15 USMPG highway? Not good!

andersoncol · **Posted:** Sat Jan 22, 2011 1:50 pm

On a recent highway trip, I got about 18 MPG (imperial) or 15 USMPG. Yes, it winter here in canada, but that is absolutely ridiculous. Other guys with liberty's around here are still showing high 20's to 31MPG(imperial). I took it into the dealership where they scanned for codes and said everything appears normal. I didn't have my new OTC Genisys scanner yet, so I figured I'd try the dealer. I got them to change the oil as well. So they say nothing's wrong. How can that be? I've changed the fuel filter, air filter, and cleaned the Map sensor. Any ideas?
My Liberty is a 2006 CRD with a 2.5" lift and a roof rack. I can see that the lift and roof rack would lower the MPG a little, but shouldn't be that much.

mikey1273 · **Posted:** Sat Jan 22, 2011 3:02 pm

mine was suffering with low MPG too my thermostat was not working right and may have been slowly failing for a while. I got it fixed last week with OEM parts now it comming back. I was getting in the area of 15-16 around town now its back to 18-19. it used to bw that for town driving in the summer but since the GDE tune city driving nets me about 21 MPG.

Check to see if you are getting up to full coolant temprature. if not that can be a small part of it. you can try blacking part of the Radator with cardboard. just need to change it someetimes and dont go in the car wash with it in.

Winter Diesel is blended with Kerosene so it won't Gell up that lowers the BTU or energy content of it meaning the engine used more to make the same power. nothing you can do about that but maybe move to southern California or Arizona.

andersoncol · **Posted:** Sat Jan 22, 2011 3:06 pm

I do have grille inserts that pretty much block all the air flow. I understand the winter diesel idea, but other CRD's are still getting high 20's and 30 MPG. I'll try my scanner on it later today to see what the engine temp is getting up to.

Joe Romas · **Posted:** Sat Jan 22, 2011 4:05 pm

How many miles? What weight motor oil? Tire pressure?

If your not running one mark below half way or better on the temperature guage that means your thermostat is bad and no amount of blocking air flow on the front will make a piddly difference in operating temperature :ALONE:

stoutdog · **Posted:** Sat Jan 22, 2011 4:11 pm

Definitely check the tstat. I've also heard of some people having problems with stuck brakes, so that may be worth checking too.

Joe Romas · **Posted:** Sat Jan 22, 2011 4:18 pm

A good sign of a struck brake is excess brake dust on one or more wheels :BANANA:

warp2diesel · **Posted:** Sat Jan 22, 2011 7:39 pm

Low tire pressure is one thing that will eat you alive in winter more than summer. I run 45 PSI (~3 bar) in my 215 85 R16 load range E tires. When I had the original crap 225 75 R16 tires, I ran 40 PSI. Many think that lowering the air pressure will add traction in winter because Grandpa told them so. All I can say their Grandpa was not Sir Isac Newton. If you have an aversion to Sir Isac Newton because he was a Real Scientist who happened to be English, talk to an Over The Road Trucker about tire pressure, the OTR trucker will tell you the same.

Plugging in your block heater when you can in very cold weather will also help fuel economy.

I have the area behind the grill covered with cardboard, but that only blocks 2/3rds of the radiator, the rest of the radiator gets its air from under the front bumper.

Is your problem when it is colder than -23C (-10F) if so, you are luck to get 15USMPG unless you are going on a long express way trip. Driving around town kills mileage more in the very cold winter than moderate summer.

ATXKJ · **Posted:** Sat Jan 22, 2011 8:38 pm

Engine Temp should be within a tick or two of 12:00,
if it in the 1/4 range - the thermostat is dead

woodtick · **Posted:** Sun Jan 23, 2011 3:04 am

i CHANGED MINE TODAY sorry caps locked. I hope mine gains the mpg's it usually has

andersoncol · **Posted:** Mon Jan 24, 2011 8:30 am

Joe Romas wrote:

How many miles? What weight motor oil? Tire pressure?

If your not running one mark below half way or better on the temperature guage that means your thermostat is bad and no amount of blocking air flow on the front will make a piddly difference in operating temperature :ALONE:

144,000 KM, 5w40 rotella sythetic, I think 40PSI on the tires. I tried to hook up my new $2700 OTC Genisys to it yesterday, but it couldn't connect for some reason. Checked #33 fuse and it was good. Temp gauge shows one to 2 bars from 12:00. I'll have to watch it more intently when I drive it next.
I don't see any evidence of a stuck brake, and the MPG number I showed was on a highway trip in the -20 degrees celcius range.

Joe Romas · **Posted:** Mon Jan 24, 2011 12:56 pm

Yesterday at 12f it took my transmission 4 miles to warm up enough to lock the torque converter :dizzy:

I suspect it's much colder up there and wonder if the torque converter is ever locking up :?:

TJ2 · **Posted:** Tue Jan 25, 2011 5:33 pm

I wonder about the effects of the lift and roof rack. GDE say to expect 3 to 4 mpg loss with a lift. I would expect the drag of a roof rack to increase that.

How good were your mpg at their best WITH the lift and rack in place. I'd don't imagine I'll ever see the high 20's. Guys who get that seem to have their rigs set up for highway mpg. . . not for offroad. Check out the CRD's in your area. What kind of rubber and what are the owners' driving habits.

YMMV (I guess it has already)

andersoncol · **Posted:** Tue Jan 25, 2011 10:16 pm

I bought it a couple months ago with lift kit and roof rack already installed, so nothing I can go back on for previous numbers. The 15 USMPG was the best run I've gotten. I seem to only get 400-450 km to a tank of fuel. Another guy with a stock one says he is getting 31 Imperial MPG. And that was only a week or so ago.

warp2diesel · **Posted:** Wed Jan 26, 2011 7:36 am

How cold is it up there? -40 (C and F are the same at that temp)
Is your air cleaner clogged up with snow?
Is your air filter element iced up and not had a chance to thaw out?
Some of us put the lower half of a V6 air box on to keep the air filter from packing with snow or getting wet in a hard rain. The V6 lower half of the air box moves the intake up to just below the hood instead of a straight shot from behind the grill.
What size tires are you running?
It makes a difference on tire pressure.
Do you have any chance to drive over 105 KMPH (63 MPH) so the trans can get a chance to shift into 5th lock? The VM engine likes to run under 2,000 RPM to get peak fuel economy with the F-37 TCM the engine never gets a chance to run at a good RPM.
Is Saskatoon rolling prairie or mountains?
Do you do a lot of short start stop trips or go for the long trips?
If you never get out of town, 15MPG in a cold winter is not great, but not that bad. Especially if you drive around a bunch of aggressive driving Toronto or Detroit transplants

andersoncol · **Posted:** Wed Jan 26, 2011 8:20 am

On that trip it was around -20 dgrees celcius. Air filter is clean and new, with no ice or snow in it. Running stock 235/65/17 tires with touring tire type tread.(not aggressive). Tire pressues were set at 35 at the tire shop. Saskatchewan is rolling prairie. mostly flat. I was driving between 100-106km/hr. The 15MPG was on a long trip, but it doesn't seem to make much of a difference on how many km I get to the tank. Obviously a bit better on the highway, but maybe only 50-75km more per tank. Now that I got my scan tool figured out, i'll have to take it with me next time I drive it to check the engine temp it gets to. I'll increase my tire pressure to 40PSI as well.

15 USMPG highway? Not good!

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