My car makes the same almost silent hum at 65 mph left in 3 as it does in D. When driving around town, I leave it in 3. When jumping on the interstate, the only thing that reminds me the car is in the wrong gear, is the tach as thst’s bigger then the “three” on the dash. That’s is exactly what the manufacturer had in mind to remind hard of hearing retirees, " dufuss, you 're in the wrong gear!"
I gave up being perfect long ago.
I use the tachometer in my automatic Accord to remind me to slow down and save gas. I try to keep it under 2200 rpm in 5th gear. I know that slower saves gas in overdrive, but the tach drives the point home.
Dag, I drive the same way. In town, traffic often accalerates then slows then accelerates again. I just leave it in “3” to prevent constantly going back and forth between accelerator and brake pedals. Occasionally I’ll forget and leav it in “3”…and I usually realize after pondering for 5 minutes why the car feels so peppy when I pass on the highway. But I seriously doubt of it hurts the engine one iota. It’s stilll cruizing well within its comfort zone.
Even try to drive a manual, with an on/off switch clutch, smoothly? You simply can’t just let the clutch out smoothly. You have to rev match. A tach is a nice thing to glance
I drove countless manuals for over 40 years, all smoothly. And all without tachs. Although in the interest of full disclosure I should point out that I did wear out the original clutch in my '89 Toyota pickup…after 295,000 miles. Well, actually, it wore out after I’d taught two kids to drive on ti and given it to my daughter…but it probably would have worn out anyway.
I’ll agree it is probably one of the least useful gauges but what’s it cost maybe $5 or $10 to put in and give the car a sportier dash? I certainly don’t use it for shifting or anything else but I do monitor it on the road to make sure the trans is operating properly. When I bought my 74 Olds, I had to special order the gauges for it for $35. That included the temp, ammeter, and oil pressure gauge but no tack, which I found far more useful. I want temp first, then ammeter, then oil pressure, then a tach but I’ll take what I can get and don’t want to give any of them back.
I drove countless manuals for over 40 years, all smoothly. And all without tachs.
I had 3 vehicles that had tachs…and I basically ignored them. Not needed one bit. When I learned how to drive a stick…I was taught to shift by speed. Unless the clutch is slipping it’s a good way to learn.
When I taught my oldest two kids to drive my Pathfinder with a 5-speed manual…I could tell without looking that they didn’t shift into 5th on the highway. It doesn’t take long to get use to a vehicle and it’s sounds. If you stop paying attention to the tach you’ll start to notice the other signs that I think are more important.
It’s not only about when to shift, how to shift is equally important. Shifting into first at over 15 without a tach is a little like shooting in the dark. I’ve done it a few times and mismatched rev in first gear was quite noticeable. Having a tach makes rev matching much easier.
I’ll agree that tachs are good to have on a car with a manual transmission (even though my first 8 years of manual tranny driving did fine without). But on ATs they’re a decoration 99% of the time.
The only time I actually use a tachometer is while racing, and I don’t race automatic transmission cars. In a street car, it is only to keep you from slapping the rev limiter (VERY annoying!) in a manual transmission car. Actually, that’s the same reason I use it in the race car except replace “annoying” with “slow”.
I use the tachometer every time I use low range on my truck to keep from over revving which can easily occur, especially when you don’t use it on a regular basis.
When a good friend stopped by with his 2013 Miata couple of weeks ago and ask me to drive it, I ask him straight out. " What rpms do you wnt to keep the car under.? " he told me he general keeps it under 4 k for non aggressive driving . After monitoring the gauge for a few moments, you quickly get acclimated to that limit by sound and feel. But, the tachometer made the process much easier and there was no guessing on my part on a car I was not familiar with.
The same when my boss asked me to keep the diesel in his dump truck I was making deliveries in, under 3500 rpms when engine braking. Again, after a while, it was natural but the learning curve is steeper with a tachometer, and the same is true for any unfamiliar car as well when you operate a transmission.
Unless you do the math or memorize speeds from your manual, with out a tach it’s always a guess what rpm you are at and where you should be.
Those of you who breath engine fumes, bleed mobile 1 and slick your hair with wheel bearing grease know intuitively whether you are over revving or not on any car. We mortals need a tach.
Who is proposing that someone constantly stare at any gauge? You glance at them occassionally to see if anything is amiss. Some more often than others. Once you know what you’re doing (getting there may be problematic if you have to LEARN without benefit of a gauge) most gauges are somewhat unnecessary. MOST people are not experts.
I have a motorcycle that can go 70 in 4th and feels no different than it does in 5th. Been caught a few times running 20 miles in 4th and I’ve been riding bikes for 40+years. Glance down and notice tach is running higher than expected, oops, shift. Another bike I have with similar performance has only a speedometer. Sometimes, I find myself checking if I’m in top gear or not because I cannot tell w/o a gauge.
