"Letting your gas tank get below 1/3 full will cost you MPG"-Myth? - Toyota Yaris Forums

dchurchwell · 04-25-2011, 01:53 PM

I've read that letting the gas tank get below 1/3 full can cause you to lose MPG when you go around turns. Supposedly your gas will not go to the engine if it is being slung to the side? I do not know much about cars, am relatively new to hypermiling, and deliver pizzas (lots of hard 90 degree turns at highest possible speed). Thoughts?

SKurj · 04-25-2011, 01:55 PM

electric fuel pumps..

dchurchwell · 04-25-2011, 02:07 PM

are you saying this is a myth? like i stated, i don't now much about cars, and certainly not what an electric fuel pump does

Altitude · 04-25-2011, 04:01 PM

Never heard that one before. But the premise is all wrong. If gas is getting slung up to the side and is not making it to the pump, then you're actually using no gas, which is good for MPG. Worst that could happen is that you get an air bubble in the fuel lines which might make the car hiccup.

Of course if you are driving in circles at high speed and the fuel is permanently slung to the side of the tank, that's a different story altogether.

STC · 04-25-2011, 04:36 PM

Hmmm? Never heard that? I always thought letting your tank go well under 1/8 all the time 'could' cause your fuel pump to go early? The fuel pump is inside the gas tank...

Cheers!

SKurj · 04-25-2011, 06:25 PM

Quote:

Originally Posted by STC

Hmmm? Never heard that? I always thought letting your tank go well under 1/8 all the time 'could' cause your fuel pump to go early? The fuel pump is inside the gas tank...

Cheers!

Yes now that one i have heard, let the tank run real low and the pump is no longer submerged therefor getting hot... but i dunno if the yaris has an in tank pump or not..

sickpuppy1 · 04-25-2011, 06:38 PM

And also, with the temp changes this time of year, you are much more prone to getting condensation in the tank. The more air (with moisture trapped in it) in the tank is subject to cold-hot changes make it more prone to picking up moisture in the tank.

thebarber · 04-25-2011, 09:33 PM

ive only heard that letting your tank run lower than 1/4 tank consistently over the life of the car will cause premature fuel pump wear.....im going to play it on the safe side, personally.

dobbiedoo · 06-02-2011, 12:12 PM

The tank has baffles built in, so there is never a chance of gas not being around the pump. As mentioned before the pump can overheat with a really low level of gas, shortening it life.

malibuguy · 06-02-2011, 12:28 PM

our cars have pulse fired fuel pumps...i'm not worried about it

hell, most of my "fun corners" are when i'm doing some EOC (engine off coasting)

R2D2 · 06-03-2011, 08:21 AM

Malibuguy,

Can you describe a pulse fired FP for me? I haven't heard the the term before and I'm unfamiliar.

What are the advantages?

Thanks in advance,

R2

malibuguy · 06-03-2011, 01:08 PM

for at least toyotas small cars (in terms of the years i'm referring to)

'97 & later Tercel, Echo, Yaris feature returnless fuel systems to reduce the heat thats introduced into the fuel being pumped up to the rail (soaking up heat there from the engine bay) then back to the tank. Going to returnless reduces evaporative emissions which is also aids in mileage. The fuel pumps are pulse fired to maintain rail pressure, since they can't be run all the time.

does that make sense? let me know...i'm kinda of crappy at explaining things

R2D2 · 06-03-2011, 08:03 PM

Nope, makes perfect sense, thank you! I never thought about the returnless aspect of the fuel system needing a different type pump. I see what you're saying.

These seem to be reliable units-at least I haven't heard of any problems?

My last vehicle my Dad aand I got really good at dropping the tank, if you know what I mean!

Thank you,

R2

malibuguy · 06-04-2011, 08:14 AM

my tercel chassis has about 210-215k on it, still original fuel pump...but i did have to replace the tank cuz it rotted out from being a NE car

all cars by now are returnless

JumpmanYaris · 06-04-2011, 08:22 AM

This was on Mythbusters and it was busted.
If you don't know what I am talking about (proven wrong)

daf62757 · 06-04-2011, 10:24 AM

Wouldn't the tank with less volume actually be lighter and get better mileage from less weight?

rick996 · 06-05-2011, 11:33 AM

Quote:

Originally Posted by daf62757

Wouldn't the tank with less volume actually be lighter and get better mileage from less weight?

