Fuel Tank Capacity

Tom6850 · 03-30-2007, 07:58 AM

This may have been addressed in the past, but I have a question on the fuel tank bladder. My MFD displayed 52.4MPG, when I filled the tank to the first shut off, the actual MPG was 44.5 MPG. I think that some of the difference might be in the fuel tank bladder increasing in size due to higher temperatures in the past 2 weeks.

Does anyone know the ambient temperature for the tank to hold 11.9 gallons? Also has anyone come with a chart showing the size of the bladder for every 10 or 15 degree change in temperature? Maybe TonyPShafer charted this, his spreadsheets are really detailed.

brick · 03-30-2007, 12:10 PM

You've got it right. It got warmer here and I finally found a pump that works with the tank bladder to give me a decent fill. That turned 56mpg+ on the MFD into 42mpg by hand calculations. No worries, it doesn't matter. But as for a correlation of capacity vs. temp, I think the answer is "in theory only." The problem with rubber is that its flexibility and elasticity change with the temperature, with age, with the number of cycles through which it has been used, and maybe even other factors like small variations in material composition from one tank to another. So what is valid for one guys '04 probably isn't much help for our less-used '07s.

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03-30-2007, 07:58 AM	#1
Tom6850 Retired Join Date: Feb 2007 Location: Macungie, Pa Posts: 891 My Car: 2007 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 1	This may have been addressed in the past, but I have a question on the fuel tank bladder. My MFD displayed 52.4MPG, when I filled the tank to the first shut off, the actual MPG was 44.5 MPG. I think that some of the difference might be in the fuel tank bladder increasing in size due to higher temperatures in the past 2 weeks. Does anyone know the ambient temperature for the tank to hold 11.9 gallons? Also has anyone come with a chart showing the size of the bladder for every 10 or 15 degree change in temperature? Maybe TonyPShafer charted this, his spreadsheets are really detailed.

03-30-2007, 12:10 PM	#2
brick Senior Member Join Date: Dec 2006 Location: Columbia, SC Posts: 720 My Car: 2007 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	You've got it right. It got warmer here and I finally found a pump that works with the tank bladder to give me a decent fill. That turned 56mpg+ on the MFD into 42mpg by hand calculations. No worries, it doesn't matter. But as for a correlation of capacity vs. temp, I think the answer is "in theory only." The problem with rubber is that its flexibility and elasticity change with the temperature, with age, with the number of cycles through which it has been used, and maybe even other factors like small variations in material composition from one tank to another. So what is valid for one guys '04 probably isn't much help for our less-used '07s.