Gas Tank Reserve
08-18-04, 10:48 AM
#16
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Running on Empty
I have not run my gauge down quite that low, but to get an estimate for myself, I would wait until the gauge said exactly 1/4 left, and then I would fill it up. Each time I would notice that the amount of gas to fill the tank from 1/4 to full was several gallons less than 3/4 of the capacity of the tank (which is just under 20 gal, as I recall). My guess is that that last quarter of the gauge is pretty generous, because there seems to be more than a fourth of the volume left at that point, at least on my car (which is fine with me).
How accurate the needle is as it approaches the "E" I cannot say and hope to never find out.
Finally, given my MPG experience, I find the computer estimate of miles to go until empty to be very, very low.
How accurate the needle is as it approaches the "E" I cannot say and hope to never find out.
Finally, given my MPG experience, I find the computer estimate of miles to go until empty to be very, very low.
08-18-04, 06:22 PM
#17
That was great information Roofless. And thanks for doing the 'dirty' work for us man. It's rare you can trust either the computer or gauge, but I'm glad the computer is dead on, since it's the easier one to follow
I'll watch my tank go down to make sure the light comes on like yours.
Thanks again buddy.
I'll watch my tank go down to make sure the light comes on like yours.
Thanks again buddy.
08-18-04, 09:27 PM
#18
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Originally posted by Roofless
Yep. But keep in mind, the computer doesn't know how you're going to drive those last 50 miles or whether you'll be going up and down hills, etc. If I had kept it at a steady 65, I would have got pretty close to 50. I wanted to know when the light comes on, how far do I have driving the way I drive.
And yes, I was watching the gas gauge needle. At 50 miles, it looked like I would expect; it had a little ways to go. (It was right on the middle of the last peg before the E.) At 20 miles remaining, it looked like it was at the very end for sure, but it did go down a bit further. You can't tell where the end is, so the needle is not a good tool when you're getting close to fumes. However, having done this test I now know that the end on my gauge is the needle just touching the upper right corner of the E - same as when the car is turned off.
My test did reassure me that I could rely on the trip computer, as long as I understand the computer's limitations. Knowing I have 40 miles left when the light comes on is all I wanted to know. Well, I also wanted to know if zero miles was really zero miles. It is.
Yep. But keep in mind, the computer doesn't know how you're going to drive those last 50 miles or whether you'll be going up and down hills, etc. If I had kept it at a steady 65, I would have got pretty close to 50. I wanted to know when the light comes on, how far do I have driving the way I drive.
And yes, I was watching the gas gauge needle. At 50 miles, it looked like I would expect; it had a little ways to go. (It was right on the middle of the last peg before the E.) At 20 miles remaining, it looked like it was at the very end for sure, but it did go down a bit further. You can't tell where the end is, so the needle is not a good tool when you're getting close to fumes. However, having done this test I now know that the end on my gauge is the needle just touching the upper right corner of the E - same as when the car is turned off.
My test did reassure me that I could rely on the trip computer, as long as I understand the computer's limitations. Knowing I have 40 miles left when the light comes on is all I wanted to know. Well, I also wanted to know if zero miles was really zero miles. It is.
Roofless, when you filled the tank when the computer read zero, how many gallons did it take? The tank is supposed to hold 19.8 gallons. Mine takes 17.1 gallons.
Last edited by Umbo; 08-18-04 at 09:39 PM.
08-19-04, 08:29 AM
#19
Oh there was sputtering, baby! (ala George Castanza)
Umbo, sorry, you're right; I went from your Low Fuel warning to the warning light on my gauge. Sorry. I really couldn't comment on the Low Fuel warning, because I don't use it. But I had recently done this test and I thought a few could benefit by it. I figured you'd like the info too.
I doubt our cars are different, but maybe we're on to something. (I have a 2002 year model with a build date of 4/2001.) I can only speak of what I observed on my test here. Okay, warning "light' goes on, and I see the computer says I have 50 miles remaining. Gas gauge warning lights on most cars mean you have approximately 2 gallons left. (2 gallons x 25MPG = 50 miles.) Sounded logical to me.
Are you saying, the remaining miles goes down to zero, the Low Fuel "warning" comes on and that's when you're on Reserve? Does the remaining miles counter start over at 40-50 miles? If so, this is definitely not my experience. The Low Fuel warning was on during this time, but I didn't see when it went on. I mainly watched the miles remaining until I sputtered. I continued to sputter as I pulled into the pump. I've had my car long enough to know it doesn't sputter. And once I filled up, no more sputtering. So I was definitely sputtering from lack of fuel.
If what you're saying is the Low Fuel warning comes on way earlier than the light, such that you have 40 miles left before the light comes on, then I see what you're saying (and tfischer too.) Then my advice would be to use the light instead of the warning. And now you have some confirmation that the light does indeed indicate 2 gallons left.
Let me know if I'm close.
