Where are you driving to be climbing a 35 degree grade that is a mile and a half long? Are you sure it is that steep? Is this a public road?

 

Not being sarcastic by any means but i can use some help in math! ur uncertainties are good!

 

Actually I'm being conservative and general in my previous post. I live in the hills and pass over one very steep long grade (35 degrees for 1 mile), hit the crest, then down the other side at about 25 degrees for 3/4 of a mile, flatten out for a short time, and then back up another hill that starts off at about 20 degrees and steadily increases from there for a little over over a mile and a quarter.

It's a nice four lane public road and one of the few places left where you can still drive fast and fairly safe (going upward anyways).

Parts of California have very hilly (and beautiful) areas.

 

Not being sarcastic by any means but i can use some help in math! ur uncertainties are good!

Not sure I understand

 

Fits my experience, the MFD is about 2% high. That is not a 'per tank' number, but a lifetime. If I graph my lifetime MFD weighted averages (ie, takes into account the number of miles and the avg) and my real lifetime (Actual gallons purhased and miles driven) for ~22K miles, it settles out at about 2%. There are the occasional anomolies where the MFD value is higher or lower than the 'pumped in' calculation for a particular tank. I attribute this to either the pump (without knowing it's accuracy) or whether I decided to round up or down to more round $$ for that purchase.

Another thing that could affect the actual vs MFD lifetime: I replaced the Goodyear Integrities (855 Revs/mile) with Goodyear TripleTreds (863 revs/mile) after about 4 months. I THINK that would affect the MFD calculation toward a very slightly higher MPG value since it 'thinks' I went slightly farther than I really did. When you are getting 500 miles on a tank, those extra 7 revs/mile do add up. Of course, that should also affect the odometer so maybe the 'actual' calc is equally affected? So maybe it really just explains why I get a little more gas in when I fill compared to the number of gallons I have presumably used based on the # of miles and the MFD average.

 

I've been filling up at different stations. When the pump stops, I stop pumping. I have found that with the exception of my first fill-up the Camry's reading has been 0.8 to 1.0 mpg higher than my calculated average.

When you manually measure your mileage you're working with large numbers (500 - 650 miles & 13 - 16 gallons). An error of a few ounces, which would be a high error for a gas pump, would not make a large difference in your calculated mpg. When sensors in the car are measuring your gas usage they're working with extremely small amounts of fuel. The sensors have to convert the fuel usage into digital readings. Errors due to rounding in the least significant bits (LSBs), although small, could probably cumulatively add up to a larger error.

The only flaw to this logic is that rounding errors should offset; some should be low and some should be high. Theoretically it should round to zero. However, most people seem to be reporting higher mpg on the Camry display than calculated. That I can't explain.

 

What do think about re-calibrating the tires in the NAV system.... Will that help - maybe it was really never calibrated in the first place...

 

What do think about re-calibrating the tires in the NAV system.... Will that help - maybe it was really never calibrated in the first place...

Is that possible? I wonder why they put 60 series tires on these in the first place. I wonder if the speedo was not calibrated for 215 / 65 series tires which would make it about right.

(I guess if we put 85 series truck tires on these we could increase our warranty coverage by a 1000 miles or so)

 

AFAIK, it's only for the navi system where you can't get signals from the GPS.
The mileage or odometer value does not change.

Ken@Japan