Home » The Way These Oil Pressure Gauges Are Labeled Seems Bonkers

The Way These Oil Pressure Gauges Are Labeled Seems Bonkers

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I’m interested in the way our cars communicate with us. I think that’s why I’m so interested in indicators and taillights, and on the inside of cars, gauges. Gauges are especially interesting because while taillights and turn signals are how we use the car to communicate to other drivers, gauges tell us information directly from the car. No puppeteering involved, those little moving needles or digital digits are your car’s bits talking right to you. The way we choose to frame the information on gauges is interesting, too – I’ve explored it for fuel gauges a couple times, but today I was introduced to a really strange labeling convention for oil pressure gauges, and I needed to show all of you, stat. So, put your dropcloth down just in case this shocks any fluids out of you.

I was alerted to this by a reader named Nick who saw this interesting Reddit post, which showed an oil pressure gauge (in what I think is an old Alfa Romeo or maybe Fiat) that looked like this:


Do you see what’s going on there? Oil pressure is measured in terms of a unit of force per a given surface area. That’s because the oil in your engine is under pressure, which helps to force it through all those channels and the pressure helps the oil get between all of those spinning metal parts, forming a sort of fluid bearing so the metal bits can’t rub up against one another, in much the same way you or I are encouraged not to rub up against one another in, say, the checkout line at Target.

For most of our readers, the most common units used to measure oil pressure are pounds per square inch, commonly abbreviated as PSI. There are other ways to measure it, too, if square inches are just too Imperial for your Metric mind, like in Pascals (one newton of force per square meter) or as bar (which is 100 kilopascals).


But, let’s get back to our weird gauge here. It’s a gauge that measures in PSI, but instead of being labeled PSI like almost every other oil pressure gauge I can think of is, it’s instead labeled with this ridiculous rebus:


What, and I mean this earnestly, the fuck.

It may take you a moment, but I’m sure you see what they’re going for here: lb is the abbreviation for pound, the slash connotes the idea of “per,” then there’s a literal square, and then the ” which is the abbreviation for inch.

Is this just some weird Italian nonsense, since that gauge is a Veglia Borletti? I checked and, no, we can’t blame this on Italy, because it shows up in other company’s gauges, including Smiths and Jaeger, for example:


So, this seems to be A Thing, and looks like it’s shown up on a variety of cars over the years, from Alfas to Jags to Fiats to whatevers. I don’t understand why this would ever be considered preferable to PSI.

For one thing, it’s just harder to read. That reads like letter O or a zero, since plenty of typefaces square off letters like that. Then, the use of ” for inch is well enough known, but it’s a tiny symbol, and it can also mean seconds as in how you can break down degrees into minutes and seconds. I don’t know why you’d think this was talking about degrees on such a gauge, but I can easily see looking at it and reading “pounds per zero inches?”

Also, conceptually, it’s just feels wrong. It shows a literal square before the inches, like an object unto itself, when, really the “square” being implied is more of a mathematical square, a unit of area, one inch per side. And, yes, while that is a literal square shape, it just, I don’t know, doesn’t read like it should.

I think even using an exponent to denote square would be better, like

lb/” ² or lb/in ²

But even that isn’t great, if we’re honest. None of these are better than the simple PSI, which even takes up less room than lb/▢” anyway.

Does anyone prefer this? I suppose it has some aesthetic appeal, and if I had a car with this on a gauge you know I’d be all over it, showing it off to any poor bastard unfortunate enough to get within ten feet of me and my car.

You know what? Let’s a do a poll! I’m curious if there’s anyone out there who things the goofy letters-and-square-and-slashes-and-hashmarks bullshit is better than PSI, and if you do, I’d love to know why, so tell me in the comments after you vote!




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67 Responses

  1. I totally agree re: “ridiculous” and “wtf” and all that.
    But for the poll I voted A, ‘ cause there’s just not enough *delightful* absurdity in my life — and that PSI alternative notation is grapho-phonetically, hieroglyphically, parallel-universally delightful!

  2. I’d really like to know what John Davis of Motorweek thinks of this weird PSI symbol, given his affinity for gauges. Come on, Jason. Get him on the blower and do some REAL investigative journalism.

    What would make this better is if the metric version was just a “|” or “_”

    You know….for bar.

    …………jokes are funnier when you have to explain them………..

  3. Started to think about using international symbols on all gauges and realized most would be very difficult. You almost have to commit to some country’s unit of measure and maybe put 2 units on the scale. Quantities are easy with 0 to 1 and fractions or empty circles/half full circles/full circles, but that doesn’t work with other gauges.
    We could be getting into developing new international symbols here.

  4. I’m more angry that VDO sells a “kPa x 100” gauge and a “Bar” gauge, I wonder to they sell speedometers marked in “MPH” and “MPHx1.609”?

  5. Oh, speaking of initially confusing gauges, does anyone get confused, at least briefly, when driving a car with identically sized speedometers & tachometers where the tach is calibrated x100 rather than x1000 so both gauges have identical numbers? So 30 on the x100 tach is 3000 rpm whereas the x1000 tach will simply have a 3 which seems clearer & less likely to be confused with the speedometer with its double digits (well, until one hits 100 mph.) Why would anyone want x100? Is there a legit need for such a convention? The x100 tach seems particularly prevalent amongst modern cars & seems especially typical of German cars, at least in my relatively limited experience, though I do have a lovely VDO tach from a Porsche 356 that is calibrated for x1000 UPM (in green with a red trapezoid behind the “6.”) And I’ve seen tachs calibrated x1 on brass era cars which does make for a rather crowded field to read with all those digits, especially the zeros, so it makes sense to increase the multiplication for a cleaner design & for clarity (though the x1 tachs can indeed be easier to comprehend more readily, perhaps ironically.) That said, it doesn’t make sense for the x100 to be seemingly the most common multiple. Yeah, a deep dive on tachometers & calibrations thereof would be informative & greatly appreciated…

    1. Back in High School, my parents had an ’86 Escort wagon 5-speed that I drove all the time. I eventually wanted to get my own car and test drove a Dodge Daytona that I had fancied. So my buddy and the sales rep piled into the car and took it for spin. On a small, two-lane road near the dealership, I struggled to get the car to get up to the 45mph speed limit. After getting back to the dealership, I realized that a) the tach was x100, and b) the tach and speedometer were flipped compared to the gauges in the Escort and I had been checking the tach. To this day, I have no idea how fast I actually had that car going, but my friend said that the sales rep in the passenger seat seemed awfully uncomfortable during the test drive…

  6. Hey, it’s always nice to have a little levity in automotive gauges! And, usually, if one is initially confused by the square looking like a zero or the letter “O” a moment’s inspection will show the “B” in “lb” (and also the “S” in “lbs”) to be rounded so it’d follow that a zero or the letter “O” would be similarly rounded whereupon it becomes obvious that the symbol is indeed a square. Yes, I daresay we all could stand to have the random rebus in our everyday lives.

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