BJ42 fuel economy

[Roberto]

help! What can I do to make my BJ42 a little more economical on fuel? I was thinking of taking my 4:11's out for awhile and put 3.7's in since I drive a pretty good distance to work and back, would this make much of a diff? What application would work for mine BJ? Mine has the full floaters if that makes a diff? Is it an easy swap? I have a 5 speed tranny, 31 X 10.5 X 15 tires and seems like I am getting 12-15 MPG. Does that seem right? Of course I am doing 75MPH at 3000 RPM the whole time, so maybe that is correct? But really, will changing my diffs to the 3.7's do me any justice? I just got it so there are alot of bugs to work out I know, but this is my daily driver so I need to start on fuel. Any suggestion? Anything I can do to the tranny?

Roberto

 

[Lantec]

help! What can I do to make my BJ42 a little more economical on fuel? I was thinking of taking my 4:11's out for awhile and put 3.7's in since I drive a pretty good distance to work and back, would this make much of a diff? What application would work for mine BJ? Mine has the full floaters if that makes a diff? Is it an easy swap? I have a 5 speed tranny, 31 X 10.5 X 15 tires and seems like I am getting 12-15 MPG. Does that seem right? Of course I am doing 75MPH at 3000 RPM the whole time, so maybe that is correct? But really, will changing my diffs to the 3.7's do me any justice? I just got it so there are alot of bugs to work out I know, but this is my daily driver so I need to start on fuel. Any suggestion? Anything I can do to the tranny?

Roberto

Are you sure you're getting 12-15MPG??

http://oee.nrcan.gc.ca/transportation/tools/fuel-trip-calculator/fuel-calculator-input.cfm

next time you fill up, reset your trip and see how far you get on a tank.. then fill in the information on that site.

Also, check your tire pressure, do your regular maintenance. if it really is that bad, see if your brakes are sticking to the rotors/drums.

 

[Roberto]

I will do this, I did a fuel filter change this weekend, oil change with filter, flushed the radiator, air filter change, new belts, to be honest the vehicle sounds very abrasive besides the diesel itself. I was actually thinking maybe the sound was coming from the rear brakes, so I will check it out. I will check tires also. I cannot do anything about the speedo since it is cut in the rear. It took just about 2 tanks for a 480-500 mile trip? Thanks for your help.

Roberto

 

[David*BJ70]

I do 19 to 25 mpg (US). 3B, 5spd, 3.7 diff... depend of the tire size and outside temperature... and driving habbit !

I belive driving a 3B at 3000rpm is a bit to much... for the MPG. 2400rpm should be a better target.

Since your already make a full service to your Cruiser... put a good (and strong !) additive to your next tank. Check your tires pressur. Then, why not rebuilt your ingector.

... don't "downgrade" your diff. Buy bigger tire !

 

[eleblanc]

... don't "downgrade" your diff. Buy bigger tire !

X2...................

 

[crushers]

unless you are wheeling then the 3.7 is a great diff, you can get them cheap (i have 7 SETS for $100 each ($200 a pair)) if you do wheeling then maybe keep the 4.11 in.
there is a couple ways to do this, straight highway driving then stick in the 3.7 and done.
if you do light wheeling, i.e. no rock crawling then stick with the smaller tire and put a set of t/case low range 2.3 gears in. in low range you are back to just better than stock set up.
the down side of going taller tire is rolling resistance in stop and go traffic as well as minimal more wind resistance at speed... remember you are driving a brick.
the cheapest fix is to drive slower.
cheers

 

[jmylie]

Something is not right. A BJ42 should be getting over 20 MPG.

I would guess that you need your injectors cleaned.

I get 18 to 22 MPG with my HJ60 running 33 x 10.50's. My friend has a BJ46 with a 5 speed and 34 x 12.50 tires and gets similar milage.

12 to 15 MPG is 2F territory

 

[Green Lantern]

FWIW...

I put 33x9.5 tires on my BJ42 and switched the diffs to 4.11's. My speedometer is accurate with that combination but the odometer is about 15% off. When I check my mileage I divide the fuel used into a known mileage between cities. I'm getting around 22 mpg.
HTH
Happy Trails! N

 

[Roberto]

Thank you all. I plan on driving it daily for at least a year while I purchase all parts for a resto. I am checking the brakes tommorow and I will get the injectors cleaned as well and plan on putting an electric fan on to help fuel. I plan on on putting a 32" tire on but dont want a wide one, I actually like the look of the Dunlop Roadtrak Major if I can get them here to the states! I probably will put with you on the 3.7's crushers! Only thing I will probably ever do with this thing is pull a small trailer camping once I purchase one, hopefully a Canadian M101 soon so 3.7 gears should be fine? what is the book I need to keep an eye out for for my BJ42 as far as doing repairs and rebuilds? any certain manual?

Roberto

 

[ylexot]

I agree with most of these guys, 12MPG is ridiculously low.

75mph at 3500rpm with a 5spd and 33's doesn't compute. I have a 4 speed and stock tires which requires 3500rpm to go 75 -- not recommended.

Per your description you must have ultralow gears, on the order of 5.5 at the diffs. In that case 4.11s would make a significant difference.