After reading numerous posts about how inaccurate the trip computer is in calculating MPG I've decided to use some of the statistics tools I've learned to try and figure out:

a) What MPG we can expect for different driving styles/environments?
b) How far off our trip computer is in calculating MPG in different situations?

Here's what I'd love to get from as many folks as possible:

Indicated MPG -
Actual calculated MPG -
Average Speed from trip computer -
Octane -
% of city driving for tank -
% of highway driving for tank -
Driving style for tankful -
Estimate of % of time on cruise control (with set speed) -
Transmission type -
If 6 Speed, what was cruise gear -

To do this the best, I'd suggest you drive the same way (whichever that is) for a tankful of gas (after reseting all the trip computer values at the start), and then submit the data. Once I get enough data I'll do the analysis and post results.

 

Indicated MPG - 37.2
Actual calculated MPG - 31.15
Average Speed from trip computer - 54 mph
Octane - 93
% of city driving for tank - 5%
% of highway driving for tank - 95%
Driving style for tankful - Grandmotherly (I was trying to see max mpg, *WOW* was it boring. I felt like a rolling roadblock on my 75 mi/day highway commute)
Estimate of % of time on cruise control (with set speed) - 95% (exactly 65mph)
Transmission type - MT
If 6 Speed, what was cruise gear - 6th

 

If you're getting 31.5 MPG, it's being towed on a flatbed with the motor off. The trip/MPG computer is junk. I've gotten 44MPG according to the computer which is why I don't use it other than if I want a good laugh. In reality, I've never gotten more than 25MPG on a 150 mile highway trip. Lowest for me 17.5 mostly local/city driving. My last few averages have been 20-21 mixed city/highway. I get on it a little with the occaisional mustang or riced out civic, but most of the time the car isn't revved over 3000-3500RPM.

 

Oh yeah, I only use 93 octane-there is no 91 in the Philly region. Also my mileage dropped about 2MPG during the dead of winter probably because of a longer warm-up and because the gas is 'oxegenated' or whatever it is they add to it during winter months for pollution reasons(I think). Oh, and if you couldn't tell by screen-name, I have a 6sp.

 

I guess you didn't read the whole post. The trip computer said I got 37.2 which is obviously wrong. The actual milage I went was 286.6 miles on 9.203 gallons of gas, which does work out to 31.15 mpg. As stated in the post, I drove like a total candya$$ for that distance just to see how high of an mpg I could get. It was absolutely NO FUN at all, and I never intend to try it again.

That said, I'd like to get as many datapoints as I can to figure out just how bad the computer is, and what ranges of driving styles/conditions produce what results.

 

Indicated MPG - 25.4
Actual calculated MPG - 22.1
Average Speed from trip computer -
Octane - 93
% of city driving for tank - 15
% of highway driving for tank - 85
Driving style for tankful - semi aggressive
Estimate of % of time on cruise control (with set speed) - none
Transmission type - auto

I usually figure out my mileage each time I fill up. The trip puter is always around 3 MPG higher than actual.

 

Thread # 349583897 about the trip computer being about 4mpg off?

 

Can't seem to make it come up. Link?

 

I'd really like to see a bunch of data so we can determine if the error is an absolute value (always 4 mpg off no matter what your observed mpg is), or if it's some stable (or changing?) percentage of the observed. Given the reading I just took is off by over 7 mpg, I'm guessing the "4 mpg" isn't necessarily always true. There's also the possiblilty that the difference won't be the same over different driving styles. I'm willing to run the numbers on it if folks will provide data.

 

Actually I did read the whole post and I was completely clear that you calculated that mileage yourself. My next comment about the trip computer might have made you think otherwise, but only the computer can come up with a rediculous number like 37.2 or 44(in my case). My car will never see 31. I'll never have the kind of discipline you have.

 

Trust me, the discipline lasted a total of 286.6 miles and was painful to do. I got real tired of Grandma's going by me in their Ford Festiva's and Toyota Matix's. At 65 mph on I-70 between Columbus OH and Dayton OH (Truck central) you're almost a danger to the highway system. I won't be trying it again. But, I had to know what the high end of the range was. Maybe I'm a masochist?

 

Only if you continue with that behavior.

 

Indicated MPG - N/A
Actual calculated MPG - 21.9
Average Speed from trip computer - N/A
Octane - 92
% of city driving for tank(s) - >90%
% of highway driving for tank - <10%
Driving style for tankful - normal
Estimate of % of time on cruise control (with set speed) - NA
Transmission type - automatic
If 6 Speed, what was cruise gear

Your data will be much more accurate if you compare the data over several tankfuls. Data I am providing is over 8000 miles (record distance / gas used at every fill up). Monitoring over time is a good indication of engine health (or change in driving habits!).

 

I checked mine very closely for 3 consecutive fillups. and found on premium with mostly under 50mph driving, no cruise; computer said about
22-23 mpg but i was really getting 19-20 mpg.

 

i will post exact puter readings later in week just filled up and reset everything before work this afternoon.i always check the puter to actual and am usually at 23 to 23.5 on puter and 19.5 to 20.2 on actual. 90 % highway (usual speed 80 to 110).aggressive driving habits unless drinking(speed limit after drinking usually brings puter ave. up 1 to 2 mpg) cruise not used often enough to change mpg

 

Oh great, you drink and drive (and admit it on an open forum)

 

I think the whole odometer is off. From my work home my trip meter says 19.9 miles but my other two cars say 21 miles. All tires are original size.

