So I was cruising on the freeway at around 80 MPH in my 2008 TL type S and I wondered "hmm, I wonder how many miles per gallon i'm getting at this speed..."

I check my display under the speedometer and reset the "Trip Commuter" option so all the average "MPH", "MPH", "Distance" and "Time Traveled" options are fresh, and to my surprise the display reads:

AVG MPG: 39
AVG MPH: 78
DISTANCE: 7
TIME: 0:06

When I finally got off the freeway I checked again and the display read:

AVG MPG: 36
AVG MPH: 69
DISTANCE: 24
TIME: 0:21

I'm a bit skeptical about the information on the display. It seems a bit odd to me that a 3.5L V6 could achieve such fuel efficiency, even at highway cruising.

What I want to know is:
Are other TL type S owners getting the same results? Do you guys think my sensors are just out of whack?

Some things to note about my car:
-'08 TL-s
-6 speed MT
-lowered on H&R Sport Springs (~1.4 in drop)
-Mid Muffler delete
-Swapped DYNOMAX resonator
-Odometer reads 22,000 miles
-never changed air filter
-oil life reads 30% on display
-Tire Pressure is 39-Front 37-Rear when running/ 36-Front 33-Rear when cold
-Driving on flat cement freeway
-Cruising on 6th gear majority of the time, occasionally on 5th. Never rolled on neutral during the drive.
-outside temperature: 60 degrees F

If this is normal, then i'd be very glad! I know Honda's get great gas mileage... but this is a little fishy.

 

I have seen mid 30's at prolonged highway speeds. But I drive in a hilly suburban area 90% of the time, so I average around 20.

 

i average around 20ish too. best i've seen was on my way back home to buffalo from georgia where i bought the car. averaged around 24-25 IIRC. i'm still happy with that mileage though, as my 2000 blazer routinely gets around 10mpg.

 

Oh i'm sorry, I think my post is a bit confusing.

The averages i'm gettin up on my first post are referring to purely sustained hwy driving, not combined city/hwy MPG. My display usually says I get about 23MPG average. Thanks for the input!

 

It's accurate.

This just goes to illustrate how detrimental everything else is other than constant cruising.

I have done this same experiment too on numerous occasions. Get up to freeway speed, set the cruise control, then reset the MID. Watch the super high mpg while on the freeway. Exit off the freeway, and watch it crater. For fun, check your mpg before turning off the engine. Next morning, check your mpg after approx 5-10 minutes to warm-up the engine. Super crater.

Cold start-up, stop-n-go traffic, red lights will DESTROY gas mileage. Absent of these damning elements, one will be surprise at the fuel efficient of their automobile.

 

Yep it sounds about right. On most highway only trips I average around 29-32+mpg, as soon as you throw in the city driving though it drops pretty quickly. On a tank where I've spent about 75% highway / 25% city I'll typically hit around 27mpg.

 

Who knows, everytime I'm on a road trip I end up seeing a patch of road I want to drive quickly through and end up ruining my MPGs.

 

yup its about right i've gotten 38mpg with a 5AT on highway, not as efficient in the city though but who cares the car is awesome!

 

Thanks for the input guys! It's good to know that all is well with my MID.

I try to keep my MID off the Trip Commuter setting to make my life easier now. It stresses me out watching my MPG go down when I hit red lights!

 

My MID always reads 2-3 mph less than what the speedo shows. The mpg has been pretty accurate at about 32 mpg, but certainly not 38mpg. You might want to take a test of your own by measuring miles driven vs. gallons consumed. Do this a few times to assure accuracy. Overall winter driving at 80% freeway has been 29mpg, 32 in the summer.

'07 TL-S A/T CBP
FUJITA F5 CAI
PROGRESS RSB
BRAILLE BATTERY
P2R THROTTLE BODY SPACER
V1 ON THE LOOKOUT

 

It's not too high. You're overall fuel mileage will even out when you refuel.