Greetings everyone, quick question. Is topping off a diesel fuel tank bad? Car is a 15 vw golf tdi. I know topping off is bad for gasses but will it harm my car? I've read that some ppl top off their cars to the filler neck so that they get true mpg ratings for every tank. After the diesel nozzle clicks off I can get a extra 1-1.5 gallon once the foam settles.
Topping off a tdi, bad or good?
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no practical benefit, anyone who thinks so...isnt being logical.
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
Originally Posted By: 01_celica_gt
no practical benefit, anyone who thinks so...isnt being logical.
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
It's an accurate way to track fuel economy, unlike gas, diesel foams a lot so the foam will trigger the nozzle to stop. It's just easier doing it this way because you don't have to worry about other variables. I also usually don't fill up before I park, I do it before my 38 mile commute home from the gas station by my work.
I really only do this to track my fuelly mileage. If it's bad I'll stop.
no practical benefit, anyone who thinks so...isnt being logical.
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
It's an accurate way to track fuel economy, unlike gas, diesel foams a lot so the foam will trigger the nozzle to stop. It's just easier doing it this way because you don't have to worry about other variables. I also usually don't fill up before I park, I do it before my 38 mile commute home from the gas station by my work.
I really only do this to track my fuelly mileage. If it's bad I'll stop.
For a diesel, topping off is OK.
For a gasoline powered engine: Topping off with extra fuel and excess vapors can cause the Fuel Evap System to go bad, tripping a CEL. Going to the same gas station and/or pump will provide an accurate MPG reading that is averaged over multiple fill-ups. No need to top-off after the fuel nozzle stops on its own.
For a gasoline powered engine: Topping off with extra fuel and excess vapors can cause the Fuel Evap System to go bad, tripping a CEL. Going to the same gas station and/or pump will provide an accurate MPG reading that is averaged over multiple fill-ups. No need to top-off after the fuel nozzle stops on its own.
you cannot get a modern tank full anyway, there's always a pocket of air inside the tank. Pretty much like it is with the windscreen washer fluid.
Yep, the Mk4 Golf's TDI tank had an air pocket that would remain even if the tank was filled to the brim. There was a valve that is pushed in by the cap (when it's in place) to vent the air space to the filler neck.
The trick to get more range was to press the valve while filling so that the expansion pocket would fill up.
The tank cap was fully vented to atmosphere, not sure if that's still the case with diesels.
The trick to get more range was to press the valve while filling so that the expansion pocket would fill up.
The tank cap was fully vented to atmosphere, not sure if that's still the case with diesels.
gathermewool
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Would throttling down on the nozzle for the last few gallons help? How about stopping a few gallons before the nozzle typically trips and then topping off at a reduced flow rate?
Originally Posted By: gathermewool
Would throttling down on the nozzle for the last few gallons help? How about stopping a few gallons before the nozzle typically trips and then topping off at a reduced flow rate?
that's how I do it. throttle down after the first click off.
Would throttling down on the nozzle for the last few gallons help? How about stopping a few gallons before the nozzle typically trips and then topping off at a reduced flow rate?
that's how I do it. throttle down after the first click off.
gathermewool
Site Donor 2023
Originally Posted By: Jetronic
Originally Posted By: gathermewool
Would throttling down on the nozzle for the last few gallons help? How about stopping a few gallons before the nozzle typically trips and then topping off at a reduced flow rate?
that's how I do it. throttle down after the first click off.
I meant before it clicks off. When my low-fuel light comes on, I usually fill up with ~ 14.X gallons pretty cinaistently. In this example, I'd throttle down or pause at, say, 13 gallons.
Originally Posted By: gathermewool
Would throttling down on the nozzle for the last few gallons help? How about stopping a few gallons before the nozzle typically trips and then topping off at a reduced flow rate?
that's how I do it. throttle down after the first click off.
I meant before it clicks off. When my low-fuel light comes on, I usually fill up with ~ 14.X gallons pretty cinaistently. In this example, I'd throttle down or pause at, say, 13 gallons.
1 gallon is a lot to pump with reduced flow. the foam is there but dies quickly which is why I let it click off and then pump with reduced flow if I want to get as much as possible in.
Originally Posted By: dothedrew1202
Originally Posted By: 01_celica_gt
no practical benefit, anyone who thinks so...isnt being logical.
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
It's an accurate way to track fuel economy, unlike gas, diesel foams a lot so the foam will trigger the nozzle to stop. It's just easier doing it this way because you don't have to worry about other variables. I also usually don't fill up before I park, I do it before my 38 mile commute home from the gas station by my work.
I really only do this to track my fuelly mileage. If it's bad I'll stop.
if you're tracking your mileage, the error due to the "full tank" will diminish if you just do your statistics over multiple fill-ups rather then one fillup. At the end of your period you'll only be off by the error of the last fillup level-first fillup level.
You know how much you put in the middle over multiple fillups.
On the other hand, topping off everytime potentially spills a little fuel into some overflow or some evap or whatever system your car may have for expansion. So this technique I feel will actually introduce more error into your mileage tracking instead of reducing your error. Plus your goal is to have high MPG, so you're losing out a bit there too (however minimal it maybe).
If the point though is for convenience, and you need that extra gallon so you can drive longer, that's a better reason.
Originally Posted By: 01_celica_gt
no practical benefit, anyone who thinks so...isnt being logical.
Also, the more weight a car has to carry, more stress on the fuel economy, extra gas = extra weight
It's an accurate way to track fuel economy, unlike gas, diesel foams a lot so the foam will trigger the nozzle to stop. It's just easier doing it this way because you don't have to worry about other variables. I also usually don't fill up before I park, I do it before my 38 mile commute home from the gas station by my work.
I really only do this to track my fuelly mileage. If it's bad I'll stop.
if you're tracking your mileage, the error due to the "full tank" will diminish if you just do your statistics over multiple fill-ups rather then one fillup. At the end of your period you'll only be off by the error of the last fillup level-first fillup level.
You know how much you put in the middle over multiple fillups.
On the other hand, topping off everytime potentially spills a little fuel into some overflow or some evap or whatever system your car may have for expansion. So this technique I feel will actually introduce more error into your mileage tracking instead of reducing your error. Plus your goal is to have high MPG, so you're losing out a bit there too (however minimal it maybe).
If the point though is for convenience, and you need that extra gallon so you can drive longer, that's a better reason.
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Originally Posted By: raytseng
if you're tracking your mileage, the error due to the "full tank" will diminish if you just do your statistics over multiple fill-ups rather then one fillup.
this is the point I was trying to make exactly
if you're tracking your mileage, the error due to the "full tank" will diminish if you just do your statistics over multiple fill-ups rather then one fillup.
this is the point I was trying to make exactly
I've always waited till it clicks off then gone and cleaned the windshield and wipers to let the foam settle, then filled till it clicked again and called it good.
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