James Moylan, Engineer Behind Arrow Signaling Which Side to Refuel a Car, Dies
Key topics
The passing of James Moylan, the engineer behind the clever fuel gauge arrow that indicates which side of the car the fuel tank is on, has sparked a nostalgic and informative discussion. As commenters dug into Moylan's legacy, they unearthed other automotive innovations named after their creators, such as the Monroney sticker and Mansfield bars, revealing a fascinating history of design and safety features. Many shared their own "aha" moments, admitting they'd never realized the arrow's purpose until now, while others chimed in with stories of cars where the arrow was misleading or incorrect. This thread is a delightful blend of automotive trivia, design appreciation, and the joy of learning something new.
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- 01Story posted
Dec 26, 2025 at 8:23 PM EST
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https://en.wikipedia.org/wiki/Fuel_gauge#Moylan_arrow
https://www.vermeulenfh.com/m/obituaries/james-moylan-2/Memo...
https://en.wikipedia.org/wiki/Monroney_sticker
Also known as the "Window Sticker"
https://www.getgordon.com/faqs/what-is-mansfield-bar/
I found out around age 35, I think. From reading it online. I’ve told a bunch of people who didn’t know.
There's even a Snopes entry:
https://www.snopes.com/fact-check/fuel-icon-foolery/
Moylan basically added a modifier icon for clarity.
I've driven 2 models of an Italian brand, my previous car had the gas tank on the passenger side, and my current one has it on the driver side. I do wonder why they changed it.
There's also the issue of pulling to a small road side petrol station, having the fuel door on the passenger side means you don't have to be standing next to the busy road while refuelling.
Depending on model years, it could have something to do with Fiat merging with Chrysler in 2014. European brands usually have them on the passenger's side, while US brands have them on the driver's side. Maybe that new Fiat was designed in the US.
The fuel side indicator is quite helpful to me.
[0] https://fordauthority.com/2020/08/ford-designer-credited-for...
I don't ever recall the arrow being paid attention to until listicles and other blog spam were born. It has all the elements of great clickbait.
The design I used to find confusing was the controls for periodic windshield wipers: does the width the triangle indicator represent frequency or period? I eventually just managed to memorize that it means frequency because you get more wiping as you turn it “up”. I don’t think anyone else ever found this ambiguous; we all have our little intuition gaps, I guess.
You don't pull up next to Paris, but I would get a chuckle if the icon had a little Eiffel tower instead of a gas pump.
The fact that it is consistent across vehicles sort of mitigates the problems with it. "Arrow points at fuel door" is not actually hard to remember.
Im not a regular car user, if at all Im renting - but the last 10 times(?) it was always just on the side of the driving seat
Might just be a coincidence
That would mean designing two separate entire fuel tank placements, fuel lines, etc for cars that are available both in left- and right-hand drive variants, with different SKUs for each of the parts needed. There is no way a car manufacturer would do that.
Just think how many billions of times someone has avoided pulling up to the wrong side of the pump because of this arrow - literal lifetimes of effort saved.
And Apple Needs more, for putting power buttons and key ports at that back.
Which way up it should go.
It seems so unlikely that I’ve just searched it to see if it’s possible, but am getting no hits.
Very asymmetric, impossible to plug in backwards, only one possible orientation.
Still absolutely fucking awful. Same for HDMI, displayport.
The RJ series are the only asymmetric connectors I've use that you can easily get in blind.
I’m surprised how tolerable people seemed to find Apples rear ports.
USB.
I used iMacs, mini and pro machines. Any ports in the front would be nice.
My mini does have some front ports. It’s less of an issue with usb-c but the iMac presumably still rear mounts them.
So does the Mac mini.
So does the Mac Pro (well technically they're on the top).
So your complaint is essentially about the extremely minimalist, consumer-oriented iMac.
Ok. Don't buy an iMac then.
When you plug in a USB stick, surely you want it on the front? Do you get around this with an adaptor or something? My use case seems common.
It's been clear that usb-c is the future for a decade now. How on earth do you still have flash drives that are usb-a only?
I probably use the power button once a month, and I'd say this is the norm for most developers/similar people. It's no harder than accessing the menu button/toggle stick on the back of my dell display.
To make it worse, the machines I use have several USB-A ports and at most, 1 USB-C.
This is primary on MRI scanners, for getting files in and off them. We live in a deeply flawed world.
If it's really a significant problem, use the benefits of usb and put a hub or usb extension cord on the desk to connect to.
I just cannot fathom how such trivial factors are a problem for people.
I also don't know anything about any "arrow" signalling anything in my dashboard, maybe it's only on the US-made cars, I wouldn't know cause I generally know on which side I have to fuel my car.
We never, ever use "gasoline" or the Germanic "benzene" for this. Benzene is a specific chemical here.
(I only drive my normal passenger cars, not trucks.)
But I'm me not in the habit of doing that, because it doesn't usually matter for me.
but if you want a more dramatic example, it's right there in the text: Moylan got soaked because of this inconvenience. if he'd gotten a pneumonia as a result of this and died, then that is suddenly much more than a minor inconvenience.
Since learning that, I have the confidence to stick it in first time rather than 3rd or 4th.
That's not to say that USB-C isn't a huge improvement that has thankfully resolved having to know that.
Oh wait.
>On a 1978 Buick Riviera, the gas cap is hidden behind a flip-down license plate on the rear bumper.
The fuel filler door is on the left side (driver’s side) of the vehicle. Therefore, the little arrow on the dash fuel gauge should point to the left to indicate that.
(Most Buick Rivieras of that era had the fuel filler on the driver’s side, though official Buick manuals or build sheets from 1978 confirm this location.)
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Share the links, people!
Usually, if it's Japanese or British the cap is on the left, otherwise it is on the right. Doesn't work all the time, but good enough to be a useful rule.
My Forester is likely to be an exception rather than the rule, however I do feel that the everyday person isn’t going to make the connection between the country of origin and filler side, especially so if it’s not consistent.
I never noticed the Moylan Arrow on my Forester for a year in owning it, and often mixed up the side for that time. Interestingly, my 323 doesn’t have the Moylan Arrow, but the Ford Laser equivalent does.
Although, I believe the platform was primarily developed by Mazda so perhaps they didn’t catch onto this arrow until well after my generation of 323 was on the market.
[1] https://d3nevzfk7ii3be.cloudfront.net/igi/cBUPxJJlgjs6KOI2.f... [2] https://i.ebayimg.com/images/g/Kv4AAOSwt-pjJtKG/s-l500.jpg
You imply they ever had a choice.
Companies like Tesla and Rivian pioneered the trend of bringing webshit-as-an-instrument cluster to the mainstream. Everyone else rode the coattails and immediately copied it.
What is a customer supposed to do? Buy a Mitsubishi Mirage? Build their own instrument cluster?
I see no reason to buy new instead of used, and I see no reason why I would change my car to a newer one anytime soon.
I agree that automotive engineers do not work for the end customer leading to shittier cars, but I also think that most people are unable to vote with their wallet (or just don't care).
I've since met many adults who were unaware of this trick. It's like the real-world analog of an insufficiently discoverable UI functionality.
https://archive.ph/pluwT
https://www.jalopnik.com/2061179/inventor-little-arrow-what-...
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