Jeep Garage  - Jeep Forum

Jeep Garage - Jeep Forum (http://www.jeepgarage.org/forums.php)
-   Grand Cherokee - WK2 - (http://www.jeepgarage.org/f73/)
-   -   WK2 Hemi vs V6 MPG Compilation (results inside) (http://www.jeepgarage.org/f73/wk2-hemi-vs-v6-mpg-compilation-results-inside-24826.html)

Jeremy1983 06-23-2011 04:35 PM

WK2 Hemi vs V6 MPG Compilation (results inside)
 
So when deciding on which engine to order with my 2012 Overland, I decided to compile a spreadsheet that consists of the reported MPGs from individuals who posted in the various WK2 MPG threads on this forum and others.

Upon completion, I figured Id share my result with you all. The combined figures are NOT calculated from averaging the City and Highway, but rather from posters specifically stating their combined MPG. Also, I did not differentiate between 4x4 and 4x2.

Hemi MPG:

Avg. City: 13.8
Avg. Highway: 18.6
Combined Hemi: 15.8

V6 MPG:

Avg. City: 16.4
Avg. Highway: 23.0
Combined V6: 18.9

V6 MPG Advantage:

City: +2.6
Highway: +4.4
Average: +3.1

Richl 06-23-2011 04:56 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
I have the 5.7 and I get 15mpg city and up to 22.7 hwy, driving the Limited 4x4

Richl

1200RT-P 06-23-2011 05:37 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by Richl (Post 436511)
I have the 5.7 and I get 15mpg city and up to 22.7 hwy, driving the Limited 4x4

Richl

How? I hate to say it, but I don't buy it. Unless you're on flat ground with a tailwind every drive .....

My MPG is much closer to what's quoted in the first post. And this is normal city driving - "auto" mode, etc.

lll2for3lll 06-23-2011 05:48 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by Richl (Post 436511)
I have the 5.7 and I get 15mpg city and up to 22.7 hwy, driving the Limited 4x4

Richl

I believe it. Friend of mine is getting 15 with the 5.7 WK2.

ColdCase 06-23-2011 05:59 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
I dunno, I'm easily getting over 16 in Boston, and 19 during rush hour highway, and 21 highway without much traffic. I routinely average over 19 mpg over an entire tank of mixed driving, more or less depending on the ethanol mix. Perhaps driving style and anticipating traffic patterns?

What brand of kerosene... errr.. fuel are you low mileage guys running? I've heard that Cal gas is crap. I rented a car in SD recently and was amazed how much fuel it burned through.

Meso 06-23-2011 05:59 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by 1200RT-P (Post 436531)
How? I hate to say it, but I don't buy it. Unless you're on flat ground with a tailwind every drive .....

My MPG is much closer to what's quoted in the first post. And this is normal city driving - "auto" mode, etc.

I think aside from terrain, driving style has the most to do with the mileage numbers. I drive 45 miles per day all week. Of that about 15 is suburban City traffic and 30 is 70mph interstate. I average 18.5 consistently. Straight all City is around 15 and typical all highway miles in flat terrain is about 22.5. All within the EPA range of mileage estimates.

Caveats: I have a knack for catching green lights and I don't drive aggressively, mild acceleration in the City. Not a lot of hills or anything to deal with.

jgc4ever 06-23-2011 08:25 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Don't forget the 2012 5.7L V8 Hemi has a 6 speed transmission so mpg will likely improve.

jeepin dave 06-23-2011 09:12 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
I do not know if the following applies.
When I learned to fly from an old bush pilot, he said that to properly break in a piston aircraft engine, one had to fly at full power part of the time. He said this properly set in the components. His expression was to fly b*lls to the wall.
Otherwise one would get less mileage and lower performance.
Could something like this help explain the difference that people are getting?
Dave

Bmwister 06-23-2011 09:29 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by jgc4ever (Post 436599)
Don't forget the 2012 5.7L V8 Hemi has a 6 speed transmission so mpg will likely improve.

Adding more gear ratios does not automatically equal better fuel economy. We are already at 1500-1800rpm for typical highway cruising speeds. Lower than that would likely gain nothing measurable.

If the lower gear ratios are changed it MIGHT help the city cycle MPG, but not the highway MPG because the WK2 requires X-amount of horsepower to maintain highway speed (let's say it's 30hp at 65mph). Whether it makes that horsepower at 1800rpm or 1300rpm, it still needs to generate that (est.) 30hp to cruise on level ground and making 30hp costs a specific amount of energy. If you have to make 30hp at a higher rpm, you do lose fuel economy from the extra frictional losses than if you made it at a lower rpm. Aerodynamics has a far more dramatic impact on fuel economy for highway MPG. Weight has a more dramatic affect on city MPG.

The major affect from adding gear ratios and lowering rpm is to reduce the engine's rotational and reciprocating frictional losses which can improve economy...but only to a point. The issue is, the lower you go (rpm) the less of an economy improvement achieved until too low of an rpm actually reduces fuel economy due to the transmission continually downshifting to maintain speed against wind and roadway effects that may require 100-200hp for a short period. It is fine engineering "art" to perfectly match engine powerbands to transmission ratios to maximize the performance/economy envelope.

Engines need to turn at least 1500rpm on the highway (IMHO) in order to maintain sufficient oil pressure and coolant flow. If you turn the engine too slow, it puts a strain on the lubrication and thermodynamics. That is one reason manual transmission drivers are taught not to "bog" the engine. That's my old school two cents, anyway.

jgc4ever 06-23-2011 09:33 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
You know a lot about it. I was just thinking dropping down to 1500 rpm in 6th on the interstate going 75-80 mph could be helpful to mpg. Wouldn't apply to everyone and if it did would only be on those occassions where you're cruising at that high of speed though.

vikingdave 06-23-2011 10:00 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by 1200RT-P (Post 436531)
How? I hate to say it, but I don't buy it. Unless you're on flat ground with a tailwind every drive .....

My MPG is much closer to what's quoted in the first post. And this is normal city driving - "auto" mode, etc.

I routinely get 21 or 22 on the highway with my Hemi as well, cruising at 82mph in almost no traffic with the cruise control on. It seems counterintuitive, but the Hemi loves to be at the high end of "ECO" mode, cruising at high speeds on four cylinders. At that speed, I believe that it gets better MPG than the V6.

1200RT-P 06-23-2011 10:06 PM

Re: WK2 Hemi vs V6 MPG Compilation (results inside)
 
Quote:

Originally Posted by vikingdave (Post 436651)
I routinely get 21 or 22 on the highway with my Hemi as well, cruising at 82mph in almost no traffic with the cruise control on. It seems counterintuitive, but the Hemi loves to be at the high end of "ECO" mode, cruising at high speeds on four cylinders. At that speed, I believe that it gets better MPG than the V6.

I was discussing city MPG.


All times are GMT -5. The time now is 01:47 AM.

Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community