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OP here - interesting read on the thread. Just to re-iterate, I'm not concerned about how much the tank actually holds, the distance-to-empty (which is skewed to make sure you always have gas left), or even what mpg I'm getting.
I do use the same gas station every time, though not necessarily the same pump.
(and FYI I do the "update" on the trip mpg screen before I leave the station, so that every time I fill my instrument cluster is showing me the mpg on the current tank)
My only concern was that when I pull into the gas station and I've driven X miles since the last fill, and the car says I got Y mpg since the last reset, I should have to put in X/Y gallons to fill up again, but I always have to put in more (usually ~5% more) than that. You could say I'm overfilling, but unless the gas is leaking out somewhere, that would be impossible to happen every time! If I wasn't truly full when I started, then the next time I could put in more than the car burned, and I'd calculate less than the dash shows. But in that case, the prior time I would have calculated a higher mpg (like, if I drove to nearly empty, and only filled halfway up, I'd say WOW, I got 80 MPG on that tank because I drove 400 mi and only put in 5 gallons!)
Over a long period of time, it should average out and I'd be fine with it reading high one time and low another because of the difference in the pump shut-off or how much I squeeze in. But the car always claims I got 1-2 mpg more than reality, except for once which is not enough to make up for all the other times
Maybe this is evaporation? But if my car is evaporating 1/2 gal into the atmosphere every 3 weeks or so, isn't that a problem?
The inputs are not consistent enough to statistically and mathematically try to derive accuracy to tenths. The accuracy of the output calculations are only as good as that accuracy of the input data, SORRY
midcow3 - what are you talking about "the inputs"? I have the distance in miles to 3 significant digits, and the gallons to at least 3 significant digits, so I can divide them and be accurate with miles per gallon to 3 significant digits. Are you saying that 320 / 9.41 isn't 34.0 when rounded to the nearest 1/10th of a mpg?
And when 365 / 12.07 = 30.2, but the car claimed I got 32.2 mpg since the last fill-up, it doesn't take a rocket scientist to tell that something doesn't jive (and it's not my math).
FWIW, I graduated from M.I.T. and I have a Ph.D. Let me know if I don't know how to divide.
midcow3 - what are you talking about "the inputs"? I have the distance in miles to 3 significant digits, and the gallons to at least 3 significant digits, so I can divide them and be accurate with miles per gallon to 3 significant digits. Are you saying that 320 / 9.41 isn't 34.0 when rounded to the nearest 1/10th of a mpg?
And when 365 / 12.07 = 30.2, but the car claimed I got 32.2 mpg since the last fill-up, it doesn't take a rocket scientist to tell that something doesn't jive (and it's not my math).
FWIW, I graduated from M.I.T. and I have a Ph.D. Let me know if I don't know how to divide.
You are using inaccurate, inconsistent data even if it are three digits. I won't **** about degrees, I have multiple, but I am willing to be I know a lot more about and have a lot more experience in statistics and probabilities than you do.
By the way this has absolutely nothing to do with division, which I believe people still learn in the fifth grade.
Please explain to me how my data are inaccurate and inconsistent.
Are you claiming that the odometer is not telling me accurately how many miles I drove?
Are you claiming the pump is not telling me accurately how many gallons were pumped?
And, honestly, the miles driven shouldn't matter if it's slightly inaccurate (because of changes in tire circumference), because both the car's computer and my calculator are using the same numerator to calculate miles per gallon.
So, really, the issue is that when the car told me I drove 365 miles (3rd line from bottom) and that I got 32.2 mpg, it's saying I used 11.33 gal since the last time I completely filled the tank. So how was I able to pump 12.07 gallons in the next time? That's a nearly 1 gallon / 7% difference, and I doubt the pump is allowed to deviate that much (the gas station would be ripping everyone off).
The comment you link to is just an opinion of that guy. He gives no data to support what he says.
