I checked again last night on a very flat straight stretch of highway using cruise control. At 70mph, the mpg is right at 30. If I bump up the speed above 70, mpg goes down. At 80, it is right at 25mpg.
This is monitoring the instant mpg in the trip computer.

 

Highest I've ever gotten was like 28.8 mpg going from VA to NYC.
I basically would keep it steady at around 70-72 the entire way.

 

it is true an rl is good on hwy. I just go 30mpg going 85-90mph on I-95 from Miami Fl to VA and did great going down got 28MPG going 80mph from va to Miami FL i dont know what that was though. unless va gas sucks. lol.

 

If I drive very conservatively at 68 mph for 90% of a tank and carefully for the other 10% then I might get 24 but typically 23. California is up to 10% Ethanol, summer formulation and hot so my gas is expanded. I have never had more than 26 mpg in the 142000 miles of driving it. I would need to drop it from a plane to get what some people are posting.

 

Same here. I cannot see how anyone can get 30mpg above 80mph. Not happening in my car.

 

Not here either. I would also like to know if this is the computer average or the actual numbers average. One thing I have thought of recently is that a meter is rarely perfectly linear and is calibrated for the optimal rate. For instance a speedometer can be highly inaccurate below 10 mph and above 110 mph. The flow meter on a gas station pump runs at the same flow all the time whereas the flow meter on your fuel pump has to cover idle to WOT flow rates. I have a feeling that the accuracy at idle is very poor. If I have a high MPG average but then sit in a parking lot, I find that my actual MPG is much lower than the computer average.

As for db and getakey's comments, I have seen a 27 mpg average on the computer with 100% highway driving @ 65 mph a couple times and that is not with a tail wind or a consistent elevation descent. I believe that with a good tail wind, 28-30 is completely possible. I have read that the Autobahn does not have more than a 4 degree grade at any point because the affect of such an incline on MPG, especially at high speeds, is very significant. In the same sense, a descent from CO to Houston should yield a pretty good MPG. It helps that the wind is usually blowing from the NW there too.

thephantom, it is possible that the hot temperatures are raising your tires' pressure to a more optimal PSI.

 

^ that's similar to my experience.
I have been on 1/2 dozen or so long trips (400+ mils) with virtually 100% Interstate driving. I would typically average 70mph and my ave mpg was around 26

 

I may understand its impossible and i thought so, but taking a trip down to Miami, only using Bp premium gas, and before the trip getting oil change fluids flushed and BG service, i got 27-28mpg all hwy and using cruise control at 75-80mph but coming up was a whole different game. i will say i got 27mpg again but my computer was reading 30mpg all the way home. and that was for trip a trip b was reading 29mpg and i used cruise control at 80 sometimes 85 so i dont know maybe something wrong with my computer but i was shocked. but i can understand with this car avg is 25-27mpg straight hwy. but now that i've been home and its aweek that ive been back im getting 20-21 city mpg and 26-28hwy..


Question on avg how many times are you guys filling up? and honest what grade are you using? also how many miles do you guys get on a tank? (including city drive and hwy)

 

I was reporting numbers shown by trip computer which others have reported may be somewhat off (typically high?)

The trips I made were 400 to 600 miles. Filled up once or twice during the trip. I do not have my trip computer to reset upon fill up so the ave mpg were for the whole trip.

My normal commute is about 1/2 hwy 1/2 city. Typically ave 18 to 19 mpg

Interesting on the Range is that upon fillup, it will usually show 400+ range. However, somewhere between 40 and 80 miles left on the range, it will drop 20 miles off the range. For example, I'll be driving and it will show 60 mi range and then suddenly drop to 40 mi range. When the low fuel warning comes on, it is around 20 mi range. However, if I fill up right at the low fuel warning, I can only put in 16.5 gallons.

 

It's already been stated that some gas has ethanol which will rob your MPGs. TX has up to 10%. OK doesn't have any. I use 93 octane as TX doesn't supply 91, but we have the ethanol.

The most distance I have seen on a pure highway trip was on the range of 370 miles, but that was because I didn't have a gas station down the road to keep driving to. I usually fill up between 15.5-16.5 gallons and that is usually between 300-330 miles.

The range calculator has always puzzled me. I have seen it read 495 miles. With our 19.1 gal tank, that would be 26 miles/gal and a fried fuel pump. I don't understand why they even put stupid numbers like that into the algorithms, especially since the range will read 0 after 17 gallons.

Keep in mind that a smaller tire/wheel diameter will inflate your readings erroneously. However, you probably have to be riding cholo style to see a noticeable difference.

 

I got 29.8mpg via the car's computer driving 47 miles on the freeway this past weekend doing an average of 75mph. Pleasantly surprised. Drove with VSA off, don't know if that had anything to do with it. Pretty sure I could have hit at least 30mpg if I kept going on the freeway.

 

what made you turn the vsa off?

 

Meh, just wanted to drive without it because the other cars I used to drive didn't have the luxury of having VSA, and were RWD. Didn't want to get too dependent on VSA. Didn't see the harm of turning it off, and honestly, it doesn't feel any different on dry pavement.

 

right on

 

here are pics when i went to fl about july and then recently 10/9/2012 when i went to go drop my NHB RL to its new owner's house. made 30-32mpg hwy. and drove a little city getting to his place. and i didnt reset anything you will see that in the pics.

miami first driving down there, then coming up after putting premium BP only.





and 10/9/2012 driving hwy and city to NEW owner's house

 

wow that was impressive, during the summer i drove my rl from la to las vegas, and i got around 30 mpg which i think it was pretty good