Hey all,

Got 6k miles on the OR and so far so good. I was wondering, what is the optimum cruising speed for the X. It's a big truck and was wondering how hard should we push it to get to a point where it is getting the best mileage and power. Hope this makes sense???

55-65 is really optimal, perhaps 55-60 being the best, but if you do a tick over 70 mpg and you won't see much over 18.5 highway.

no different than most trucks...some cars may be able to get better numbers at 70-75 due to wind resistance and rolling resistance reductions compared to bigger vehicles. 55 mph was mandated back in the 70's to save gas. air resistance is an exponential thing...something like the force to maintain 150 mph is 8 times more than what it is to maintain 75 even though velocity only increased 100 percent. wind at 50 mph is practically nothing so 55 does save fuel.

Thanks for the answer...does it hurt the X by just leaving it at 55-60mph all it's life?

Well, you will have to stop to refuel unless you can find someone to refuel you while driving.

Sleep can be an issue too, but I know some people who switch drivers while driving, so you may catch some sleep while someone else is driving.

Food and personal hygiene could be an issue too.

Joking aside, I can't see why it would be a problem. You still stop and accelerate so you get to work all the gears. Most people I know drive the same speed all the time, typically 10 over the posted speed, only slow down for traffic and only go over to pass others on a two lane highway.

I've never heard of anybody having problems because they always drive the same speed. I also never heard of anybody driving different speeds to avoid damage.

The reason I ask is the engines in the cars in Japan, get swapped out every few years before of mainly city driving so the engine doesn't get to open up and breath on the freeways like ours, piston and rings problems too. So would damage be done to a sports car engine if it was only used for city driving or limited to a certain speed? Our should a couple high speed runs be needed to keep the engine good.

The engines from Japan that I have swapped were wonderfully new and nothing wrong with them. The engine swap thing, as far as I can figure, is a way to support the (japanese) domestic car industry by punishing the ownership of older cars and at the same time satisfying people in gov't that the new cars making up the bulk of the fleet help with smog since they are cleaner than well worn cars. Of course the cars they consider old really aren't by anybody else's standard.

It seems to be part of Japanese culture to always have the newest, smallest, 'bestest' thing.

I recently travelled from San Francisco to Los Angeles and all along I-5, for the most part I was doing 75-80 with very minimal lane changes and I was able to get 20 mpg. My truck had about 10k on it at the time. I was on cruise control also.

Set your cruise-control to equal the speed limit. Works good every time.

For what it is worth - I drive a lot of 70-80 mph on the highway. I usually keep my rpms(manual tranny) around 2200.

My mpg is consistently 21-22 mpg. FYI - I do the manual calculation of gallons poured in by miles driven.

I typically drive around 75 MPH and have seen my MPG at 21 as on the sticker. If it is really windy that is another subject, as it drops to about 18-19 MPG, but that is to be expected.

If I maintain 18.5mph I will get 70mpg? nice!

I have checked my mileage at 75 mph-17.9 and at 65 moh-19.9. I will check my mileage at 60 when the weather turns nice again and see if there is a difference. Of course that will be next spring sometime.

I had to haul a ton of krap to a flea market this past spring (just stuff inside, no trailer)...it was 4:30am - I was tired so I just set the cruise to 50 mph and drove like 45 miles total..got 23-25+ mpg (which I havent seen ever again since I normally drive like 85 mph

so I'd say 55 and under is best mpg as most cars....60 and over and your dipping in a few mpg's

Now have well over 18,000 miles too! Good break in I guess....

Over the holiday I drove 1,700 miles. Hit a few major traffic snarls and some of it was through the mountains, but mostly kept the cruise at 70-73. Got 23 mpg.

You have to remember you can't compare a 4x2's gas mileage to a 4x4. They are totally different trucks when it comes to drivetrain and gas mileage.

I posted something in the other thread about manual shifting speeds. It seems to me that the issue is not at which speed the truck should be run at, but at what RPM your at whatever speed your going. For instance, driving 70 MPH at 4200 RPM's (what's that, 4th gear?) may mean that you can go equally fast up a 32% grade as you can across flat open farm land - because your torque curve is at its peak, all 280 foot pounds of it - and the resistance probably never exceeds that number (well maybe at 32%..). However that is total overkill and you'd be burning fuel just to keep the pistons pumping.

The same applies when you're at 900 RPM's in 6th gear going 30 MPH and your engine knocks every time you go drop below 28 and have to accelerate back to 30..

It would be cool if there was a resist-o-meter gauge in the Xterra gauge cluster. Basically it would work like a torque converter in an automatic, only it would be graphical and tell you when your resistance exceeded a certain torque limit where it cost more fuel at X gear than it was worth, or where the resistance was so far below the torque number that you were wasting RPM's.. Like two numbers, say - 220 resist, 214 torque - means you need to shift down.

I remember reading on the 2006 Xterra brochure of Canada that you can find 90% of is torque at 1900RPM. I guess that would be the ideal speed for the engine needs, that would probably be the lease amount of fuel needed to turn efficiently.

Sounds about right to me.. Anything past that falls into the realm of diminishing returns for the fuel it costs verses the few extra foot pounds of torque you gain.

I'm back to my old driving habbits again and I do tend to shift at around this RPM, and run just under that in the 1400 range (probably closer to 60 - 70% of peak torque - but acceptable with lower resistance).

As a lot of others have pointed out, it does really come down to feel, and it is very much like riding a 10-speed bike. I think the 4.0 L in the 2nd Gen is more than robust enough to handle the lower end and is a prefect fit given the size and weight of this truck.

I agree that the 4X2 and 4X4 are little different but here is what I have found. While driving to Seattle last weekend I found that above 65mph (70-75)my gas mileage was around 17-19 mpg but if I kept my speed around 55-60mph I tended to average 21-23 mpg. On a separate topic I was surprised at how nice the X tracked on the freeway at higher speeds--felt very well planted. It also has a lot of torque no matter what speed you are going!

just curious if there was a way to get the mpg option installed on a OR...I always wondered why they didnt include that on the OR.

Because OR models owner (typically with 4x4) would be more depressed.

I average 15 MPG on communting, and my last highway trip was a whopping 16 MPG (With winter gas and a lead foot)

hahah very true...... im in a state of denial! so how's that cheerleader thing going down in Mckinney?

jandrew, I was also pleasantly surprised. I did 800 miles of highway over the holiday. Kept it at 70-75 mph, occasionally popped up to 80 for short spurts. All 6th gear with rpm's steady at 2000-2200. And it tracked like a laser, very solid. I also had continuous power at all speeds the whole trip. Of course, my mpg experience was a wee bit different than your SE, but I'm not complaining.