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Comment by chrononaut | Hacker News Reader

> ..as I think most people are just filling up to the top instead of half way..

Perhaps I am missing something here, but are you referring to vehicles in this context? Is it not common to always fill your tank to the top?

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Depends a lot on the social status I think. Growing up in a poor household, we never worried about gas prices. When the salary came, we would buy 200HRK worth of petrol and use the car as long as it had petrol. After that, you walk. It was never a full tank and these days its not even half a tank.

I think about myself as a pretty standard middle class person who's obviously empathetic to those who have less. But this proves how easy it is to be out of touch an not even realize it. I really had no idea. I just assumed when you filled, you filled all the way.

Unless your petrol station is on one of your regular routes, it's false economy not to fill up completely when you have an empty tank, otherwise you are incurring an extra trip to the petrol station.

Of course if you can't afford a full tank, and are living hand to mouth each month/week, then you are in the poverty trap where everything is a percentage more expensive for you overall.

But the efficiency is lower driving around with a full tank.

I think not. With a full tank there is less room for fumes to expand. I believe less fuel in the tank means worse fuel economy.

Found this[1] from a quick search.

[1] https://www.carsforsale.com/how-to/5-simple-reasons-to-keep-....

In addition to my sibling comment, I'd point out that the weight of fuel is negligible in this application, especially in a smaller car. A full 14 gallon tank weighs half of an adult male. You'd save more fuel in the long run by losing some weight, but it still wouldn't be that much.

It’s expensive being poor. They also pay more fees for financial products and the like. For example poor people use expensive Western Union and rich people use wire transfer

Found this: https://theconversation.com/can-you-save-money-at-the-bowser...

Very nice calculation. The results were that by filling up two half tanks as opposed to fully topping off one can get an extra 3.5 kms, albeit with a time penalty for going twice to the gas station. Hardly worh it as just making the round trip to the gas station would probably eat up those kms. To this I would add the wear and tear on the car by having it run longer with a nearly empty tank, something which is not recommnded.

Well-off people are usually quick to criticize the decisions of "the poor", but they rarely understand the context. For example, why do poor people stand in line for a new iPhone just to sell it immediately upon exiting the store? Its often because they can get it on a telecom-contract, sell it unopened immediately for less than it usually costs to someone else and pay it off across two years. It effectively serves as a quick cash loan with a moderate interest fee in case you can't get one from a bank and are smart enough not to contact the mob. Every time the iPhone gets more expensive, people with a dire need for cash rejoice...

I know this sounds strange and privileged, but I'd love to see a compilation of tid bits like this (alongside a myth busting element of whether it's really true)

It's not common for people who's budget doesn't allow for a full tank. My family usually just put in a certain amount. 10-20$. When I visit home, I make sure to fill up their tanks in secret and they look at me like I'm insane. "Who fills up a tank?!"

I think for some folks living check to check, it's pretty common to not have enough money for a full fill. In the end it's the same amount of gas, so this seems like just another one of the myriad ways poor people end up spending more resources than wealthier people because they can't invest a bit more now for better returns later.

I always fill up myself because I hate filling up any more than I have to, but when it costs the equivalent of $70 to fill even a tiny car or $140 for a large car, no, it's pretty common to just buy "what you need" for the next few days or whatever.

I'd rather keep my money in fuel than cash, in the off chance hyperinflation strikes, triggering a bank holiday, without me having any physical cash.

But so far this has happened 0 times since I have a car.

That's great if you have the money to spare, but not everyone does.

If you don't have money for fuel, I warmly recommend learning about hypermiling.

The main ideas are not to step on the gas pedal more than say, 30%, and use the smallest car for the job.

Don’t forget coasting. On a modern fuel-injected car there is no fuel injected into the cylinder while coasting.

If you're referring to coasting out of gear then that is incredibly dangerous

May I ask why? The breaks still work out of gear.

If you have money to spare, you're also not going to be able to keep a meaningful share of it contained in filled-up household vehicles, even if you own several of them (such that it'll actually function as a sum large enough to offset hyperinflation in any way that matters).

But, don't forget that evaporation will be greater by maintaining a full tanks.

Besides, you don't want your fuel aging more than 6 or 12 months. So, if you drive less than 40 miles per month (as in a pandemic), it can make sense to just fill up 1/2 way or 3/4.

Still seems odd to me. Whether it's $70 a week or $140 every two weeks the total is the same. Only difference is how many stops you have to make, and maybe a 1% difference to the average weight of the vehicle.

It is odd to you because you have never had to live paycheck to paycheck. Many people are barely getting to the next pay day so that extra $70 the first week means less food that week.

