The automatic loses efficiency due to the torque converter. That bleeds off some of the energy, thus causing a slight loss.

 

I've got an automatic and I average about 29 mpg combined highway/city driving.

 

I'll never see those high mpg numbers, can't keep my foot out of it, street or highway, very seldom under 4500rpm, away from a traffic light always 6500 thru 3rd gear and depending on the posted speed maybe thru 4th gear. Highway 80+ most of the time. I generally get 30 - 32 mpg, but I do have fun!

 

i hit 33.1 in my 06 MCS!

 

I get 99.9 all the time. Too bad it won't stay there all the time.

 

I wonder if some of the people with the high 40's mpg have the settings wrong in the OBC?

If you are set to UK Lang, then you will get IMP gallons = 5 quarts/gal. and your readings will be high.

The US Lang setting give you US gal = 4 qt /gal.

It's odd that the IMP vs US mode is done via the language select menu.
I would have thought that the selections would have been in the other menu where you change from mpg to kpg etc. If should have been mpg-IMP(UK) and mpg-US or some such and not in the language menu.
.

 

I have a 2004 MC manual transmission and I've always been a very close watcher of my MPG since the day I bought my MC new. I've plotted my MPG in a spreadsheet from the very first day I bought the car. If I were to boil this info down to absolute numbers that you could compare....on an average my calculated MPG used to run around 36.5 MPG plus or minus 1 MPG. Somewhere around Sept 2009 I modified my MC with K&N CAI, CAT Back exhaust, GIAC ECU tune and a MSD ignition coil and wires. At that point the MPG went up to around 37.5 MPG plus or minus 1 MPG. From that point in time until just yesterday my MPG has been slowly dropping off until the average MPG was about 35 MPG. Throughout all of this time most of my purchases have been SUN 93 Octane. Yesterday I ran 5 ounces of Seafoam though my intake manifold and beside the reduction in the mosquito population in my immediate area the MPG appears to have taken a very noticeable jump back to the higher numbers. I'm not one who likes to base my opinions on instantaneous measurements, so it's really hard to say at this point in time (one day) just how much my MPG has gone up, but after I have had a chance to accumulate some average numbers I will post back here with the data after the Seafoam cleaning. I might add that on various occasions I have seen calculated MPG numbers that were up above 40 MPG, but in all honesty these numbers were not reproducable from tank to tank and were just glitches in the average. I plan on running a few more Seafoam cleanings on my intake manifold this weekend and will start watching my MPG more closely after I have run these final cleanings and have accumulated some additional statistics on the MPG.

 

Mileage number for me can depend a huge amount on where you live/drive.

I had a car years ago I would track mileage with and when I moved from NY to FL My MPG went up 10% at least. Figuring it was incorrect I duplicated it time and time again.

My explaination is the area in FL I lived in was totally flat. The biggest hill was the bridge over I95 (Palm Beach Area). Coming from all the hills and dales were I lived in NY, to total flatness was a big difference for me.

Maybe this is why mileage seems out of wack to some.

 

 

Fuel cost is a minor cost of car ownership. Tires, oil, insurance, license, etc add up to much more!

 

I own a 64 Cadillac with a 429, 77 Mercury Colony park with a 460, a dodge ram with 5.7 and a pontoon boat with a 115 evinrude two stroke.... mileage? Ha! they all drink fuel for fun. My clubby is ten times better no matter what the mileage 😎