4LO VS 4Hi for gas mileage offroad

[chayos00]

Hey guys I was just curious if anyone has paid attention to this or not? While off-roading this weekend I noticed my truck was telling me I'm getting about 18.2mpg (computer) normally on-road my computer tells me anywhere from 25-27mpg. So obviously there is a good difference in gas mileage off-roading.

When I was in 4Lo the engine was usually turning a lower RPM due to the increase in torque (from tranny, not engine) vs while the truck was in 4hi it usually was turning a higher rpm like 500-800rpm higher. So theoretically in 4LO it should get better MPG due to a slower running engine, would I be correct?

I don't have much off-roading experience under my belt so that's why I question it. Plus now I see why people carry extra gas with them when they do off-road.

Also how many miles on a tank do people get when they off-road?


****Edit - I don't really care what mileage I do get while off-roading, I was just curious about other peoples observations. Don't make it too technical guys! This was just started out of curiosity.****

 

[4RBob]

for the same speed(mph) and the same transmission gear, 4Lo would be higher RPM's, not lower.

 

[chayos00]

for the same speed(mph) and the same transmission gear, 4Lo would be higher RPM's, not lower.

That would be correct, but since we have auto tranny's it would change the gearing. So with speed being the constant not the gearing then that's when I saw the lower RPM's.

My truck ran almost 1K-1.2K in RPM's (4LO), just cruising along, where 4hi it was more like 1.5-1.8K RPM's.

 

[4RBob]

just cruising along doesn't tell us a speed or a gear, but if you are cruising in let's say 2nd gear at 10mph, in theory, you would be running a higher RPM in 4Lo. however, since you can cruise more easily in 4Lo without "gassing" it to get/keep going, sometimes you will see higher rpms in 4Hi.

here's an online calculator that may help illustrate.

4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators

 

[GMZ]

4LO will disable OD right? So youd be in 4th instead of 5th for starters? RPM isnt the end all of efficiency, the load on the engine can change the mpg quite a bit.

 

[offshorebear]

MPG off road? Who knows, maybe 3 or 4 mpg? Very different then driving on pavement.

 

[03_4x4Runner]

I do not let gas mileage determine if I use hi or lo. The terrain does this. If it is rocky I use lo to creep along slow, I also use lo on steep grades to not over heat the transmission. In lo the 4runner climbs easily with very little gas and downhills the engine braking works great in lo. On smoother, longer trails I use hi because you can only go about 25 in lo without overevving the engine. I switch between lo and hi many times a day here in the desert.

 

[chayos00]

I don't really care what mileage I do get while offroading, I was just curious about other peoples observations.

 

[progress4m]

MPG off road? Who knows, maybe 3 or 4 mpg? .

for offroad 3-4 mpg sounds about right.

 

[scottm]

On my older Land Cruiser, the shift points change electronically when in 4LO: the engine revs higher for each gear. There is a mod for defeating that and a mod for not locking the center diff in 4LO. I'm surprised to hear the 4R shifts lower in 4LO, the opposite of the LC.

 

[gm350reratliff]

Hey guys I was just curious if anyone has paid attention to this or not? While off-roading this weekend I noticed my truck was telling me I'm getting about 18.2mpg (computer) normally on-road my computer tells me anywhere from 25-27mpg. ****

Wow how do you get this kind of mpg's? I thought I was lucky getting 20-21mpg.

 

[JB.]

Hey guys I was just curious if anyone has paid attention to this or not? While off-roading this weekend I noticed my truck was telling me I'm getting about 18.2mpg (computer)....

Based on a large sample of multi-day trips with a moderately loaded vehicle and tires about 20psi, my range with the V8 has been 8-13mpg (actual). It varies a lot depending on conditions (snow, mud), idle time (for heat), stuff like that, but in dry conditions and moderate weather with fairly light, low-range use, I expect to get 11 or 12mpg. Smooth dirt roads with highway tire pressures would obviously get considerably more. Even at 11, though, that's nearly 250 off-road miles per tankful so, as you can see, the need for extra gas doesn't present itself very often.

As far as mpg in lo vs hi, the question is mostly academic if you restrict low range use to the times when you need it. For the most part, being in high range would result in lower rpms at low speed and better mpg. It is possible, though, for low range to be more fuel efficient, for instance climbing a steep hill where 1st high would be revving higher than necessary and wasting energy in the torque converter.

 

[chayos00]

Wow how do you get this kind of mpg's? I thought I was lucky getting 20-21mpg.

My computer usually told me any where from 21-23mpg, equaling calculated MPG's of 19.X - 21.X MPG's. After my last speeding ticket back in September, I decided that I'm tired of getting tickets and decided to change the way I drive. So I now have realized that "racing" to the next stop light gets you no where faster than anyone else. So I now gently accelerate from a stop, I stopped the passing everyone on the road (two lane roads). If I can I will coast up to a red light or a stop of any sort. I work nights to so that helps with the traffic factor. I usually don't use the freeway but for maybe 10% of my actual trip. I drive about 15 miles to work with a altitude change of about 1,000 feet. Speeds are usually 45mph up to 60mph, more so at 50mph. Plus now that it has been cool enough not to use my AC, I'm sure that helps too!

So this change has equated to the computer telling me 25-27mpg with an actual calculated MPG's of 22.5-23.8. It's hard to control the urge to romp it too, since that was my normal driving style.