Hi

Has anyone one here done a reliable test on their MPG? Am currently benchmarking using the fill to brim, drive 100 miles or so, return to same pump, fill to brim method. Its currently looking like I'm achieving about 15mpg in congested urban driving!! Car has been serviced with new air filter etc, tyre pressure is good. Was expecting about 18-20 mpg around town to be honest.

Anyone else have any mpg statistics?

cheers

 

Couple thoughts about the measurement uncertainty of your method...

Drive farther than 100 miles, then you're putting in more fuel on each fillup. You can easily calculate MPG by dividing (miles)/(gallons).

Repeat this over several tankfuls of fuel. Add up ALL the fuel & ALL the miles. So your calculation can cover a few thousand miles. That way you get a better average over your driving habits, not just that one particular 100-mile trip.

Don't fill "to the brim". The vapor-recovery hose on the gas pump might be sucking fuel back into the gas station's vapor-recovery system. You've paid for that fuel, and you're including it in your MPG calculation. Try to reasonable fill each time to a repeatable point, for example stop at the 1st click of the nozzle. Then you only have to go back to the original pump at the very end of the series.

 

I second Jim's comments, don't ever fill to the brim, not only will you waste fuel, but you can seriously damage the evap/vapor recovery system.

To develop a good baseline for fuel economy you should fill to where the pump clicks off, and measure for five consecutive tanks of fuel.

One other thought, fifteen miles per gallon when driving in heavily congested traffic conditions isn't at all out of the ordinary, regardless of the car. Think about it, even a Civic will get less than ten miles per gallon given enough idling in heavy traffic.

 

Thanks for the replies. I should have been clearer 'to the brim' I actually mean to the 'cut off' as you suggested

@Shipo you are probably right. Most of the benchmarking is done in heavy stop start traffic. 35 minutes to drive 5.5 miles is an indicator of what my morning commute involves. I'd say 20% of this time is spent stationary. Plus, I often take my lunch break by driving a mile to the sandwich bar and being so bloody cold at the moment, will run the engine for 5 minutes whilst I sit in the car and eat/read the paper.

'Official' figure for this car is around 18.8mpg urban, but I bet thats not calculated on a crawl to work!

 

like above, my similar observation is that mpg calcs, based on less than a 1/2 tank fill, will be unreliable.

 

I've had MPG variations from tank to tank, but if you record miles & gallons over a number of CONSECUTIVE fillups, it just gets more & more accurate.

 

Initial test indicates 17.7 mpg which isn't too bad at all for heavy urban rush hour traffic only.

Will carry on testing over the next month or so and also try a 'highway' calculation too.

Out of interest does the US use 'Imperial' or 'US' gallons these days? In theory you should get about 15% more miles out of an imperial gallon.

 

The United States uses the "US" gallon; the Imperial gallon is used in Canada as a throwback to their pre-metric days, and is only used with any regularity in England (although I'm pretty sure I saw some gas stations in England using Liters as the unit of measurement).

 

We use litres to price our fuel and have done for some time now. Strange, as we still use miles per gallon for all of our economy statistics, although miles per litre is now creeping in here and there.

Just done some checking of fuel statistics online and its clear why some US manufacturers mpg figures seem rather poor. That only because most of us don't (me included up until now) don't realise the difference between a USG and an ImpG!

 

Imperial gallon is 20% bigger than US gallon.

What's cool is I can change the MPG display in my Saabs between "miles per US gallon" to "miles per imperial gallon". Instant 20% improvement!!!