My last car was a 2010 Lexus RX350. I was the only driver. Every time I got gas, I let the pump shut off, then I added more gas until the 2nd shutoff. I did this for 14 years and >175,000 miles and never had to replace a "charcoal canister." In fact, I never had a single engine problem the whole time. My son is now driving the car and it drives like the day I bought it.
The comment you link to is just an opinion of that guy. He gives no data to support what he says.
My last car was a 2010 Lexus RX350. I was the only driver. Every time I got gas, I let the pump shut off, then I added more gas until the 2nd shutoff. I did this for 14 years and >175,000 miles and never had to replace a "charcoal canister." In fact, I never had a single engine problem the whole time. My son is now driving the car and it drives like the day I bought it.
Wow, second shut-off, I am sure that would give you 3 digit accuracy in filling up your gas tank, even if the second shutoff is not consistent based on the variance in gas batches, gasoline viscosity, ambient temperature, gas temperature, pump differences, season variances, slosh factor (even same pump can have different shut=off characteristics), etc. I also assume ( maybe that is a bad phrase) that you have never experienced an automatic shut-off failure; it is disastrous to see your gas tank overflowing and spewing gasoline to the ground.
By the way, most people are lucky and never hit the charcoal canister, so it is fairly low probability of destroying your charcoal canister. So if you feel lucky, then by all means ignore @Tinkertech 's advice.
By the way, if you are fueling to the second shut-off stop, you probably already realize that Lexus is very, very conservative on their DTE and fuel gauge bars. When DTE is zero(0) and goes blank and their are no more bars on you fuel gauge you still have somewhere between 2.75000 and 3.00000 gallons of gas left, Lexus refers to this as "reserve". So that means at the 39 mpg rate NX350h NX you could drive an additional 107.250 to 117.000 miles before you completely run out of gas. However, If you decide to test the "exact" size of your gas reserve, I would suggest taking a gas can with you to temporarily be able to put gas in your car to get to a service station.
Peace and Good Will my friend and an think my input to this subject is sadly nearing an asymptotic line of no return.
YMMV,
MidCow3
P.S. - One final parting thought. Most people think computers are very accurate and infallible. For the most part, that is a good assumption. But what if the Lexus computer that calculates mpg is not always accurate and is not dependent on just miles driven and gas consumed to calculate mpg. Or more likely what if the two parameters : (1) miles driven and (2) gasoline used are not always consistently and accurately fed to the Lexus mpg computer. Or egad , what idf Lexus techs had trouble with math and their calculation formula is 1 to 2 to 3 mpg off. Data Analytics is a ***** to understand.
It is just me providing my experience below. Sorry to make this thread longer...
My old RX can only go 300 miles before the next fuel stop. The display usually says around 350 miles range. I don't really care about the miles per gallon as I have a lead foot. But I am a little bothered that I have to refuel every 300 miles but not longer. So I try to squeeze more gas into the tank, not only stopping at the second auto pump stop. I lift the pump and pour the gas into the opening of the gas sometimes until it is overflowing - sorry - hurting the environment.
Maybe I have been lucky. I have never experienced the canister problem after almost 140,000 miles now. HOWEVER, I will stop doing this from now on as I learned from you that there MIGHT be a problem. And, by pouring more gas, I might be able to drive 5-10 or even 20 miles more out of 300 - it is a small fraction - I am OK either way. I will maybe at most stop the pump by the 2nd auto pump stop.
By the way, most people are lucky and never hit the charcoal canister, so it is fairly low probability of destroying your charcoal canister. So if you feel lucky, then by all means ignore @Tinkertech 's advice.
Peace and Good Will my friend and an think my input to this subject is sadly nearing an asymptotic line of no return.
YMMV,
MidCow3
Originally Posted by King2024
Peace to all!
It is just me providing my experience below. Sorry to make this thread longer...
My old RX can only go 300 miles before the next fuel stop. The display usually says around 350 miles range. I don't really care about the miles per gallon as I have a lead foot. But I am a little bothered that I have to refuel every 300 miles but not longer. So I try to squeeze more gas into the tank, not only stopping at the second auto pump stop. I lift the pump and pour the gas into the opening of the gas sometimes until it is overflowing - sorry - hurting the environment.
