Filling Up Full Tank Adds Unnecessary Weight Thus Reduces Mpg.

[euromodder]

It may be an old thread, but I'm going to give this a try !

If I only fill up to half-tank, that means having 26L (diesel) or 21.8 kg less weight on the car.
That's about the combined weight improvement from dumping the spare and my own weight loss
There are some more potential weight gains as well, so I'm going to combine all of them and see what gives.

My favourite fuel station is right on my commute - a detour of only 25m (or less than 30 yards) and 1 extra stop.

Also, my car has no issues when the tanks level drops - when it gets really low (about 3L from empty) the engine performance will automatically be reduced to conserve gas.
Even when run dry, the fuelsystem will refill itself when fuel is added to the tank.

[evilskillit]

Originally Posted by euromodder

Even when run dry, the fuelsystem will refill itself when fuel is added to the tank.

Thats pretty cool. I've heard horror stories from my father in law about getting air out of a diesel fuel system if you run it empty. He used to be a tractor mechanic and was a mechanic in the military. Then again that was 20-30 years ago.

[johnlvs2run]

Unless I'm missing something, the chart was interpreted in reverse of results.

There was 62 mpg from average to maximum, and 52 mpg from average to minimum.

Therefore the mpg was 10 mpg higher when the tank was near full than near empty.

Originally Posted by PaleMelanesian

Q3 is the 75th percentile, or halfway from average to max.
Q1 is the 25th, or halfway from average to min.


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[Cd]

Originally Posted by RH77

I'm generally concerned about evaporate pollution from filling-up too often. We get quite a few "Ozone Alert" days in the Summer, so we know it's a problem. I let it get close to E and completely refill. Better for FE tracking too..
RH77

THANK YOU ! You took the words right out of my mouth.

Ironically, I was just about to post a dedicated thread on this very topic ( evaporative emissions from your gas tank every time you open it. )

As far as the topic of gas tank size, I have often wished that I had a 5 gallon tank, since the 11.9 gallon tank sometimes takes me months to go through.

[PaleMelanesian]

Originally Posted by johnlvs2run

Unless I'm missing something, the chart was interpreted in reverse of results.

There was 62 mpg from average to maximum, and 52 mpg from average to minimum.

Therefore the mpg was 10 mpg higher when the tank was near full than near empty.

I think you're reading it wrong. Look at the green line. That's the average result. The others are to show statistical variation, but the trend holds true.

Green line (average): 59 mpg at 1/4 tank, vs ~55 mpg at Full+. Better mpg with less fuel.

Ignore the 1% number. My car has a problem with fuel pressure when the tank gets low.