Having a tach has helped me diagnose problems before they became big deals. Why is it running 2000 rpm in this situation? Should be more like 1800…
Unless you do the math or memorize speeds from your manual, with out a tach it's always a guess what rpm you are at and where you should be.
And as I said…the shift points vary depending on load and terrain. So I don’t know how a tach can possibly help you when trying to determine when to shift - Unless you always drive alone and on level ground. Let’s say that when driving on level ground…the optimum shift point from 1st to 2nd is 2000rpms. If use that shift point going up hill you may find the engine sputtering like crazy because it can’t handle that grade in that gear at that rpm.
When I towed my popup with my 1990 5-speed manual Pathfinder…the rpms for my shifting was greatly increased. Almost 1000 rpms. My 98 pathfinder…it wasn’t that dramatic…the 3.3l V6 had significantly more torque and rpm then the 1990 3.0L. My 73 Vega…I noticed a big difference in shift points with just 2 other people in the car. And going up hill with 3 people…forget about shifting into 4th…Had to stay in 3rd at 3k rpm’s.
Sports cars put the tachometer front and center even though speed is what the driver mostly needs to monitor.
Dunno if they still do it, but the Mini has it’s speedo in the center of the dash, and the tach is seated just behind the steering wheel, in plain sight for the driver
You need either wn RPM guage…or an exhaust you can actually hear…if you’re gonna float gears on a stick.
Don’t intend on doing that? Well, neither did I…until my clutch master and clutch pedal went their seperate ways while I was driving.
Dusting off a dormant skill beat the hell out of a tow!
A tach with a CVT is almost more important that with a multi speed shifting transmission.
( my tone deaf wife drives an 06 Escape hybrid , she doesn’t HEAR much difference in the engine, except for extremes, so to SEE it is imperative )
With a CVT you can easily have a wide variance in rpm with a simple lift of the big toe or not.
At any given same mph the CVT will ease back the rpm or increase depending on YOUR intended effort. IF you’ve reach your intended cruising speed then , purposely, let up just a tad on the accelerator effort and you WILL notice a marked drop in rpm as the CVT adjusts.
WITH a tach there to show you this, you can actively participate in you maximum mpg.
WITH a tach for your CVT you can easily tell that …durring acceleation…if you’d let up just a tad and accelerate less rapidly, you save tremendously using much less rpms to do so.
Agree that tachs aren’t really needed in most cases, but they’re nice to have. To stay on the thread topic, I’ll tell my own experiences with my '07 Compass (2.4L, CVT FWD):
Without the tach, I never would have had a clue what rpm I was doing in day-to-day driving without first knowing what the engine sounded like at different rpms. In a car that is new to me, there is no other way to know. I find the tach useful for fuel economy - from a red light I really have to squeeze the pedal lightly to keep it revving past 2000 rpm. The tach lets me cringe at the higher revs anytime I actually want to get somewhere in a decent amount of time.
I just went on a 4 day road trip with my wife and kid. The car wasn’t very loaded down, just two adults, a 4 year old, a couple bags and tent camping supplies, and my bike hanging off the back. Went driving from Vancouver across BC to the Kooteneys, in the Rocky Mountains. My wife was driving at highway speed (70mph +/-) up the steepest part of the Coquihalla highway (a steep mountain pass highway, complete with snow sheds) when the engine broke - must have spun a bearing or something - and the oil light immediately came on. The rod knock apparently made the computer try to put it into limp mode, which made the transmission gear down even further than it already was. We were doing 4000 rpm and it suddenly shot up to 6000 rpm (red line) even though the car was slowing down. This car doesn’t see 4000 rpm in day-to-day use and I probably would have freaked out from the noise it made if the tach hadn’t told me that it was only 2/3 of the red line. (The consensus over here is that the engine speed in this case had nothing to do with the engine breaking down, except that it exposed whatever underlying condition it had) What’s the point of all this? I like having the tach.
Years ago, and don’t ask me which car, the vehicle had dots of three different colrs( or two) spaced through out the speedometer dial to show you where a reference rpm was for each gear. Of course, that wasn’t the best idea as trying to find the dots while driving is akin to texting. Car motors are getting smoother and more difficult to monitor especially in light of lack manual driving experience, so tachometers in automatics to keep economy in mind seem worth while. The little green lights that glow when you drive economically are akin to the idiot lights for tachs like those used to replace temp gauge and charging meter. Again, most owners manuals will tell you what they expect of the driver in using a tachometer for most efficient motor use. I have always looked at them as an education experience which become less needed as you become more familiar with the car. But, as @macfisto points out, they can be an important monitoring tool for problems .
I pay as much attention to the tachometer as I do the speedometer. The tach can serve as an indicator of looming problems related to shift points and what RPMs are normal for certain speeds.
Yeah, OK4450, I don’t pay that much attention to my speedo either. 
Seriously, I glance at mine, as I do the speedo, but for all those years when I didn’t have one I always managed to pick up on signs of an impending issue anyway.