Oh yeah, the fill-up count. I forgot to look! I meant to too. There was a well-known character actor across the pump from me asking me questions about my car, and I spent the whole time trying to remember what I had last seen him in. I got 3 miles down the freeway and remembered I forgot to look. Actors!
Umbo, sorry, you're right; I went from your Low Fuel warning to the warning light on my gauge. Sorry. I really couldn't comment on the Low Fuel warning, because I don't use it. But I had recently done this test and I thought a few could benefit by it. I figured you'd like the info too.
I doubt our cars are different, but maybe we're on to something. (I have a 2002 year model with a build date of 4/2001.) I can only speak of what I observed on my test here. Okay, warning "light' goes on, and I see the computer says I have 50 miles remaining. Gas gauge warning lights on most cars mean you have approximately 2 gallons left. (2 gallons x 25MPG = 50 miles.) Sounded logical to me.
Are you saying, the remaining miles goes down to zero, the Low Fuel "warning" comes on and that's when you're on Reserve? Does the remaining miles counter start over at 40-50 miles? If so, this is definitely not my experience. The Low Fuel warning was on during this time, but I didn't see when it went on. I mainly watched the miles remaining until I sputtered. I continued to sputter as I pulled into the pump. I've had my car long enough to know it doesn't sputter. And once I filled up, no more sputtering. So I was definitely sputtering from lack of fuel.
If what you're saying is the Low Fuel warning comes on way earlier than the light, such that you have 40 miles left before the light comes on, then I see what you're saying (and tfischer too.) Then my advice would be to use the light instead of the warning. And now you have some confirmation that the light does indeed indicate 2 gallons left.
Let me know if I'm close.
Oh yeah, the fill-up count. I forgot to look! I meant to too. There was a well-known character actor across the pump from me asking me questions about my car, and I spent the whole time trying to remember what I had last seen him in. I got 3 miles down the freeway and remembered I forgot to look. Actors!
Last edited by Roofless; 08-19-04 at 08:46 AM.
08-19-04, 05:33 PM
#20
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Sorry I was ambiguous. All my comments are in reference to the computer on the center console. I don't even pay attention to the gas gauge or the idiot light. When the computer counts down to zero miles, it then starts flashing "low fuel". At that point there are still 2.7 gallons of gas in the tank. It is at that point that I set my trip odometer and drive another 15-20 miles without a sputter. Maybe the computer was changed to a more conservative setting on recent models. My SC is an '04. Let me know how many gallons your tank takes next time you have the inspiration to run her down to near empty.
Last edited by Umbo; 08-19-04 at 05:36 PM.
08-20-04, 02:54 PM
#21
Okay, the puzzle pieces came together and I see your point. (Would have been easier, had I not just done this test.) That is indeed very conservative. It does sound like we're different though. Had I known this conversation would take place and realized how important it was to get a gas fill-up count, I'd have told that actor to go take a wizz and buy a Jolt Cola, so I could concentrate on the task at hand. If I find myself in a similar situation, I'll get a fill-up count.
Incidentally, the actor was in the movie "The Game." He played the boss of the Game company. At least I came away with that...
Incidentally, the actor was in the movie "The Game." He played the boss of the Game company. At least I came away with that...
Last edited by Roofless; 08-20-04 at 03:15 PM.
08-20-04, 08:37 PM
#22
When I run my 02' down to 0 miles it takes
about 16 to 16.5 Gallons to fill it up.
19.5 full tank minus 16.5 to fill up equals
3 gallons left in tank when the computer
hits 0. Lead foot = 15 MPG = 45 miles to
out of gas. Feeway at 70 = 23 Mpg = 69 miles
to out of gas.
That my simple logic. Any one disagree.
about 16 to 16.5 Gallons to fill it up.
19.5 full tank minus 16.5 to fill up equals
3 gallons left in tank when the computer
hits 0. Lead foot = 15 MPG = 45 miles to
out of gas. Feeway at 70 = 23 Mpg = 69 miles
to out of gas.
That my simple logic. Any one disagree.
08-20-04, 09:48 PM
#23
I have one question. Total capacity is VERY different from useful capacity. Since modern fuel pumps have to run completely under fuel to avoid being burned, I bet the fuel pick-up pont is at a point just above that level. How much fuel is unused depends on size of fuel pump assembly and shape of tank. One last variable is accuracy of gas station's pumps, which to be fair, tend to overbill us.
Maybe one of the dealer techs here can answer the question specifically, but for now, my money is with Roofless (computer=0, you walk)... Until somebody proves him wrong
Maybe one of the dealer techs here can answer the question specifically, but for now, my money is with Roofless (computer=0, you walk)... Until somebody proves him wrong
08-21-04, 07:13 AM
#24
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My theory
Here's my theory for a happy motoring experience.
Computer = 1/4, you ride.
This has worked very well for me for over 3 years now, and the math is simple enough for me to do in my head.
Computer = 1/4, you ride.
This has worked very well for me for over 3 years now, and the math is simple enough for me to do in my head.
