The machine must be kept operating at its ______.

I am trying to find the ideal word to complete this sentence.

What I am hoping to communicate is that 'the machine' must be kept in "tip-top" (or "perfect") condition in order to ensure it operates at maximum efficiency. I have tried looking for synonyms on words such as "prime", "apex", and "pinnacle", but this was to no avail.

I am almost certain that there is a professional-sounding word that could complete the sentence and communicate the above information in a clean, crisp, & concise manner.

  • 1
    … at its design parameters. … peak performance
    – Jim
    Commented Jan 3, 2022 at 20:42
  • 5
    Needs more context. You could be asking about throughput vs. effort which would describe its most efficient utilization. Or you could be asking about top sustainable speed, or it's top theoretical speed that will almost certainly destroy the machine.
    – Arluin
    Commented Jan 4, 2022 at 17:15
  • 1
    I find this question pretty abstract and hard to understand. It almost feels like a riddle, where you give us a series of cryptic clues and we have to try to guess what you're thinking of. Do you actually have some particular kind of machine in mind? If so, can you please just tell us what kind of machine it is? Commented Jan 4, 2022 at 22:07
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    Woah, in the question you say it must be kept in "tip-top condition" to operate at maximum efficiency, but in a comment above you say it does not "optimise" its use of energy. Can you clarify? Is the word you're looking for more along the lines of "well-maintained" - you want your reader to care for the machine so it can deliver impressive performance? Is the problem you are being indirect - could you say "Maintain the machine well/carefully to ensure optimal performance/efficiency"? Commented Jan 5, 2022 at 6:43
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    Not only am I in doubt that the word you're looking for exists, I doubt that the idea you're trying to express makes any sense. In the Rolls-Royce example, if it were a real engine operated in that fashion, after some time you're going to need to shut it down for maintenance in order to restore it to "tip-top" condition, because operating at full power for an extended period causes wear on the machine.
    – David K
    Commented Jan 6, 2022 at 13:50

7 Answers 7


The first word that occurred to me was optimum. Four major dictionaries suggest that this is a good choice:

Merriam-Webster definition 1 is “the amount or degree of something that is most favorable to some end”.

Cambridge defines it as “best; most likely to bring success or advantage”.

Collins says “The optimum or optimal level or state of something is the best level or state that it could achieve.

Oxford defines it as “Most conducive to a favorable outcome; best.

  • 1
    Optimum could definitely complete the sentence and effectively communicate the information, but for some reason it doesn't feel like the word I'm looking for. Thank you, this answers the question I suppose, but I am still almost certain there is another word which communicates the information in a confident and professional manner. Commented Jan 3, 2022 at 16:27
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    I routinely hear it used in professional contexts; I'm not sure why you feel this is not "confident and professional". Commented Jan 3, 2022 at 16:28
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    Perhaps "powerful" might be a better word than "confident"; if someone or something is operating at its "optimum" it is at its best and operating at maximum efficiency, but it is not (necessarily) powerful. I appreciate I am nit-picking a little bit here and didn't mention this in the initial question, but your answers allowed me to clarify this point. Commented Jan 3, 2022 at 16:30
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    If something is kept in "optimum conditions for XY&Z" for example, it's kind of like saying that in order to be at its best the machine must be kept in a safe bubble which protects it from other factors which would reduce efficiency. The machine should not require shielding though, it should be in its prime and kept operating in its prime - the outside world shouldn't make a difference. Hence the word "powerful". The word that meets this criteria is the word I am after. Commented Jan 3, 2022 at 16:46
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    Actually no. I will not settle for less. I will continue this search by myself. If anyone knows the word I am looking for then please drop it here, if I discover the word myself then I will be sure to let you know. Commented Jan 3, 2022 at 18:15

One common word often used in such contexts that you seem to have overlooked is peak:

constituting the highest or maximum level, volume, etc.; optimal; prime:

a machine running at peak performance.


This word finds frequent usage in the physical world, and so might serve OP's purpose well:

{Physics} the maximum value of a quantity during a specified time interval:

a voltage peak.


Another good choice would be the phrase in full swing.

If something is in full swing, it is operating fully and is no longer in its early stages.

When we returned, the party was in full swing and the dance floor was crowded.


Also this

firing on all cylinders

To be functioning or operating at the most desirable or greatest possible level of efficiency, speed, or productivity.

The automated messaging process is firing on all cylinders now that we've solved the bouncing issue.

I'll be firing on all cylinders after I've had my coffee.