Maybe I have been lucky. I have never experienced the canister problem after almost 140,000 miles now. HOWEVER, I will stop doing this from now on as I learned from you that there MIGHT be a problem. And, by pouring more gas, I might be able to drive 5-10 or even 20 miles more out of 300 - it is a small fraction - I am OK either way. I will maybe at most stop the pump by the 2nd auto pump stop.
You all have a good weekend!
Originally Posted by tbartman67
The comment you link to is just an opinion of that guy. He gives no data to support what he says.
My last car was a 2010 Lexus RX350. I was the only driver. Every time I got gas, I let the pump shut off, then I added more gas until the 2nd shutoff. I did this for 14 years and >175,000 miles and never had to replace a "charcoal canister." In fact, I never had a single engine problem the whole time. My son is now driving the car and it drives like the day I bought it.
As @midcow3 mentions how this subject is nearing an asymptotic line of no return, I just want to build some reference into this. This topic of overfilling gas tanks and potential damage to the vapor canister seems to be a recurring concern, especially for Toyota and Lexus owners. While I can't personally comment on the overall credibility of CCN reviews, they have certainly built a reputation within the Toyota/Lexus community as a reliable source of information.
One of the recurring points he makes is the danger of overfilling your gas tank. According to CCN, this practice can lead to damage to the vapor canister, a component responsible for capturing and filtering gasoline vapors before they're released into the atmosphere.
It's important to acknowledge that this might not be a universal outcome. Some drivers might continue to overfill their tanks without experiencing any immediate problems. However, CCN emphasizes that it's a common issue, and the potential for costly repairs is a risk worth considering.
To delve deeper into this topic, you can check out his video titled "Never top off your tank"
This is getting to be like studying the left hind leg of a flea. If you really need mpg to three decimal places, you just might have OCD. Also, I have been topping off gas tanks in various vehicles for the last umpteen years and never any issues.
@MidCow3 @AM123 - Thank you for your info. I apologize if I sounded on your opposite side. As I mentioned in my previous post, I plan to stop when the fuel pump stops in the future. I appreciate your info and it is new and educational to me as I never knew that vapor canister before.
I watched the YT video, but did not research the CNN reviews - but I am not sure where the opening to the vapor canister is inside the fuel tank. If I were to design it, I would put that opening at the top of the fuel tank - so that overfilling the tank to some extent won't damage much. In the meantime, I do feel lucky if that is the case overfilled tank will damage the vapor canister.
I haven't had my NX350h that long but it seems everytime I fill up the vehicle the range goes down. It started at 515 miles range then 508 miles and now 499 miles last time I filled up. I have been lighter on the gas pedal. Anyone notice this also?
I haven't had my NX350h that long but it seems everytime I fill up the vehicle the range goes down. It started at 515 miles range then 508 miles and now 499 miles last time I filled up. I have been lighter on the gas pedal. Anyone notice this also?
That range doesn’t look meaningful at all. It’s about 16 miles or 3% of total range. Are you filling at the same pump? Just the sensor for where the pump stops could make a difference.
That range doesn’t look meaningful at all. It’s about 16 miles or 3% of total range. Are you filling at the same pump? Just the sensor for where the pump stops could make a difference.
04-13-24, 02:01 PM
Division come on
I am sure that would give you 3 digit accuracy in filling up your gas tank, even if the second shutoff is not consistent based on the variance in gas batches, gasoline viscosity, ambient temperature, gas temperature, pump differences, season variances, slosh factor (even same pump can have different shut=off characteristics), etc. I also assume ( maybe that is a bad phrase) that you have never experienced an automatic shut-off failure; it is disastrous to see your gas tank overflowing and spewing gasoline to the ground.
, what idf Lexus techs had trouble with math and their calculation formula is 1 to 2 to 3 mpg off. Data Analytics is a ***** to understand.