08-21-04, 07:25 AM
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Re: My theory
Originally posted by tfischer
Here's my theory for a happy motoring experience.
Computer = 1/4, you ride.
This has worked very well for me for over 3 years now, and the math is simple enough for me to do in my head.
Here's my theory for a happy motoring experience.
Computer = 1/4, you ride.
This has worked very well for me for over 3 years now, and the math is simple enough for me to do in my head.
08-21-04, 07:43 AM
#26
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Well roofless postulated that if computer = 0 you walk.
I postulate that walking is only done when the computer says 0, or "no ride." Thus walk = no ride. My theis is that if computer >0, a variable state ridability is available.
Since 1/4 > 0, then it would follow that 1/4 is not equeal to walk and, ipso fatso, 1/4=ride.
TaaaDaaaa!!
I postulate that walking is only done when the computer says 0, or "no ride." Thus walk = no ride. My theis is that if computer >0, a variable state ridability is available.
Since 1/4 > 0, then it would follow that 1/4 is not equeal to walk and, ipso fatso, 1/4=ride.
TaaaDaaaa!!
08-21-04, 10:49 AM
#28
I guess Fischer posture is never ride below 1/4 of a tank, which is a very good suggestion. I actually fuel up between 1/4 and 1/2 most of the time... at my convenience.
The 'miles to empty' debate is very interesting though, because knowledge is power I remember bringing home an '03 Vette from Dallas; I was close to home.The computer was throwing 28 mpg. That plus the computer 'range', the needle position, and the 18-gal capacity, mathematically I had fuel to spare. And by that I meant 80 miles left of range once I hit El Paso, so I avoided the long lines at the last fuel stop. Not so, my friends. Needle dropped like a rock, even though I was at the same pace, computer started recalculating range every second, and I made it to the first gas station in the city in fumes (car had sputtered TWICE already, and I responded by a sudden brake application, to slosh fuel over the gasping inlet hole). I knew 28 mpg on a big V8 was crap.. and I proved it
Lesson learned is it helps to know your car. And if you don't know it (like I didn't), DON'T PUSH IT. After that incident, I now fuel up on trips at the first stop below 1/2 tank, car or motorcycle; it helps to stretch the body and walk around a bit.
So what's the deal Roofless; are you going to run that sucker dry or what? You're being challenged, my friend!!! 
Prove them wrong!!
The 'miles to empty' debate is very interesting though, because knowledge is power
I remember bringing home an '03 Vette from Dallas; I was close to home.The computer was throwing 28 mpg. That plus the computer 'range', the needle position, and the 18-gal capacity, mathematically I had fuel to spare. And by that I meant 80 miles left of range once I hit El Paso, so I avoided the long lines at the last fuel stop. Not so, my friends. Needle dropped like a rock, even though I was at the same pace, computer started recalculating range every second, and I made it to the first gas station in the city in fumes (car had sputtered TWICE already, and I responded by a sudden brake application, to slosh fuel over the gasping inlet hole). I knew 28 mpg on a big V8 was crap.. and I proved it Lesson learned is it helps to know your car. And if you don't know it (like I didn't), DON'T PUSH IT. After that incident, I now fuel up on trips at the first stop below 1/2 tank, car or motorcycle; it helps to stretch the body and walk around a bit.
So what's the deal Roofless; are you going to run that sucker dry or what?
You're being challenged, my friend!!! Prove them wrong!!
08-21-04, 12:48 PM
#29
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ELP, if I'm interpreting correctly you are asking Roofless to run out of gas to prove that zero miles on the computer is actually zero miles. Do I have it right? As I've said before I have run the car 15 - 20 miles beyond the zero miles mark on 3 separate occasions without a problem.
08-21-04, 03:59 PM
#30
I believe he's taunting me. And I am VERY curious. We'll see.
I think Umbo is making the correct call. He's been down there more than any of us and watching his fuel counts. And Joe Peters has apparently been monitoring an excessive reserve too. I think what's at issue now is whether the earlier SC's had this reserve below zero miles. tfischer, feel like walkin' on the wild side? Okay... forget I said it.
The manual is of no help either - VERY vague. It says if either warning goes off, pull in for fuel. There's information overload at its worst.
I'll bet you a dollar Lexus put in this rather hidden excessive reserve to reduce the amount of calls to Roadside Assistance. Sneaky, but effective.
I think Umbo is making the correct call. He's been down there more than any of us and watching his fuel counts. And Joe Peters has apparently been monitoring an excessive reserve too. I think what's at issue now is whether the earlier SC's had this reserve below zero miles. tfischer, feel like walkin' on the wild side? Okay... forget I said it.
The manual is of no help either - VERY vague. It says if either warning goes off, pull in for fuel. There's information overload at its worst.
I'll bet you a dollar Lexus put in this rather hidden excessive reserve to reduce the amount of calls to Roadside Assistance. Sneaky, but effective.
Last edited by Roofless; 08-21-04 at 04:00 PM.