There is definitely a problem with the angle of the vehicle - left to right, when filling up.

My indicated and calculated MPG's vary quite markedly depending on whether the car is on a slope down to to the filler side, or up to the filler side - and it doesn't need to be much of an angle either!

I can get several more litres in when the filler is on the high side...without even realising it.

This is throwing out my calculations by as much 0.5 L/100klm's (5 U.S. mpg)

Has anyone else noticed this?

 

All of the gas stations that I have used seem to be flat and level in the pumping area. With the gas nozzle fully inserted, the slant of the vehicle will change the effective volume (the point where the pump shuts off). I think the dash FE will be the more precise number. However, the calculated number (over many tanks) will be the more accurate number. The calculated FE will let you calculate a %error for the dash FE. So far, my dash reads 1.9% low.

It could be worse. The Prius has a bladder style gas tank that can lead to large tank to tank variations in calculated FE.

 

I think the problem has been a change of gas stations that I fill up at. The first one was level, this one is on a corner and for some reason there is a slope across the entire apron.


Prior to that I found that the dash FE was showing slighlty worse FE than when calculated - fine by me.

I have been steadily decreasing fuel consumption over the last 3 months according to the dash FE 5.7 - 5.6 - 5.5 - 5.4 and this last fill showed 5.3! But on fill up calculations it was 5.7!!!

On another occasion it was the reverse - and it just so happened that I was facing the other way on fill up! That is, the filler was downhill so I ended up putting less gas in.

While I've got you there, does ambient temperature make much difference to FE?

It's been fairly cool here for the last couple of months - 45 - 50 F.

 

The experts here say temperature makes a big difference in FE. The hotter the better (unless you are running the A/C a lot). Most people see a pretty big difference between winter and summer.

 

Yeha! Come on summer!

 

Aussie David;
It's been estimated that Winter temperatures decrease mpg by 10%. Of course, 45-50 degrees isn't bad compared to what I see here in New York State during the winter. It all comes down to how long the engine takes to get up to temperature and for the IMA to begin functioning.
Also, alot of the folks here will seek out the very same pump everytime they fill up so that the calculations will be more uniform. It eliminates one more variable from their figures. It certainly can make a difference as you've shown.

 

I think I get a double wammy in the morning too.

For the first 500 yards or so it's all uphill (dirt road), with a high speed country road merge/intersection/cross road. So -

1/ The engine is cold

2/ I've got to push it hard as well from that intersection - 0 - 60mph in 20 seconds or I'm dead!

3/ It's all uphill for at least a mile from that intersection as well.

4/ Then it's a 30miles of freeway (moving carpark).


It's really hard to make that up.

Nevertheless I'm still getting 45U.S. MPG (5.4 L/100klm) which I guess is not that bad.

Originally I thought I was doing really well because our gallon is 4.45L but your gallon is 3.785L - which is 52 AUS MPG.

But there are still some people on this forum that are getting 60 U.S. MPG and higher (Lakedude).

Unfknblvbl!

 

Wow! That is a double whammy! Fortunately for me I coast downhill for about a mile before I have to stop. Next it's accelerating onto a state road with a 55mph speed limit. Traffic isn't usually bad when I drive in to the office, so I don't often have to floor it to get up to speed. Another mile down the road and it drops down to 45mph anyway. Then , after a traffic signal it's back up to 55mph straight up a mile long hill. The hills are an mpg killer, but luckily for me I don't have to deal with bumper to bumper traffic on a daily basis. Just try to keep a buffer btw yourself and the driver ahead of you during the carpark phase of your commute and glide at a slow pace. (I'm sure you're trying to do this anyway since you are getting 45mpg.) Keep up the good work and pray for warmer days!