruise set at 63. In my case, best mileage was 23-24 mpg. Mpgs were slightly lower when driving at 62 and 64 mph, according to my Scangauge. I could get 23-24 mpg at higher speeds if I followed trucks (3 seconds back for safety), but I was pretty surprised how well I could do on my own with just keeping the speed at 63. Thanks for the tip! :rockon:

musclezmarinara · **Posted:** Sun Mar 11, 2012 12:00 am

63 it is thanks guys!

Musclez Marinara
Marco@acor4x4.com

lfhoward · **Posted:** Wed Mar 14, 2012 9:11 am

Following up: southern MI to western PA, cruise set at 63 = 23.6 mpg. I think I could have had 24+ mpg from this tank if it had been all interstate, but there was about 2 hours of 55 mph two-lane roads also on this tank.

Budke · **Posted:** Wed Mar 14, 2012 11:24 am

In my old 02 kj I got the best mpgs at 71mph.

Sent using the force

cybertron · **Joined:** Fri Feb 12, 2010 2:32 pm **Posts:** 72

Good grief, 26 mpg only happens in my dreams.

I got 23.3 on my last fillup and was tempted to throw a party. That was pretty much all at 60 mph with a few slowdowns for small towns. It's the first time I've gotten over 23 without some big caveats - the only other time I did it was a one-way trip, so wind, elevation, and gas pump differences were in play. This time it was round-trip to the exact same pump so except for wind everything should have balanced out. The weather right now is pretty much ideal for mileage - much cooler and I struggle to hit 22, ditto for much warmer due to AC use.

E2 · **Posted:** Mon Mar 19, 2012 12:08 am

I get 18 on the highway with my tires and lift with cruise control on at 65mph

Budke · **Posted:** Mon Mar 19, 2012 7:40 am

Set cruise at 71 and see what you get. I was getting 27mpgs with a 2.5 lift and 225/75 tires cruising that speed.

Sent using the force

E2 · **Posted:** Mon Mar 19, 2012 9:39 am

Budke wrote:

Set cruise at 71 and see what you get. I was getting 27mpgs with a 2.5 lift and 225/75 tires cruising that speed.

Sent using the force

Next long trip. Is that true 71, as when my speedo says 65 my gps says 71. I use my gps as my indicator now as if I go 60 based on my speedo I am going 65.

Budke · **Posted:** Mon Mar 19, 2012 11:31 am

True 71. My speedo was correct, it matched my gps speed. I would always set it there and leave it unless I had to slow down. Having to constantly accelerate and decelerate is what kills the mpgs so I try to avoid it as much as possible.

Sent using the force

lfhoward · **Posted:** Mon Mar 19, 2012 3:38 pm

Ok, so the GPS says your true speed is 71, but the trip odometer is tied to the speedometer that says 65. I'm wondering how did you calculate the 27 mpg figure? If you divided gallons of gas at fill-up time by the number of miles on the trip odometer, it's probably going to be an overestimate because the speedometer is off. If you could have your gps keep track of true miles driven for the whole tank, and divide that into the gallons of gas used at fill up time, that would be ideal. Not trying to find fault, just understand how you got 27 mpg.

27 is awesome, btw.

Budke · **Posted:** Mon Mar 19, 2012 4:12 pm

There's some formula I used in the yj was off but used the formula to get it. My kj was in sync with the speedo and I had an evic I used that gave me current mpgs and average. Average mpgs was usually 20ish but that's with mostly city driving. Best highway was 27 and that was a 2 hour road trip.

Sent using the force

racer1 · **Posted:** Mon Mar 19, 2012 8:59 pm

On my 08 73mph on the speedo gets the best mileage. 22-24.5 with cruise. Stock tires.

Dave

Smetna · **Posted:** Tue Mar 27, 2012 4:13 am

Drove for 8 hours from upstate NY to Roanoke VA. US15 and US81 most of the way.

When the speed limit was 55, I set her on 60. When the limit was 65, I set her on 65. For a brief stretch in VA, the limit is 70. I still kept her at 65.

I got 21.25 mpg.

So it would seem that the recommendations on here to go 63 or so are spot-on accurate. The sweet spot is around 60-65.

bily O · **Posted:** Sat Apr 07, 2012 11:36 am

you will get the best economy driving by the tac. insted of the speedo. try not to go over 3K on take off and 1.8K to 2.2K on the highway. its around 70 mph for my KK

Libs sweet speedo spot

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