Stihl FS 91 R Weed Eater: Entry-Level Pro String Trimmer Outdoor Power Equipment Reviews

Stihl FS 91 R Weed Eater: Entry-Level Pro String Trimmer

The Stihl FS 91 R weed eater comes across as a fairly simple string trimmer. But having a basic Stihl weed eater is kind of like having a basic Hitachi framing nailer – there’s still an inherent quality and hidden technology underneath the housing.

A read through the feature list might not impress you, especially if you’re a Pro. It’s a pretty standard list that you’ll find most commercial models share. There’s more to consider than just features, though.

Stihl FS 91 R Weed Eater Engine

Stihl packs a 28.4 cc 4-Mix engine in the FS 91 R. From merely an engine size perspective, it’s right where it needs to be. In Stihl’s professional line, you can go as high as a 36.3 cc engine, though.


The 4-Mix engine on the Stihl FS 91 R weed eater is an intriguing concept. It’s a 4-stroke engine that still requires you to premix your fuel at a 50:1 ratio. Since not having to premix fuel is one of the major benefits of a 4-stroke engine, it seems a bit odd to go the route Stihl does. But there may be some advantages considering that it’s on a Stihl FS 91 R weed eater.

  • Lower weight since there’s no oil pump, sump, or tank
  • No oil system maintenance
  • Fewer emissions just like any 4-stroke engine
  • Lower noise just like any 4-stroke engine
  • Lugging power and high torque

So there’s a balance to strike and you can certainly make the argument that Stihl’s design is a benefit on a string trimmer.

Stihl FS 91 R Weed Eater: Entry-Level Pro String Trimmer

Fuel Capacity

The Stihl FS 91 R weed eater has a 24-ounce fuel tank – large for a string trimmer with this size engine. A full tank will add weight, but you’ll be stopping to refill it less often.


With a dealer recommended price of $339.95, the Stihl FS 91 R weed eater is at the lower end of the price scale in their professional line of string trimmers. You’ll be able to pick it up from a dealer closer the to the $300 mark.

Given that Stihl’s entire range starts at $290 and runs to $580, this model is really an entry-level Pro product in their book.


Performance and Place

How does this Stihl weed eater compare to others currently on the market? For that answer, we turn to our team over at OPE Reviews.  They have a standalone review where the FS 91 R earns a 4.2-star rating out of 5.

Stihl FS 91 R String Trimmer Review

To see how it compares to other popular models, take a look at their shootout, where it finished in 4th place overall.

Best Weedeater Shootout – String Trimmers Gas Powered

Stihl FS 91 R Weed Eater Features

  • Reduced emission engine technology
  • Built in the USA domestic and foreign parts
  • Shoulder strap/carrying system compatible
  • Adjustable front handle
  • Fully lined drive shaft
  • High-tech polymer housing
  • Start/Run/Stop controls on handle
  • Throttle trigger interlock (trigger safety)
  • Air filter cover
  • Protected control cables
  • Heavy-Duty steel-on-steel clutch
  • Protected spark arrestor muffler

Stihl Weedeater FS 91 R Specifications

  • Model: Stihl FS 91 R
  • Fuel: Gasoline
  • Fuel Capacity: 24 oz
  • Engine Displacement: 28.4 cc
  • Weight: 12.1 pounds
  • Warranty: 2 years
  • Price: $299 ($339.95 dealer suggested price)
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We bought this weed eater yesterday it was working beautifully til the cap flew off and went who knows where and the line went crazy and twisted all up in a ball with the weeds all knotted up in it. Now I have no idea where the cap is and if I need to take it back or what