 

Indicated MPG - 20.2
Actual calculated MPG - 16.9
Average Speed from trip computer -
Octane - 93
% of city driving for tank - 50
% of highway driving for tank - 50 (stop and go)
Driving style for tankful - hard driving, abrupt launches, often wot.
Estimate of % of time on cruise control (with set speed) - 0
Transmission type - 4AT
If 6 Speed, what was cruise gear -

The DTE is also laughable. When it indicates 20miles til empty, I still have ~3 gallons of fuel. That's obviously a safety measure, which is nice, but yeah don't trust the computer.

 

I tried that same experiment a while back. I got like 22mpg indicated (so maybe 19mpg actual) and got about 300 miles on a 16.0 fill-up. But yeah, I felt like I was tied up. I was dying as people just pulled past me. That experiment lasted for only one fill-up...

 

i didnt say i was wasted just that i had drank.

 

Indicated MPG - 20.3
Actual calculated MPG - 17.2
Average Speed from trip computer - 23
Octane - 91
% of city driving for tank - 95
% of highway driving for tank - 5
Driving style for tankful - slightly more aggressive than average
Estimate of % of time on cruise control (with set speed) - 0
Transmission type - Auto
If 6 Speed, what was cruise gear - N/A

 

Apparently I'm sick. I did it again, I did another tankful driving like a puss, but setting the cruise at 68 instead of 65 (71 next). Here's what I got:

Indicated MPG - 35.7
Actual calculated MPG - 30.28
Average Speed from trip computer - 54 MPH
Octane - 93
% of city driving for tank - 5
% of highway driving for tank - 95 (cruise at exactly 68 MPH)
Driving style for tankful - Total wimp
Estimate of % of time on cruise control (with set speed) - 95% (68 MPH)
Transmission type - 6MT
If 6 Speed, what was cruise gear - 6th

I got 443.4 miles on the tank, and only used 14.64 gallons, I still had almost 100 miles left on the DTE.

 

Well, it looks as though I'm on par with a few others here:

Average is 21.9, mostly city driving and I only know 2 speeds=fast and faster<my driving style

21.8 is the lowest I've been and all on 93 Octane but then again I do have a very heavy leadfoot.

I think I average about 55mph in the city, which is faster than the posted speed limits and that is only my average, every now and then I push her up to 80 in the city.

Yeah, I know, be safe, slow down idiot, yeah, yeah whatever.

I wish I knew how you guys were getting 30something plus mpg, you must drive like Ms. Daisy.

 

*26mpg avg mixed driving town and highway.

Note: *this figure comes from the old fashioned method of miles divided by Gallons used, not the trip computer which seems to be overly optomistic.

 

If I drove like Miss Daisy I'd probably be getting lower mileage. I was driving more like Miss Daisy's overly-cautious senile older sister with a weak right foot.

It's no fun, but then I've got a 150 mile/day commute. I do all but about 10 miles of it on cruise control, so it gives me a chance to experiment with different cruise setting. The hardest part is babying the throttle on the on-ramps and shifting by 2300 RPM and skipping gears (1->2->4->6). Not recommended for daily driving, just an experiment.

 

Highest ever indicated was about 34. That was at 55-60 mph steady in 6th gear. Typically I get 26-28 indicated which is about 23-25 real mpg when done manually. I drive moderatley aggressive with an average of 80 mph and a few bursts over 100 every day passing people on a 6 lane hwy.

Also-I usually use 90 octane with an ocassional splurge to 93.

 

i normally drive under 3k rpm's every day, just because i am in fear that i may crack up my car, or break something on my car. it is kind of hard to do, just because i am 20yrs old, and i have always had a heavy foot... but this car cost me a lot of money, so i want to keep it in the perfect condition it is presently in. Also, the good gas milage is always a plus. i do about 97 percent city (a lot of stop and go) and 3 percent hwy. on the hwy, i cruise at about 70mph. (5 over limit.) i get anywhere between 290-320 miles out of a tank, and my trip usally says i get between 21-23 mpg. as calculated just now, i am technicly getting between 17.8-20mpg.

intresting stuff. i will do more calculations later, and give you an update.

-Chris

 

Indicated MPG - 28
Actual calculated MPG - 21
Average Speed from trip computer - 35
Octane - 91
% of city driving for tank - 95
% of highway driving for tank - 5
Driving style for tankful - Speed limit maybe a little over (5-10) no hard accelerations (that I can remeber )
Estimate of % of time on cruise control (with set speed) - 0
Transmission type - Auto

 

my most recent tank, weekend roadtrip, 95% highway, I babied it, accelerated very gently and sat on the speed limit.....
Actual: 25.6 mpg. Indicated: 28.4 mpg.

 

Yup, I've noticed that the actual mileage for me is about 3-4 mpg less than the indicated mpg.

 

Indicated MPG - 22.1
Actual calculated MPG - 17.7
Average Speed from trip computer - 32 mph
Octane - 93
% of city driving for tank - 75%
% of highway driving for tank -25%
Driving style for tankful - 100+mph on hwy for 10-15 mins of commute. ~30-40mph for 40 mins of commute
Estimate of % of time on cruise control (with set speed) - 0%
Transmission type - AT

 

i get 15 mpg mixed

 

Indicated MPG - 33.4
Actual calculated MPG - 28.6
Average Speed from trip computer - 53 mph
Octane - 93
% of city driving for tank - 90%
% of highway driving for tank -10%
Driving style for tankful - Mellow
Estimate of % of time on cruise control (with set speed) - 85% (71mph)
Transmission type - MT

 

12.36 mpg, all city, nuff said