True, if you have literally $0 cash on hand then it could make sense. If you ever get your hands on $70 though that seems like a worthwhile investment to spend ~50% less time at the gas station for the remainder of your life. Probably one of the more cost efficient quality-of-life purchases you could make in my opinion, which is why I find it odd that it's not more common (apparently).

But "time at gas station" is only like 3 mins per visit though. Yes it's not where you want to be but in absolute time terms it isn't much, especially if a gas station is on your typical travel route

Of course it is never quite that simple. When people are cash strapped and under stress, pure unemotional logic may not drive all decisions. Making a $140 purchase when you know you can get by in the short term with a smaller purchase just doesn't add up to a person in that situation.

You aren't addressing the situation the people are in. They are constantly choosing which need to address with the funds they have at present, not simply deferring the purchase of one half tank of gas.

Building a small financial buffer would likely improve their situation a great deal. It seems likely that it isn't always the case that the lack of buffer is a choice...

If you’ve spent your money on gas, you can no longer choose to use it on surprise expenses and forgo driving. Money is more liquid than gas, it turns out.

I've had periods when the kids were small and expenses high when I would put in just enough gas to go till the paycheck came in, or even try not to drive in those gap days. Stressing and unsustainable.

Most people fill in small increments usually relating to their pay point. This is especially so for the UK where weekly pay is popular. I suspect this is a worldwide thing.

I’ve seen some people keep the tank only partially full because it improves performance (the car will be more efficient if it is lighter and might eg handle better too, especially if it is a small car) though I don’t really buy that argument.

But if you supposed that everyone drove normally until their tank was 1/8 full then refuelled to the top, the average tank would be 7/16 full so if lots of people refuel all at once that is 9/16 times a lot of fuel tanks.

That argument seems ridiculous. Gasoline weighs 6.3 pounds per gallon and most cars have 15-20 gallon tanks, so if you keep your tank around half-full your car will be lighter by maybe 50 or 60 pounds. Any performance improvement from that would be imperceptibly small.

Sorry but this is just wrong. The difference in feeling after filling up a small car from empty is significant just for normal driving. Look at what people pay for making sports cars lighter - 50 pounds is a lot!

Even small cars weigh thousands of pounds. Fifty pounds is objectively not a lot. If you're trying to tell me you can tell a significant difference in performance and handling in a car with a 7-year-old in the backseat versus no 7-year-old in the backseat, well, I don't believe you at all.

I can feel that too. Or a suitcase in the back. It's absurd you're telling me I haven't experienced this.

Luckily I don't have to be concerned with what someone who can't notice that believes: it falls to you to explain why there are so many lightweighting products on the market. Why do BMW offer a carbon roof that reduces weight by 5kg? Why did pre-refill-ban F1 only do partial refills? Why do rally co-drivers sit lower than the drivers?

> But if you supposed that everyone drove normally until their tank was 1/8 full then refuelled to the top, the average tank would be 7/16 full so if lots of people refuel all at once that is 9/16 times a lot of fuel tanks.

Sorry, extremely minor nit-pick but I think the fractions go the other way. The average tank should be 9/16 full leading to 7/16 of a tank extra per person.

Yeah you’re right. I should have realised it doesn’t make sense for the numbers to be in that order relative to each other.

> Perhaps I am missing something here, but are you referring to vehicles in this context? Is it not common to always fill your tank to the top?

Depends. When I am in a hurry I buy fuel for an exact amount of cash, so that I can hand over cash and move on.

When I am not, I fill up to the first click[1], and then wait for the attendant to amble on over with a payment terminal so I can use my card.

If I was always paying cash, I would never fill up because I don't really want to hang about while they make change for whatever money I give them. [1] I had a 1986 BMW 525e that, if you filled up to the very top, will leak out excess fuel through an overfill pipe when on a slight (or not so slight) incline. Filling up to the top wasted that fuel.

When gas/petrol shortages occur, it is often because people fill up a 1/2 full tank, rather than waiting for it to be less than 1/4 full. This makes sense if you do not have confidence that you will be able to find gas. But it also means more trips to the station, and a net shift of fuel to automobile tanks.

Keeping extra gas in the tank (aka filling up all the way) is like keeping a savings account - many people can't afford it. Depending on the country, the tank size and the price of gas, you can easily be looking at $100 for a tank vs. just keeping a bit in there to get around.

Tell me you are an American without telling me you are an American.

Jokes apart, in Europe the gasoline is so expensive that you need ~80€ to fill up a small car. For an SUV can be close to 100€.

So we just fill up to just what is absolutely necessary and then we live in anxiety :)

I lived in Europe. Add to that a general lack of cash liquidity of the middle class. I.e. when you're poor you're not sure you might not need those extra euro 60 next week for an unforeseen emergency.