[The Free Dictionary]


I would simply use at its best:

at the highest standard that can be achieved (Cambridge)

I see it is rather commonly used with the verb to operate:

If your brain was a computer, it would take 25 years to write all the code for it to operate at its best. (archives.drugabuse.gov)

Bringing together all parts of the organisation to help the system operate at its best (cipd)

Otherwise, if you need to sound more official, you could use a phrase instead of a single word: operate at its best efficiency point, operate at its utmost capacity, operate at its utmost level of efficiency.

  • The issue I have with this answer is that "at its best" is somewhat vague. The word I am trying to remember would sufficiently communicate that the machine must BOTH be maintained at optimum conditions, AND be operated in the most efficient manner. Commented Jan 3, 2022 at 16:19
  • 2
    @Rukcus975 Now you're changing the question. Originally you said that if the machine was maintained at optimal conditions, that would cause it to be operated in the most efficient manner. According to that, we wouldn't have to specify both parts, because the first part implied the second.
    – David K
    Commented Jan 6, 2022 at 13:42

...'the machine' must be kept in "tip-top" (or "perfect") condition in order to ensure it operates at maximum efficiency.

The machine must be kept operating at its optimum.

optimum (n.)

The optimum or optimal level or state of something is the best level or state that it could achieve. Collins

The most favourable or advantageous condition, value, or amount. (OED)

The procedures covered by this term are carried out periodically to keep the machine running at its optimum. J.T. McGuire; Pumps for Chemical Processing

Adequate amounts of water keep the body hydrated and functioning at its optimum. Michael Sunnarborg; 21 Days to Better Balance: Find More Balance in a Busy World


According to Google ngram viewer you’re probably looking for “kept operating at its maximum capacity”.

The word “maximum” most often follows the word “operating at its” though that doesn’t end the sentence. You need at least one more word, a noun for “maximum” to describe. Of the examples I looked at “capacity” sounds the most natural.

  • I would personally say "at maximum capacity" rather than "at its maximum capacity", but either would work.
    – Hearth
    Commented Jan 5, 2022 at 5:18
  • "at full capacity" sounds more natural to me. Commented Jan 6, 2022 at 7:32

How about, "Kept operating to / at its specifications"?

" A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard.

There are different types of technical or engineering specifications (specs), and the term is used differently in different technical contexts. They often refer to particular documents, and/or particular information within them. The word specification is broadly defined as "to state explicitly or in detail" or "to be specific". "

  • This would benefit from an explanation of how it answers the question.
    – livresque
    Commented Jan 5, 2022 at 1:48
  • +1 This is what first came to my mind (along with "... operating as designed"
    – Papa Poule
    Commented Jan 5, 2022 at 16:23

I apologize for using the answer box for this, since this is really a very long comment and barely an answer at all.

If I understand correctly, you're trying to come up with a phrase describing the recommended maintenance and operating conditions of a machine.

(Am I correct in thinking that you want a word which describes both the maintenance conditions and the operating conditions of the machine? By "maintenance condition" I mean things like "the airplane's oil tank should be topped off and the seat belts should be undamaged," and by "operating condition" I mean things like "the airplane should be flown at a maximum speed of 180 knots and should not be flown in clouds.")

The phrase should have a meaning similar to:

  • in tip-top condition
  • in perfect condition
  • in top physical shape
  • in a flawless state
  • operated in a manner which allows it to achieve its maximum potential
  • powerful
  • looking slick and operating smooth

Is my understanding correct so far?

You also have some kind of "extra fact" in mind, which you've described in two different ways:

  • "the external environment, and external factors, should not be able to interrupt [the machine's] productivity."
  • "The machine should not require shielding [...], it should be in its prime and kept operating in its prime - the outside world shouldn't make a difference."

However, I don't know how this "extra fact" relates to your question. Is this a fact that the phrase you're searching for is supposed to convey? Or is this fact just a piece of information that you're giving us in order to help us answer the question?

I'm particularly confused by your statement that the machine "must be operated in a manner which allows it to achieve its maximum potential" (emphasis added). Are you saying that it's the kind of machine where if it's operated at its maximum potential, then it continues working perfectly, but if it's operated at less than its maximum potential, then that causes it to suffer damage? Or are you saying that the machine is so precious that it must be used for all it's worth, and that failing to achieve its full potential would be a terrible waste?

In any case, I have two suggestions. I'd like to hear whether you think one of these fits or not, and if not, why not:

  • The machine must be kept operating at its utmost full potential.
  • The machine must be kept operating in full flourish.

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