[Bails]

Best High speed consumption I've had is 10.3 Ltre/100 klms when driving around Australia. Got this cruising at 160 kph on dead flat Northern Territory Highway with cruise control on. My average for everyday driving is about 14.5 klms/100 Klms.

 

[courtfetter]

I think you actually have it backwards. When your speedo reads 70mph your likely only going 65mph. This is the norm with all manufactures. This is with new stock sized tires of course. This therfore directly translates into your miles travelled which will obviuosly affect your manual and digital/automatic calculations. A 5% inaccuracy will give you 2-3 mpg worse than your computer is telling you.

 

[courtfetter]

Bails, that's closer to the norm, 22-23mpg on your highway trip with 16-17 on normal day to day. Day to day seems a little low. I tend to have a heavier foot around town giving me 18-19mpg. This heavy foot does not affect anything while on the highway with the cruise control on though.

 

[EARL97850]

On VW models, the odometer is calibrated correctly. The speedometer is the one that is calibrated slow.

Cya

 

[courtfetter]

Has anyone heard of a product that allows you to adjust the turbo boost on the fly? Several Amercian companies have them for your typical American Diesels (Dodges, Chevs, and Fords). These are great as it allows you to set your engine on efficiency when just commuting, giving 10mpg gains and then allows you to hit a button to race up a hill, when towing, etc. Anyone heard anything?

 

[courtfetter]

Sorry Earl but the speedo and odometer are directly corelated. Just try puttin 31" tires on, which will make you speedo bang on. Big dif. The stock tires are only 29". Smaller size will always give you high mpg and overall speed.

 

[EARL97850]

Better check VW history...They can be separately calibrated for different things.

Cya

 

[courtfetter]

Two reason why manufactures likely play the small tire game:
1. Liability potential with traffic accidents, speeding tickets, etc.
2. Your warranty wears out faster. 50,000 miles is only 47,500 miles and that's not factoring in a worn tire will read even higher speeds and longer distances than a brand new tire. True number is closer to 46,000 miles.

 

[courtfetter]

How else would my 60 mile commute to work change to a 56 mile commute when I got larger tires?

These tires corrected my speedo. I never changed anything else?

I'm sure that each item can be digitally corrected individually but it's pretty basic. Distance travelled (odometer) and distance travelled divided by time (speedometer). There's not 2 separate meters (speed & distance) Only one for distance travelled and everything derives off of that.

What I'm trying to tell you is you need to accurately measure your speed (with a GPS) and your distance traveled (test sections). The factory settings are not correct.

 

[EARL97850]

Agreed that the factory is not correct.

You can have (test sections) that match your odometer and also have a speedometer that registers slow or fast at any wheel diameter.

If the odometer is correct at a given wheel diameter it does not matter how fast you say you mpg figures are at.

The only thing that changes that calibration is a change in one of the factors. (diameter..ie..worn tires) It won't change that much.

My Jetta is always 2mph slow at any speed on worn tires and 3mph on new tires and my odometer is dead on the money. (Except for this minor change.) This is checked by test sections, GPS and over 60k miles. The worn tires at the end of their lifespan does not change things that much.

I'm no math expert but any mileage claims made are not going to change that much. You stated that you changed your tires to a larger size, and by doing so you changed your speedometer and odometer. Both of those meters changed in the same percentage that they were calibrated before your tire change.

Cya

 

[courtfetter]

I agree, by going to a larger tire, I changed the distance travelled. An old tire (smaller) will always give you a high mph than a new tire because a new tire has a larger circumference. This larger circumference gives you a longer distance travelled everytime the tire turns 360 degrees. This will throw your odometer and speedo off. You may not think it's much but it is 1-2%

What size of tires are you running? If they are 255/55 R18 then I would estimate that your claimed 28mpg is actually 25mpg. That was my original size and when I got the size correction, I saw my mileage drop from 24 to 21, based on my driver characteristics of course.

 

[EARL97850]

I'm running 275/45ZR19's. I haven't made any mileage claims since I only have a V6. My speedometer is off by 3mph at slower speeds and 4mph off at hwy speeds. Shortly I'll be getting new tread, and I suspect it will decrease my speedometer error by 2-3mph vs. the 3-4mph I have now.

Cya