When we lived in Europe in the 90s, my mother would never fill up past a quarter tank.

The european gas pumps even have prespecified fill volumes typically 5,10,20,50€. So when you select the 20€ it will dispense 20€ worth of gasoline.

Many times youth is also splitting gasoline costs for a night out, so everyone will chip in 2-3€ to pour enough gasoline.

Anecdata on this: yesterday I filled up an almost empty 55 Lt tank for €90. The actual petrol cost €35, the remaining €55 was taxes.

No. It's a waste of money. Britain is a small country, you're not going to run out of fuel (ordinarily) on a trip and so it makes sense to keep the money in your pocket instead of turning it into fuel that's sat there doing nothing useful.

Also, it's very common to buy round amounts of value e.g. £30 of petrol, periodically, rather than just fill it up for however much that costs, for some people this makes it easier to think about from a budget point of view.

Also if you fill it up you have to tow it around with you; an extra 40kgs of weight in the car which costs a bit.

The fill it up to the brim meme seems to come from emergency preparedness folks like the police and the army where no vehicle goes to the parking space overnight without being 100% as ready as it can be for tomorrow.

This blew my mind as an American kid visiting England a couple decades ago. I was only ever aware of putting in a credit card and filling up a gas tank all the way, and my uncle took out a 5 or 10 quid note to go pay before filing petrol and he said why should I pay to haul around extra fuel if I pass by the petrol station everyday and I only use half a tank every 2 weeks.

Somebody should do the math of pulling out to the gas station vs. driving with a full tank.

With US engine sizes, fuel efficiency, and number of miles driven, I would guess it makes no difference for most people.

Much fewer proportion of people are driving those peugots or other tiny cars where the weight of fuel would be material relative to the time it would take to fill up fuel more often.

Another British thing that amazed me was their auto insurance prices were based on engine size, and they were fretting about the insurance cost between 2L and 3L cars, and all the vehicles we had in America were 4L+.

No normal person needs a 4l car. You just don't. Heck, 3l is huge and not required with modern engine sizes; between 1 and 2l is plenty for the vast majority of people who are not farmers routinely getting stuck in mud whilst towing heavy equipment.

In 2019, the average new petrol ("gas") car in the UK requires 5.7 l of fuel per 100 km (49.2 mpg) [1].

The corresponding figure for the US is ~9.44 l/100km (24.9 mpg [2,3]).

We really, really need to decarbonise our economy worldwide and in many ways this fuel scare may be the catalyst required, with UK autotrader saying it was driving people to e-car retailers [4].

[1] https://www.gov.uk/government/statistical-data-sets/energy-a...

[2] https://www.iea.org/reports/fuel-consumption-of-cars-and-van...

[3] https://www.epa.gov/automotive-trends/highlights-automotive-...

[4] https://www.theguardian.com/business/live/2021/sep/27/uk-pet...

I know. My neighbor just upgraded from a mini SUV to a 5.7L pickup truck to commute to his office job.

The spoils of a government that does not have a high fossil fuel tax.

4L!? Are you towing an aeroplane?

My most recent car was 1.1L and was fine for anything I used it for...

I do agree that basing insurance on engine capacity is odd though. Why not power to weight ratio or something?

Fuel is/was a lot more expensive in UK.

Yes, that is also a factor I forgot to mention.

>an extra 40kgs of weight in the car which costs a bit.

Do European cars have gigantic fuel tanks?

40kgs is 40 / 0.71kg/L = 56.3L ~= 14.9 gallons.

14.9 gallons is as much, or more than any car I own carries. And I've never put more than 13 gallons into any vehicle ever during a single fill up.

To have that kind of "spare" capacity beyond what would be necessary for my daily commute, I'd need to be driving a large SUV or pickup truck.

I looked up a 3 Series BMW, and they have 40L or 57L tanks in the new models. Down from 60 or so 10 years ago.

I feel like 20kgs is a more accurate number. And that's really the difference between a small woman and a medium sized man driving the same vehicle.

I have a BMW 1 Series and always fill to the brim, highest I've got is 48L so I expect full to be 50L.

Ok 20kg :)

I guess the question is how much does moving 20kg extra cost you over 20k km?

I haven't rounded to the nearest dollar in over 10 years, using credit cards. The only time I cared about rounding was when I paid in cash.

I always fill to the brim, as I value my time more than the incremental value that half a tank of gas will do for me. Obviously it's not the same for everyone.

Unless you value your time at 0, the amount of money you'll save by not carrying around the extra weight is less than the value of the time you'll spend filling up twice.

Yes, but time is not everyone's most precious asset.

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