Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
What gives ?
Is this normal ?
My previous experiences with car computer calculated mpg figures found them fairly accurate.
Some of them seem to give you a predicted range based on how you are driving it right "now" rather than based on longer term sampling. We had a loan car a while back that was similar (so unremarkable I can't even recall what it was!). But that did a similar trick. Coasted down a road and it said you were doing 85mpg, gave it some welly and it said 15mpg. The range prediction seemed to be based on that figure multiplied by the estimated fuel remaining.
I managed to get 1.2mpg out of the van yesterday - although that was on my way home to fix a battery/charging fault, and electrical gremlins seem to play havoc with its computer system(s). At least the dash display didn't start up in Spanish this time... :-)
but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
Our '56 Jazz' consumption gauge seems to be both accurate overall and sensitive to driving conditions at each moment. We don't see over 55 though, but if it was as low as 35 I'd be looking for flat tyres.
but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
fairly accurate.
In my experience, there's a lot of variability in when petrol station pumps decide that the tank is full and cut off. I reckon the variation is could be up to 2 litres between fills for my car. I'm reasonably condfident of this, because I've recorded every fuel purchase I've made in the last 14 years in a spreadsheet and used it calculate MPG... maybe I need a hobby.
Also, did you fill the tank yourself when accepting the car, or did the supplier put just enough fuel in it to make the gauge read "full" ?
but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
fairly accurate.
Did you reset the MPG calc when you got the car? Otherwise, it will show the average since it was last reset. If previous users were less heavy-footed ....
IIRC on my Jazzs the mpg is reset when you reset the trip odo
Hehe!
I reset the Average MPG on my (brilliant) Torque Pro Android ODB app and OBD BT dongle and even doing just a few miles it was back up to around 36 mpg again (it was around 31 mpg when the thermostat was opening too early and the engine was being overcooled). I think it was around 38 mpg after a few hundred miles of mixed driving and pre the reset.
Of course the instantaneous figures are all over the place but the average seems to fit very closely with the figures seen here:
For the Jazz it shows between 48 and 55 for the Hybrid.
Probably used US Gallons in the software... grin. Brian
About 20 years ago I was a passenger in a big BMW that had an analogue consumption meter. When it was booted hard the needle dropped below zero - I still haven't worked out the implications of that.
Yes, it probably varies from car to car. On my Volvo, you specifically have to tell it to reset the mpg counter. Otherwise, it just goes on forever.
Sounds to me like you have a hobby :-)
No it has a live consumption read out as well as calculated range remaining
mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
them fairly accurate.
Tank was reading empty when I put about 2.5 gallons in. 80-88 miles later I had the orange light on again.
Because its a loaner for an indefinite period whilst my own car is being repaired I was initially loath to fill it.
Sounds like very poor design. The two have different functions. Many like to know the ongoing average fuel consumption.
I suspect the only sensible way to test it is fill-er-up, run for a large number of miles, then fill-er-up again. MPG is miles driven over second gallons added.
FWIW my Zafira starts blinking the fuel light very early so if that is your "used all the fuel" indicator, it won't mean "used 2.5 gals".
Paul DS.
had the orange light on again.
That's going to be massively inaccurate, easily enough to account for the discrepancy you're seeing.
later I had the orange light on again.
I dunno. According to the computer I should have been seeing close to 150 m= iles of usage. 80-88 is a long way off that. I tend to refill as soon as th= e reminder light flickers so discrepancy there would not be large. Anyway I= wouldn't imagine the Jazz has a huge reserve as the tank appears to be ver= y small compared to my usual car
I think this will depend on the car, and the design of the fuel tank.
For example, the length of the pipe between tank and cap. On an original Mini there's virtually no pipe, so possibility of significant differences between fill-ups greater. If you're only filling the pipe, as on (AIUI) most modern cars, less variability.
Rob
"Gallons per mile"
:-)
Scott
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