I drove from Panama City, FL to Fayetteville, NC today - I spent the whole day drafting behind semi trucks (hardly any wind resistance), at about 70mph. My average MPG jumped to 36.8mpg when I calculated the numbers (622 miles - 16.9 gallons of fuel)

When I usually drive this route, I go about 80 mph and never draft and I get about 28mpg! More proof that because the EPA doesn't do testing in any real world environment, with no simulated wind resistance, numbers can easily be inflated. I blame this as the primary reason why so many owners can't achieve the EPA numbers!

 

I used to get that before 18's......

 

Thats a pretty big difference......I'm going to have to try that!

 

my worry is rockchips - ive got enough...

 

I am not willing to save a few dollars in gas at the expense of a new windshield.

Besides, I have hit 37 MPG in my auto on a few roadtrips.

 

yeah i'm cool off a billion rock chips.

 

driving at 70.. if you're an auto.. your tipping the 3k RPMS.... I've noticed that on the highway if you go above 3k rpms.. you totally KILL your gas mileage.... I drove like 80-85 from Miami to Atlanta.. and got like 26-28 mpgs (trying to remember).... but on the way home... i never went above 75 and drove around the 70 range and my mpg's was in the mid 30's... (just no rush to get home)

The key is not to go above 3k rpms at ANY time while driving the box if you want to save fuel.

 

I think it's a combination of two things that have been mentioned here. First is the wind resistance. Let's face it, the xB is about as aerodynamic as a self-storage unit. Anytime you eliminate that much drag, it's going to make a difference.
The other issue is the gearing and engine revs on these little motors. There will be a dramatic difference in gas milage from 70 mph to 80 mph. It'd be like driving 35 down a street in 2nd gear all the time.

 

How fast is that 3,000 rpm in 5th gear (manual)?

 

I wouldn't worry so much about the windshield as I would the paint. There's a lot of sand and smaller pebbles that those trucks kick up that you don't hear but they are sandblasting the paint on the front of your car. My front end is very rough looking because of it.

 

^Exactly. I never follow too close to tractor-trailers. It's not worth the damage.

 

3250rpm @ 65 MPH.

 

[quote="vintage42"]
that may be a good rule of thumb, but I don't know that I'd bet the farm. My last tank disproved the 3kRpm 'rule'.

rock chips or not, it was a good experiment, and good info. (read: thanks for trying it so i didn't have to!) Its obvious that the xA get better mpg due to it's design. Kinda makes me think that a properly designed front fascia (bumper/lip/whatever) could really improve the economy of the box.

 

can't speak for an xB, but our xA got over 40mpg on a long trip and RPM averaged 4k for nearly the entire trip. We average 38mpg with a combination of city and highway driving, and most highway is done at 70 to 80mph.

 

Yeah the rock chips are totally not worth it. I wouldnt draft a semi if it got me 50MPG. Just not gonna happen with me. I cringe everytime I get on the highway because I know my paint is getting hammered....

 

That's not too shabby considering you're driving uphill the whole trip!

 

With the xB, I'd say the best speed to get good mileage is 65-70mph (manual). I went about 800 miles doing 65-80mph and peaked at 41mpg (average was 35mpg). I only had about 375lbs of total cargo/passenger weight too (that helps), but no drafting. I did notice a huge difference in MPG once you do ~80mph.

 

I get about 28mpg doing 80mph and about 34mpg if i keep it under 70mph which takes an enormous amout of restraint. I have got so many chips and scratches in my front bumper i gave up on trying to avoid it any more. The only thing i won't ride behind is a flatbed especially if it has a dirty piece of construction equipment on it, you know where you can actually see the large pieces of gravel rolling toward the edge with each bump it hits. That should be illegal (it could seriously injure a motorcyclist)

 

My 5-spd 05 "toaster" has essentially stock running gear (205/55x15" for a .6% variation --- indicated 60mph is actually 60.3mph) and on the highway works out this way:

60mph = exactly 3000rpm
65mph = 3500rpm
70mph = 4000rpm

My best MPG figures to date (20,000 miles) were on trip from Columbus, OH to Naperville, IL: steady 65mph over 120+ miles = 35.4 MPG/highway.

By comparison, weekly averages (mostly beltway driving @80mph with balance heavy traffic city) work out to 29-30MPG/mixed (summer or winter, doesn't seem to matter much).

BTW, my xB does have AEM cold-air and axle-back TRD sport exhaust --- not sure if that's helping or hurting the MPG (probably negligible either way?)

Hope this helps someone . . .

 

ummmmm

60 is 3000
65 is 3250
70 is 3500
80 is 4000

your needles must be off. well sort of. that or a constantly slipping clutch.