MPG Tip - Toyota Yaris Forums

bronsin · 03-22-2013, 08:15 AM

I got this from a post on my motorcycles forum:

One of the most important tips is to fill up when your gas tank is HALF FULL. The reason for this is the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.

nookandcrannycar · 03-22-2013, 07:47 PM

Quote:

Originally Posted by bronsin

I got this from a post on my motorcycles forum:

One of the most important tips is to fill up when your gas tank is HALF FULL. The reason for this is the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.

I have no doubt that what you are reporting is true but, depending on the person, not doing this (and waiting until you are close to empty) may trigger other behaviors that in total more than offset the evaporation (taking routes that have fewer signals and more right turns (which is getting harder to do in my neck of the woods), monitoring tire PSI more closely, driving even more gingerly, doing errands in off peak hours when possible, having more time and more miles to correct for not having done these things and things like having gotten stuck in construction traffic, etc.).

Anecdotally, I see an inkling of what you're saying when I do less driving and take longer to 'go through' a tank. On those tanks (ones that say, don't get to empty for 2 weeks or so) it seems to be harder to get over 40 combined on a tank, where it is usually routine.

bronsin · 03-23-2013, 02:45 AM

Im not saying it just reporting it for comment. Maybe its so. But I dont think air can get into a gas tank very much for the gas to evap into. Theres charcoal filters to trap it anyway. Whether that works is another story.

What I cant BELIEVE is that people wait until the tank is empty to fill it up! Good way to run out of gas! And they TRUST that idiot blinking light! Like you Im dubious this saves fuel but if it helps people to not run their tank dry before filling up its all good.

MAybe manufactures should incorporate a floating cover for the gas inside the gas tank like the ones in gas station tanks?

MAybe Prius will do it to go along with all thier other nit wit features.

tooter · 03-23-2013, 10:49 AM

I don't think that the half tank makes a difference because our cars run (partially) on those gas tank vapors from being pulled into the engine by manifold vacuum to be burned. That's the whole idea of the tank's sealed vapor recovery system. I do know that you don't want to run the tank dry as that can damage the fuel pump.

BEEF · 03-23-2013, 12:09 PM

I am not a motorcycle driver or owner but they probably don't have an evap recovery system.

This may be valid on a bike but I can't see the validity on a car (or at least newer ones).

I also think running the fuel down isn't bad. I know about how many miles I can go on a tank and fill accordingly. I usually have a gallon or so left in the tank (which is roughly 40 more miles). I tend to fill up at least once weekly (actually my other car) and couldn't imagine filling twice a week just for the added time it takes. I drive around 500 miles weekly so I am probably not the norm.

bronsin · 03-23-2013, 12:44 PM

My 1996 BMW R11GS had a charcoal filter to trap gas as does my 2004 ST13.

mr_miles · 03-23-2013, 06:41 PM

Quote:

Originally Posted by BEEF

I also think running the fuel down isn't bad. I know about how many miles I can go on a tank and fill accordingly. I usually have a gallon or so left in the tank (which is roughly 40 more miles). I tend to fill up at least once weekly (actually my other car) and couldn't imagine filling twice a week just for the added time it takes. I drive around 500 miles weekly so I am probably not the norm.

Ditto, sounds like we do the same, lol. I keep my trip meter on display all the time and I reset it every fill up to calculate :)

nookandcrannycar · 03-23-2013, 08:11 PM

Quote:

Originally Posted by bronsin

And they TRUST that idiot blinking light!

I don't. I, like Mad Max, keep a close eye on how many miles I've traveled on the current tank and know from experience the minimum amount I can count on from how my Yaris has performed in the past.. I also include (a little bit) the bar drop interval for that particular tank. This method has proven to be very accurate in my case.

Quote:

MAybe Prius will do it to go along with all thier other nit wit features.

nookandcrannycar · 03-23-2013, 08:16 PM

Quote:

Originally Posted by BEEF

I know about how many miles I can go on a tank and fill accordingly.

nookandcrannycar · 03-23-2013, 08:18 PM

Quote:

Originally Posted by mr_miles

I keep my trip meter on display all the time and I reset it every fill up to calculate :)

I also do the same.

tooter · 03-23-2013, 09:38 PM

Quote:

Originally Posted by BEEF

I am not a motorcycle driver or owner but they probably don't have an evap recovery system.

Mine did, but it was one of the first thinge that got removed because if you tip the bike over, the cannister gets flooded with fuel and you can't restart the engine.

Quote:

This may be valid on a bike but I can't see the validity on a car (or at least newer ones).

You're right. The tanks are sealed systems.

03-22-2013, 08:15 AM	#1
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	MPG Tip I got this from a post on my motorcycles forum: One of the most important tips is to fill up when your gas tank is HALF FULL. The reason for this is the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount. __________________ Synthetic Oil: Its All In Your Head

03-23-2013, 02:45 AM	#3
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	Im not saying it just reporting it for comment. Maybe its so. But I dont think air can get into a gas tank very much for the gas to evap into. Theres charcoal filters to trap it anyway. Whether that works is another story. What I cant BELIEVE is that people wait until the tank is empty to fill it up! Good way to run out of gas! And they TRUST that idiot blinking light! Like you Im dubious this saves fuel but if it helps people to not run their tank dry before filling up its all good. MAybe manufactures should incorporate a floating cover for the gas inside the gas tank like the ones in gas station tanks? MAybe Prius will do it to go along with all thier other nit wit features. __________________ Synthetic Oil: Its All In Your Head

03-23-2013, 12:09 PM	#5
BEEF View User's Garage Drives: 2008 yaris 3d Join Date: Apr 2011 Location: north carolina Posts: 732	I am not a motorcycle driver or owner but they probably don't have an evap recovery system. This may be valid on a bike but I can't see the validity on a car (or at least newer ones). I also think running the fuel down isn't bad. I know about how many miles I can go on a tank and fill accordingly. I usually have a gallon or so left in the tank (which is roughly 40 more miles). I tend to fill up at least once weekly (actually my other car) and couldn't imagine filling twice a week just for the added time it takes. I drive around 500 miles weekly so I am probably not the norm. __________________ Be the change you wish to see in the world -Mahatma Gandhi-

03-23-2013, 12:44 PM	#6
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	My 1996 BMW R11GS had a charcoal filter to trap gas as does my 2004 ST13. __________________ Synthetic Oil: Its All In Your Head

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03-23-2013, 10:49 AM	#4
tooter play every day Drives: 2012 Yaris L 2dr 5sp Join Date: Apr 2012 Location: Los Angeles Posts: 1,961	I don't think that the half tank makes a difference because our cars run (partially) on those gas tank vapors from being pulled into the engine by manifold vacuum to be burned. That's the whole idea of the tank's sealed vapor recovery system. I do know that you don't want to run the tank dry as that can damage the fuel pump.