General Question

hsrch's avatar

Why does the auto industry think that tachometers are necessary in passenger cars?

Asked by hsrch (576points) December 10th, 2015

I’m an old guy and have been driving since 1948 or so. Back in the 70’s or 80’s automobile manufacturers began putting tachometers on cars. I’m not sure why there was a demand for this instrument but it doesn’t seem particularly valuable to me. The display on my current 2013 vehicle is as large as the speedometer and takes up quite a bit of space on the dash. I can look at it to see if the engine is running, of course. I see that my car idles at ±700rpm and I suppose that’s of some value. Perhaps someone can enlighten me on the reason for the demand.

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21 Answers

ragingloli's avatar

So you know when to shift up?

LuckyGuy's avatar

For 99 44/100% of the time the driver does not need to look at it.
But…. See that red zone all the way to the right? If you do something boneheaded like leave your automatic in low and then drive out on the highway the tach will indicate to you that you’re doing something wrong. (It will also be your fault when the engine breaks. You were warned!)
In reality there is a top speed limiter to protect the engine. Unlike the old days, most modern cars cannot be destroyed by putting a brick on the pedal.
Don’t try this at home. .

CWOTUS's avatar

I use it (admittedly, not frequently) when driving at speed in hilly terrain. I normally use cruise control for all highway driving except in the aforementioned hilly or mountainous terrain (or when road conditions warrant direct driver control, such as in wet and freezing conditions, snow of any depth, and heavy rain). When I see the tach needle approaching the shift point (which is also a matter of “the feel of the vehicle” and sound, if you can hear the engine starting to labor), then I will usually kick off the cruise and guide the car manually to avoid an unnecessary downshift to maintain speed.

You’re right that most drivers can drive a lifetime and not even glance at the tach, but for some of us, “enthusiasts” and regular drivers alike, it does serve a sometimes useful purpose.

Cruiser's avatar

Most all manual shift transmission cars will come with tachs. My ‘14 car is automatic but has paddle shifters and came with a tach so when I am in sport mode I can visually reference my shift points.

funkdaddy's avatar

I use the tach every single time I’m in the car, please don’t take it.

When starting, your tach will tell you when the car is warm and if everything is running like it should, right away.

When you’re driving
– it’s the best way to tell what gear you should be in.
– gives you a better idea of your fuel economy than anything else available

Pretty much everything else displayed on the dash is interpreted information, the tach gives you something direct and reliable.

JLeslie's avatar

On an automatic car it isn’t necessary, except I guess, if your car is idling high you can see how high.

I have a couple of manual shift cars, and I look at the tach quite a bit.

ARE_you_kidding_me's avatar

I have always driven straight shift, a tach is mandatory and I use it more than the speedo. Same goes for my motorcycles

kritiper's avatar

A tachometer is like fancy wheels on the car: They serve the male ego. It looks good. It’s cool. But serves no real purpose.

ARE_you_kidding_me's avatar

@kritiper “They serve the male ego” in what way? Like compensating for a small dick with a big ass truck? One of my motorcycles only has a tach. I can sort of drive a stick by feel and sound but I honestly look at the tach more than the speedo. Automatic…no real purpose.

kritiper's avatar

@ARE_you_kidding_me That is precisely my point. It doesn’t attract girls.

JLeslie's avatar

I definitely agree it is a male ego thing on an automatic, and an aesthetic thing.

jca's avatar

When I drive standard shift, I don’t use speedometer or tachometer, I go by how it feels.

JLeslie's avatar

I use the tach when I’m trying to decide whether to stay in 5th or shift to 6th. It’s right around when I’m cruising at 50–55 MPH. I do it almost every day on the main street near my house, and yet every day I grapple with whether to shift or not. Lol.

gondwanalon's avatar

My 2007 Ford Ranger has a large tachometer. It may be helpful for a beginner driver or a professional racer but it is useless to me. I know when to shift by truck speed and engine sound. I’d much rather have an oil pressure gage in place of the tachometer.

Hypocrisy_Central's avatar

It is pretty useless on an automatic, if you are not driving a stick it has little value other than making one believe their car is more high-powered than it is.

Stinley's avatar

Does everyone call it a tachometer? In the UK we call it a rev counter
I used to have a Citroen Xsara Picasso that didn’t have a rev counter. I missed it a little but mainly I use the sound of the engine to know when to change gear. I do look at it sometimes now in my current car. But I don’t really know what purpose the knowledge serves

JLeslie's avatar

@Stinley In America I have never heard it called a rev counter, but we do use the word rev to describe a car at high revs. Like telling someone to “rev the car up” in lieu of saying “give it some gas” while in neutral.

jca's avatar

Hahaha when I was writing my answer above, I was going to write that I don’t shift until the car revs.

JLeslie's avatar

@jca I was going to write that we usually use it when describing the sound. That we notice the sound of the high rev, and that’s when we use the term.

jca's avatar

Vroom, vroom!

Stinley's avatar

Looking at both terns, I think they both use the same words just in different languages (English and Greek/ Latin). It’s not like us Brits to be plainer spoken!

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