Anyone with a 4.6 out there . . .

[David Harris]

Just wondering what kind of fuel mileage those running 4.6's are getting compared to the original 3.9/4.0 motors? Thinking of Discos/RR's . . .

 

[upcruiser]

I have a 4.6 conversion on the original 3.9 in my D1 5 speed. The truck runs stock gearing and 235/85's. With the RTT up top I manage 12-14 on the road driving modestly. Without the RTT on and just the basket I was getting 14-16mpg under the same conditions. Hope that helps.

 

[Viggen]

Dont forget to mention gearing as that too will play a part.

 

[David Harris]

Dont forget to mention gearing as that too will play a part.

Yeah. Just trying to get an idea whether there is a mileage trade-off between the smaller and larger displacement motors, all else being equal.

 

[R_Lefebvre]

I think it would be a practical impossibility to answer your question with real-world results. Too many variables.

Theoretically... A smaller displacement engine should use less fuel. But if you're working it hard (open loop fueling) the smaller engine could use more fuel than a more relaxed bigger engine.

ie: back in my college days, I went on a climbing trip with a bunch of guys in upper NY state. 2 cars, mine a 2.2L Tempo 5 speed, vs. a 3.0L V6 Taurus auto. Both cars each had 3 people, loaded with climbing and camping gear. The Taurus used less gas on that trip.

 

[craig]

When I swapped the 4.6 into my 4.0l DII I saw an improvement in MPG. That's because the 4.0 was underpowered for the DII and I regularly had the pedal to the floor trying to get it to move. With the 4.6 I always had power in reserve and was able to drive it with much less gusto.

I'm driving a 3.9l RRC with small tires (215/85/16s) and it seems to pull plenty strong. In this case, I can't see a 4.6 improving things.

Craig

 

[spikemd]

I have a 2001 Range Rover with SD roof rack. I get 15mpg combined with a light foot. Without the rack and the older 'highway' tires the previous owner had on the truck, I got up to 19mpg on the freeway. With the roof rack and AT tires, I get around 17 on the freeway.

Its a heavy truck and I would recommend the 4.6 over the 4.0 for my vehicle. It has good power and loads of torque so you don't need to rev it much, but has reserves if you need it. I also have the Bosch engine (from 1999-2002 RR) as opposed to the GEMs which I believe is more efficient.

 

[Dave Legacy]

I had a 2003 D2 4.6L w/ 265/75 BFG MTs, SD Rack w/ Hella 4000s and I would get 16MPG highway, but typically approximately 10MPG city. 250-280mi of mixed conditions to a tank. Oddly better than what my LR3 4.4L is doing on 285/60s.

 

[R_Lefebvre]

My truck currently with the 245/75/16's, 2" lift, front bumper, rear bumper, winch, etc, and the R380, I've gotten a best of 18mpg on a backroads highway trip. Down to 12mpg on a trip towing my big ************* trailer and with a canoe on the roof through the hills.

I'm not sure what it gets in normal usage, because shortly thereafter I started having O2 sensor troubles and was spewing black smoke...

 

[Pedro79]

12-13 in town 15-16 hwy, I have a 2inch lift and 245/75/16 tires. Seems about the same as when it was stock height.
04

 

[David Harris]

All of these figures seem to be what my 96 Disco 4.0 with 31's gets. So, I guess that means no real penalty for upgrading to the 4.6 . . .

 

[Chazz Layne]

Stock (255/55R18): 16-19 MPG

Lifted 3" + roof rack (stock gearing, 265/75R16 on NATO steelies): 14-17 MPG*



* up to 17 MPG highway figuring a cruising speed of 65. 10-12 MPG if I go 75...

 

[AxeAngel]

I cruise at 75-80 on the freeway get 12-14mpg when doing so, around town I drive like a snail and do slightly better.(with little tires)

When on the highway and driving 65 my scanguage reports 18-20mpg(with little tires)

big front bumper, big rear bumper with dual swings, winch, sliders, recovery gear.

I have a 4.6l with less than 10k on it, tcase was swapped out less than 10k ago. Keeping your fluids fresh and reducing all friction from the hubs and diffs is very important.

When running 33s my mpg drops about 3-4mpg.

-Sam

 

[05LR3AZ]

I had a 2003 D2 4.6L w/ 265/75 BFG MTs, SD Rack w/ Hella 4000s and I would get 16MPG highway, but typically approximately 10MPG city. 250-280mi of mixed conditions to a tank. Oddly better than what my LR3 4.4L is doing on 285/60s.

That is interesting. My LR3 puts my D1 to shame... my D1 was getting 14+mpg (on 33's) on a recent road trip. My LR3 got close to 20 with the 285/60's.

I took a trip with some other D1's and D2's and the D2's (4.6L) were getting 2+ mpg compared to the D1's. All the vehicles were comparably equipped - tires 33-35's, stock to 4.11 gearing, all loaded with gear.

 

[pangaea]

On my D1, I believe the mpgs rose from about 9.5 in expedition gear (33s, fully loaded roof rack, bumper, at GVW) to about 11 or so when I went from a 3.9 to the 4.6.

I think the fuel economy increase was largely because the smaller engine had to work so much harder, especially going over the mountain passes here in Colorado.