Yes

Idahotom · 06-05-2011, 02:13 PM

I wait as long as possible to fillup. Partly because hauling less dead weight around is always a good thing, and partly because when I calculate my mileage after the fillup I want the biggest numbers possible for the most accurate determination of how I did that tank.

Just because the fuel pump is normally submerged, does not mean running low levels of fuel are harmfull, I gotta think they take guys like me into account when they design the things! I don't worry about my fuel pump in other words.

04-25-2011, 01:53 PM	#1
dchurchwell Pizza D Drives: 2007 yaris 3D MT Join Date: Apr 2011 Location: US Posts: 10	"Letting your gas tank get below 1/3 full will cost you MPG"-Myth? I've read that letting the gas tank get below 1/3 full can cause you to lose MPG when you go around turns. Supposedly your gas will not go to the engine if it is being slung to the side? I do not know much about cars, am relatively new to hypermiling, and deliver pizzas (lots of hard 90 degree turns at highest possible speed). Thoughts?

04-25-2011, 04:36 PM	#5
STC "LibertyRides!" View User's Garage Drives: 2010 Yaris 3Dr LB \| 2020 Stang Join Date: Mar 2010 Location: State College, PA, USA Posts: 576	Hmmm? Never heard that? I always thought letting your tank go well under 1/8 all the time 'could' cause your fuel pump to go early? The fuel pump is inside the gas tank... Cheers! __________________ ~ Mark ~ 2010 Yaris 3-Dr Liftback, 5-Speed Manual, P185/60R 15, Bayou Blue Pearl I Love my YARIS - (Click below to see Gaslog): Most miles Tank: 538 tank/10.148 gal = 53.015 MPG / Most MPG: 54.95 MPG (ethanol) 425 tank/7.73 gal "The evils of government are directly proportional to the tolerance of the people." -- Frank Kent

04-25-2011, 06:38 PM	#7
sickpuppy1 Drives: 2010 Yaris Sedan Join Date: Feb 2010 Location: Kansas Posts: 871	And also, with the temp changes this time of year, you are much more prone to getting condensation in the tank. The more air (with moisture trapped in it) in the tank is subject to cold-hot changes make it more prone to picking up moisture in the tank. __________________

04-25-2011, 09:33 PM	#8
thebarber daily driver View User's Garage Drives: the #wrecho Join Date: Jun 2006 Location: Grand Rapids, MI Posts: 5,877	ive only heard that letting your tank run lower than 1/4 tank consistently over the life of the car will cause premature fuel pump wear.....im going to play it on the safe side, personally. __________________

06-02-2011, 12:28 PM	#10
malibuguy Obsessed with 1.5L Drives: '10 PW Yaris Sedan Join Date: Feb 2011 Location: Westminster, MD Posts: 907	our cars have pulse fired fuel pumps...i'm not worried about it hell, most of my "fun corners" are when i'm doing some EOC (engine off coasting) __________________ -Greg...the Exhaust Freak. -10 PW sedan 107whp/110wtq, full exhaust, suspension bits, TRD LSD -06 Highlander 3mzfe Limited AWD -82 Malibu, 1uzfe swap -97 Tercel coupe, 1nzfe/4.31 -96 Tercel coupe, Turbo 5efe, autoX -96 Tercel 4dr

04-25-2011, 01:55 PM	#2
SKurj Drives: 09 Yaris 3dr HB, BRZ Join Date: Mar 2011 Location: GTA Posts: 222	electric fuel pumps..

04-25-2011, 02:07 PM	#3
dchurchwell Pizza D Drives: 2007 yaris 3D MT Join Date: Apr 2011 Location: US Posts: 10	are you saying this is a myth? like i stated, i don't now much about cars, and certainly not what an electric fuel pump does

04-25-2011, 04:01 PM	#4
Altitude Drives: '08 LB MT Bayou Join Date: Oct 2008 Location: Colorado Posts: 1,671	Never heard that one before. But the premise is all wrong. If gas is getting slung up to the side and is not making it to the pump, then you're actually using no gas, which is good for MPG. Worst that could happen is that you get an air bubble in the fuel lines which might make the car hiccup. Of course if you are driving in circles at high speed and the fuel is permanently slung to the side of the tank, that's a different story altogether.

06-02-2011, 12:12 PM	#9
dobbiedoo Dobbiedoo Drives: 2009 5 door Hb Yaris Join Date: Aug 2010 Location: Stoughton,Ma Posts: 36	The tank has baffles built in, so there is never a chance of gas not being around the pump. As mentioned before the pump can overheat with a really low level of gas, shortening it life.

