Does Part Time in a 80 = better MPG? - You be the judge
- Thread starter LandCruiserPhil
- Start date
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I can regularly achieve 14.5 - 15 mpg on combined stretches of long uphill and long downhill when the net elevation change is a significant loss as in your case.
Your first leg from Moab to Flagstaff has a 2,500 ft. elevation gain, and it appears you were not driving extensively at 70+ mph given your average speed. I typically end up between 13.5 and 14 mpg in these conditions, although if I want to cruise consistently over 70 mph that will drop to around 12.5.
Your second leg is from 7,000 ft. down to close to sea level. On my last trip from Winter Park to Denver, which is 8,600 ft over a 12K ft pass and then down to 5,500 ft (with some additional large ascents/descents) I averaged 17.5 mpg. The climb back to 7,400 ft. to my house from Denver reduced total trip economy to exactly 15 mpg.
I had four kids, two large dogs, a completely loaded roofrack and all the other good stuff from a week long ski trip onboard. Highway speeds of 65-70, average trip speed given the pass speeds was ~55. 37" tires, 5.29 gears, AWD.
So no, I don't think it improved your fuel economy, but I'm glad you felt like it did because seat of the wallet results are always important for the first few months after you complete them
Your first leg from Moab to Flagstaff has a 2,500 ft. elevation gain, and it appears you were not driving extensively at 70+ mph given your average speed. I typically end up between 13.5 and 14 mpg in these conditions, although if I want to cruise consistently over 70 mph that will drop to around 12.5.
Your second leg is from 7,000 ft. down to close to sea level. On my last trip from Winter Park to Denver, which is 8,600 ft over a 12K ft pass and then down to 5,500 ft (with some additional large ascents/descents) I averaged 17.5 mpg. The climb back to 7,400 ft. to my house from Denver reduced total trip economy to exactly 15 mpg.
I had four kids, two large dogs, a completely loaded roofrack and all the other good stuff from a week long ski trip onboard. Highway speeds of 65-70, average trip speed given the pass speeds was ~55. 37" tires, 5.29 gears, AWD.
So no, I don't think it improved your fuel economy, but I'm glad you felt like it did because seat of the wallet results are always important for the first few months after you complete them
- Thread starter
- #3
I can regularly achieve 14.5 - 15 mpg on combined stretches of long uphill and long downhill.
Your first leg from Moab to Flagstaff has a 2,500 ft. elevation gain, and it appears you were not driving extensively at 70+ mph given your average speed. I typically end up between 13.5 and 14 mpg in these conditions.
Your second leg is from 7,000 ft. down to close to sea level. On my last trip from Winter Park to Denver, which is 8,600 ft over a 12K ft pass and then down to 5,500 ft (with some additional large ascents/descents) I averaged 17.5 mpg. The climb back to 7,400 ft. reduced total trip economy to exactly 15 mpg.
I had four kids, two large dogs, a completely loaded roofrack and all the other good stuff from a week long ski trip. Highway speeds of 65-70, average trip speed given the pass miles was ~55. 37" tires, AWD.
So no, I don't think it improved your fuel economy, but I'm glad you felt like it did because seat of the wallet results are alway important for the first few months after you complete them
That is great you get mileage you claim. Re-read my post, I dont care at all about mileage I did for part time not for gas savings, my post was information purposes only.
Sounds like a tuned fj. I get just over 14 avg. and 16-17 peak on long trips. Anybody not getting this has work to do or they drive with a heavy foot all the time.
I get 10-12 MPG all the time. I did a complete tune up to. I dont know how you guys are getting 14-16 or 17. To get 12 i have to drive like a 80 year old women.
- Thread starter
- #7
I know, I was just being the judge
Thanks you for your input. Im sure other would like to hear more on your technique in order to achieve that kind of mileage consistently. With 37's and 5.29s gears can you pull hills at the posted speed and still get those numbers?
To add more info I tend to drive with the no pass style. I try to run at the posted speed limit. With stock gears I find my rpms at 4000 rpm on steep hills with peaks up to 4500 at time. Without gears I find this necessary.
You would want the information to be valid and significant, no?
To do so you would need to run the same course under the same carefully controlled conditions with a more accurate means of determining the fuel used to get an accurate comparison.
Otherwise, you would need to make many measurements with and without full time 4wd to be sure you have a statistically significant difference. Excel has a statistical package built in.
- Thread starter
- #9
Your point makes perfect sense. It did give me something to do driving home solo.
FWIW I didnt see any noticeable change when I did it several years ago either.
a tale of mileage
Mileage is a tricky thing. Controlled conditions are indeed the best way to resolve the matter.
