Stihl FS 91 R String Trimmer Review

Stihl FS 91 R
PTR Review
  • Performance 9.0
  • Fuel Efficiency 9.6
  • Ergonomics 7.0
  • Features 9.3
  • Value 8.0

For those who're familiar with the Stihl brand, it probably won't surprise you to learn that the FS 91 R works really, really well. Power and runtimes are on-point. But, you might need a strong back and some hearing protection, because this trimmer is both heavy and loud.

Overall Score 8.6 (out of 10)

While the work doesn’t really slow down at this time of the year in Florida, those of us who review tools for a living had a great opportunity to put 10 of the OPE industry’s best string trimmer models up against each other. We wanted to see which brand offered the best performance, ergonomics, features, runtimes, and value. If that sounds like something you’d be interested in, you can read about the testing procedures and results here.

One of the things we like to do after a shootout is to go back to each individual model we tested and take a closer look at it. Today, we’re taking another gander at our 4th-place finisher, the Stihl FS 91 R String Trimmer. In typical Stihl fashion, this trimmer offers a lot of Pro-level performance and runtime. So, where’s the proverbial chink in the armor here? Let’s take a look at the many things that this piece of equipment does right, and the few things that could use some refinement.


To say that the ergonomics of the Stihl FS 91 R could use a lot of work would be overstating the case by a large margin. The truth is that we’ve got a bit of a mixed bag here. On the one hand, Stihl sinks a lot of effort into designing tools that lawn care Pros keep coming back to, and with good reason. The Stihl lineup has a reputation for comfortability, among other things. And this trimmer feels comfortable enough: it has the rubberized handles, an easy-to-access throttle, and an appropriately long shaft that won’t force too many people to lurch around the yard.

Stihl FS 91 R

On the other hand, Stihl makes some tradeoffs with this model. It has the largest tank of any of the models we tested at 24 oz, but that kind of fuel capacity adds a lot of weight with a full tank of gas. While the trimmer weighs in at 12.1 lbs on an empty tank, practically speaking, you’ll start your day lugging around almost 14 lbs.

Noise is another complaint we had with this model, and it comes as something of a surprise, as Stihl generally handles sound output very well. The FS 91 R measured 106 dB(A) at the ear and 80 dB(A) at 50 ft.  Far and away the loudest model we tested, this string trimmer would benefit from a better muffler. Of course, many pros will throw on ear protection, so this complaint could be a minor one depending on who uses it.

Fuel Efficiency

Referring back to that tradeoff, here’s the good news: 24 oz. of fuel should last you a while. Making fewer trips back to the truck to refuel will ultimately save you time, and consequently, money. And, with a full tank, the Stihl FS 91 R will last for just over an hour before you’ll need to stop to refuel.

Granted, the FS 91 R was not the most fuel-efficient model we tested. An initial efficiency test, whereby we ran 8 oz of fuel through each model, proved that most of our string trimmers could run for longer on the same amount of fuel. The Stihl FS 91 R finished in 7th place here. So, for whatever it’s worth, you’ll have to stop less often for refueling, but you’re not getting the best fuel economy with this model.

It also bears mentioning that, while the Stihl FS 91 R does feature a 4-stroke engine, it still requires premix fuel. We wish this wasn’t the case, but such is life sometimes. Anyway, for our shootout, we used TruFuel 50:1 Premix fuel to keep things running optimally.

Feature Set

Now that we’ve got all the major criticisms out of the way, let’s look at where the Stihl FS 91 R really excels. Stihl has jam-packed this string trimmer full of features. In fact, it finished in joint 1st-place in this department. Some of the more notable features include a serviceable head, a one-piece straight shaft, a toolless filter change system, and a simplified 3-stage startup procedure.

Stihl FS 91 R String Trimmer Features

  • Reduced-emission engine technology
  • Built in the U.S.A.
  • Shoulder strap/carrying system
  • Adjustable front handle
  • Fully-lined drive shaft for less vibration
  • High-tech polymer housing
  • Protected choke knob
  • Start/run/stop controls on handle
  • Throttle trigger interlock
  • Air filter cover
  • Protected control cables
  • Heavy-duty steel-on-steel clutch
  • Protected spark arrestor muffler


Stihl FS 91 R

Performance is where the proverbial rubber meets the road. A feature-rich string trimmer that struggles with actual trimming doesn’t do anyone a whole lot of good. But, we fitted all of our string trimmers with 0.095 Echo Black Diamond Trimmer Line, and then went to town in some of the thickest grass that Florida has to offer: overgrown Bahia.

The Stihl FS 91 R mowed through a 5′ x 5′ square of this tough grass in 13.5 seconds. For comparison, the fastest model we tested accomplished the same feat in just under 11 seconds.

We also ran these trimmers through a thinner, more typical patch of grass. Here, the FS 91 R finished in just under 9 seconds. Our fastest high torque model handled this same task in just under 8 seconds.

Stihl FS 91 R

The differences between most of the models we tested were negligible. That said, in overall performance, the Stihl FS 91 R finished 5th.


As far as value goes, Stihl does some pretty commendable work with this model. Not only does this model offer some of the best features and runtimes we tested, but it also comes with a 2-year limited warranty. At $299, the Stihl FS 91 R retails for less than many of the models we tested. We’re not necessarily used to this with the Stihl brand, as they usually fall more on the expensive end of the pricing spectrum. But, in this case, only the Ryobi and Troy-Bilt models cost less. Ultimately, between its features, performance, warranty, and price point, we feel that the Stihl FS 91 R presents a really solid value.

The Bottom Line

We’re used to Stihl making well-engineered and comfortable lawn tools that a lot of Pros swear by. The FS 91 R will likely fit into that same mold for a lot of folks, but we feel like Stihl threw us a curveball or two with this model. For one thing, it’s a bit heavier and louder than we expected from this brand. And, while the runtime on the FS 91 R is excellent, its actual fuel efficiency is a little bit lackluster.

However, we’re also not necessarily used to seeing Stihl products priced lower than too many of their competitors. It performs as well as we’ve come to expect from the brand, and because of its large tank, the FS 91 R runs for longer than any of its competitors without needing to refuel. Plus, it includes some excellent features, like a serviceable head and an auto-choke.

Ultimately, the Stihl FS 91 R finished our shootout in an overall 4th place, and only by the slimmest of margins. For those guys already working with Stihl products, rest assured that this won’t be the string trimmer that disappoints you. And, for those folks who are looking to work with the brand, the Stihl FS 91 R should show why so many pros stick with Stihl products.

Stihl FS 91 R String Trimmer Specs

  • Displacement: 28.4 cc (1.73 cu. in.)
  • Engine Power: 0.95 kW (1.27 bhp)
  • Weight: 12.1 lbs
  • Fuel Capacity: 24 oz.
  • Power Source: Gas
  • Warranty: 2-Year Limited
  • MSRP: $299

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Duane Allen

I have the fs80r and it is a beast heavy and loud but cuts like no other that I’ve used

Mary Frey

nice tools

Robert Fish

I have one,mine has a padded shoulderstrap so it’s easy to use.

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