06-03-2011, 08:21 AM	#11
R2D2 Crazy Oil Sniffer Drives: MM 09 Yaris 5 Dr LB "Click" Join Date: May 2009 Location: ME Posts: 498	Malibuguy, Can you describe a pulse fired FP for me? I haven't heard the the term before and I'm unfamiliar. What are the advantages? Thanks in advance, R2 __________________ "The howl was the sound of God’s casting pot, the morphing of my cells into shape, the forming of oceans out of molten premordial plasma. And I could feel it. I could cry for it. I could cry with it." -The Fitful One

06-03-2011, 01:08 PM	#12
malibuguy Obsessed with 1.5L Drives: '10 PW Yaris Sedan Join Date: Feb 2011 Location: Westminster, MD Posts: 907	for at least toyotas small cars (in terms of the years i'm referring to) '97 & later Tercel, Echo, Yaris feature returnless fuel systems to reduce the heat thats introduced into the fuel being pumped up to the rail (soaking up heat there from the engine bay) then back to the tank. Going to returnless reduces evaporative emissions which is also aids in mileage. The fuel pumps are pulse fired to maintain rail pressure, since they can't be run all the time. does that make sense? let me know...i'm kinda of crappy at explaining things __________________ -Greg...the Exhaust Freak. -10 PW sedan 107whp/110wtq, full exhaust, suspension bits, TRD LSD -06 Highlander 3mzfe Limited AWD -82 Malibu, 1uzfe swap -97 Tercel coupe, 1nzfe/4.31 -96 Tercel coupe, Turbo 5efe, autoX -96 Tercel 4dr

06-03-2011, 08:03 PM	#13
R2D2 Crazy Oil Sniffer Drives: MM 09 Yaris 5 Dr LB "Click" Join Date: May 2009 Location: ME Posts: 498	Nope, makes perfect sense, thank you! I never thought about the returnless aspect of the fuel system needing a different type pump. I see what you're saying. These seem to be reliable units-at least I haven't heard of any problems? My last vehicle my Dad aand I got really good at dropping the tank, if you know what I mean! Thank you, R2 __________________ "The howl was the sound of God’s casting pot, the morphing of my cells into shape, the forming of oceans out of molten premordial plasma. And I could feel it. I could cry for it. I could cry with it." -The Fitful One

06-04-2011, 08:14 AM	#14
malibuguy Obsessed with 1.5L Drives: '10 PW Yaris Sedan Join Date: Feb 2011 Location: Westminster, MD Posts: 907	my tercel chassis has about 210-215k on it, still original fuel pump...but i did have to replace the tank cuz it rotted out from being a NE car all cars by now are returnless __________________ -Greg...the Exhaust Freak. -10 PW sedan 107whp/110wtq, full exhaust, suspension bits, TRD LSD -06 Highlander 3mzfe Limited AWD -82 Malibu, 1uzfe swap -97 Tercel coupe, 1nzfe/4.31 -96 Tercel coupe, Turbo 5efe, autoX -96 Tercel 4dr

06-04-2011, 10:24 AM	#16
daf62757 Nothing beats a Toyota! View User's Garage Drives: 2013 Yaris 5 dr liftback Join Date: Jan 2009 Location: Indianapolis, Indiana Posts: 564	Wouldn't the tank with less volume actually be lighter and get better mileage from less weight? __________________ Big Dave Indianapolis, IN Synthetic Oil....its in my car.....for at least 10,000 miles!

06-05-2011, 02:13 PM	#18
Idahotom Drives: 2008 5 sp. LB Join Date: Oct 2010 Location: Idahoi Posts: 268	I wait as long as possible to fillup. Partly because hauling less dead weight around is always a good thing, and partly because when I calculate my mileage after the fillup I want the biggest numbers possible for the most accurate determination of how I did that tank. Just because the fuel pump is normally submerged, does not mean running low levels of fuel are harmfull, I gotta think they take guys like me into account when they design the things! I don't worry about my fuel pump in other words.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Fuel Economy	swng	Fuel Economy Forum	2089	01-23-2015 06:41 PM
Free gas for any vehicle.	ketel0ne	General Yaris / Vitz Discussion	4	09-19-2006 08:07 AM
Full Gas Tank Noise?	hoahmaru	General Yaris / Vitz Discussion	8	04-10-2006 12:17 AM