As an example, after changing my 96 FZJ80 (OME lift, ARB bull bar winch) from 18x8 wheels with BFG LT 285/65R18 to 2010 FJ Cruiser wheels (16X7.5) with BFG 265/75R16 my mileage improved. Haullng 3300 lbs of old wheels and tires in back I filled up in Ashland and cruised up Oregon 66 to Tulelake, CA, averaging about 40-50. A climb of about 2500 feet. Then down California highway 97 (averaging about 55-60 ) back to Yreka, CA where I filled up again. Mileage 17.1 MPG! My best ever.
However last week I took a friend from Happy Camp to the White City Oregon Veterans rehab center (300 mile round trip). We averaged 50-55 on the river road and 65 on the interstate. We also drove through about 10 miles of moderate traffic. Before and after fill ups came out to about 14.5 MPG. There is one good pass at about 4400 feet and I just let the cruise control take it up and that may have cost some.
Will try the White City run again at lower speed see if I can get back my 17 MPG.
Mileage is a tricky thing. Controlled conditions are indeed the best way to resolve the matter.
As an example, after changing my 96 FZJ80 (OME lift, ARB bull bar winch) from 18x8 wheels with BFG LT 285/65R18 to 2010 FJ Cruiser wheels (16X7.5) with BFG 265/75R16 my mileage improved. Haullng 3300 lbs of old wheels and tires in back I filled up in Ashland and cruised up Oregon 66 to Tulelake, CA, averaging about 40-50. A climb of about 2500 feet. Then down California highway 97 (averaging about 55-60 ) back to Yreka, CA where I filled up again. Mileage 17.1 MPG! My best ever.
However last week I took a friend from Happy Camp to the White City Oregon Veterans rehab center (300 mile round trip). We averaged 50-55 on the river road and 65 on the interstate. We also drove through about 10 miles of moderate traffic. Before and after fill ups came out to about 14.5 MPG. There is one good pass at about 4400 feet and I just let the cruise control take it up and that may have cost some.
Will try the White City run again at lower speed see if I can get back my 17 MPG.
Alluding to murf's post:
What was the cost to fully convert over to part time (parts and any labor you paid)?
I know you didn't swap over with the intent of improving mileage, but it may be good information for people who are interested in doing this for economy reasons. Knowing the real world numbers may be surprising to some.
What was the cost to fully convert over to part time (parts and any labor you paid)?
I know you didn't swap over with the intent of improving mileage, but it may be good information for people who are interested in doing this for economy reasons. Knowing the real world numbers may be surprising to some.
Unless I missed something in that post, there is nothing on which to judge whether a part time kit has any effect on gas mileage. Do you have any records of the same drive in Fulltime 4wd in your truck, prior to modification?
This is a funny - beat to fricken death subject. These trucks suck wind on the gas mileage front. And I mean sssssuuuuuCK as Ron White would say!
My Ford Excursion gets the the same mileage as the Landcruiser - all 8,000#, lift, big ass tires, 400 HP, 500 FT# torque V10 and all. Pretty pathetic when you think about it. At least the Ford has a 45 gallon tank from the factory.
My Ford Excursion gets the the same mileage as the Landcruiser - all 8,000#, lift, big ass tires, 400 HP, 500 FT# torque V10 and all. Pretty pathetic when you think about it. At least the Ford has a 45 gallon tank from the factory.
- Thread starter
- #14
The thread is kinda dumb...my fault. I have nothing to compare because I have never checked my MPG prior
I just posted so others can see what Im getting with my set-up.
I didnt do it for MPG reason I wanted and like part time 4WD.
I posted the cost on the link in the 1st post.
Total cost of the mod was $450 (transfer case parts and Aisin hubs only)
No labor cost of hubs or transfer case modification
No cost of birf seal kit or other consumables added in $450
No shipping from Australia for t-case parts - parts picked by CSC member
No machining of axle stub cost - provide by CSC member
No removal and pressing of transfer case bearing - provide by CSC member
No cost for CDL, switch required
It is entirely about the long descents, which don't have much to do with tire size or gearing - they simply take a really crappy base fuel economy and weight it favorably. Which by the calculations you posted is exactly what happened. Flagstaff to Phoenix is what gave you the good numbers - drive it the other way and you'll drop 1-2 mpg across the entire trip.
On long ascents, my 80 drives better with 37's and 5.29's than stock gears and 33's, and gets slightly better fuel economy. I have now owned two AWD I6 built 4x4's, and both times going one gear ratio lower than conventional wisdom paid dividends in fuel economy and on/offroad performance.
FWIW, on my old rig I installed lockout hubs, and the Jeep NV t-case had a part time setting as well as AWD. I never had any gains in fuel economy from any of the settings including part time (RWD) with the front hubs locked out - just like the 80, it was built on an I6 platform that was set up for low RPM work, and there ins't much you can do to make that better or worse except drive 60-70 mph instead of 70-80.
