Full tank vs frequent visits to petrol station

Your friend is talking pure waffle

FrankC21 wrote: »

Hi,

One of my mate at work - a big car enthusiast - gave me an advice against puttin €20 each time I go to the petrol station, he said that I should fill up the tank up to the brim. I usually put €20 and when it nearly gone put another €20, I kinda think I will save money this way.

His reason is that if I do not do this, I keep releasing the built up/gas pressure each time I visit the petrol station and that pressure/gas is the actual diesel i paid for, evaporating out into the air.

Is that an actual fact? He recently change his car from 2007 petrol RAV4 AWD to a nissan 1.5 dci deisel and a full tank will last him 2-3weeks.

OP friend is fairly right. First starting and stopping a car uses more fuel. Even the act of pulling into and out of a garage uses fuel. 20 euro's worth is equivalent to about a quarter tank of fuel. That is four fills to every full tank of fuel. OP is starting and stopping a car 4 times instead of once.

Filling a tank is equivalent to carrying a half a tank of fuel with you all the time. A quarter tank is equivalent to carrying an eight of the tank all the time. It's equivalent to carrying an extra 20 kgs around in your car. This will have very little different on fuel economy.

On OP friends point about trapped gas he is correct. If you spill a small bit of petrol on the ground it evaporates. An empty tank will fill with petroleum gas. That why you should never smoke when filling you car with fuel especially petrol.

At best Op you are saving nothing however IMO what you are doing is costing you money

grogi wrote: »

Savings are there (you are not ferrying around weight of the fuel) but it is minimal.

You're however wasting a lot of time getting to the gas station three times as frequently as needed.

Not just time but fuel as well. The physical act of stopping and starting a car uses fuel. And IP friend is right about fuel evaporation when it turns to into a gas especially in hot weather. Why do you think there is such a deal on fuel tanks

Atlantic Dawn wrote: »

There might be some saving if you were driving in an urban area passing multiple fuel stations so no risk of running out and kept tank at 25% full, each litre of fuel is an additional kg weight in the car, savings would be in the single figure €'s over a year.

1 litre of water weighs 1kg, petrol is less dense and weighs around 770g per litre.

Surely the time wasted faffing about in a petrol station and these days being exposed to COVID risks (however minor) mean filling to the brim a no brainer

There is also the risk of dropping an extra €5 on coffee/choc/flowers for the Mr/Mrs (or both). Think of the waistline!

I always fill it up and then let it get near empty,I pass several stations going about my daily business but wtf would you want to be messing around with filthy pumps more than is necessary.

WacoKid wrote: »

I always take the approach:

1. Don't continually run on low fuel as you are dragging the dirt from the bottom of the tank through the system.
2. Let the tank run somewhat low before refueling so you are not keeping old fuel in the tank. Constantly filling up from 1/2 to full means there is fuel there that is never getting burned off, or a least taking a long time to do so.

As you pour the fuel in it'll be mixing with the old fuel and once the car moves then it'll be all mixed together, all fuel is millions of years old.

At the end of the day it's a trade of off saving a few cent by not hauling extra weight in fuel* vs having to spend more time at petrol stations. If your tight for cash and have loads of time stick €20 in, if your tight for time brim it.


* For the majority of people who stick €20 in they'd save more by checking tyre pressure, getting the car serviced and emptying all the crap they have out.

filling your tank to the brim, your literally burning fuel to carry your fuel. if the distance you have to travel to the station is out of your way then thats a different matter based on how far that is. if your passing the station daily then small fill ups are the way to go.

purely from a factual point of you. i dont think the majority care either way

Leonard Hofstadter wrote: »

Life's too short to be spending lots of time at petrol stations re-filling a car all the time. This is one of the reasons I don't like EVs, even the ones with decent range still need at least half an hour to recharge when low on battery.

Aside from that, brimming every time means it's possible to work out exactly what the fuel economy is, so it's much easier to pick up on whether your car has an issue if you know how much fuel you've used since you last filled it up - and the only way to do that accurately is if you fill it every time, note down how many litres were needed to re-fill it and the distance travelled since the last fill up.

Good point about the fuel economy, mine always improves as we move into this time of year.