Owner’s manual
What type of gas does a string trimmer take?
For the Craftsman 316791081 gas line trimmer, we use unleaded gasoline mixed with 2-cycle engine oil at a 40:1 fuel-to-oil ratio. Mix the fuel and oil in a separate approved fuel can, then fill the trimmer’s tank (see the owner's manual).
Fuel type and mix ratio for model 316791081
Use fresh, clean unleaded gas and 2-cycle oil mixed at 40:1.
- Use unleaded gasoline (do not use straight gas in a 2-cycle trimmer)
- Mix 40 parts gas to 1 part 2-cycle oil
- Mix in a separate fuel can, not in the trimmer’s fuel tank
- Use fresh fuel; do not use mixed fuel stored longer than 30 days
- Add fuel outdoors in a clean, well-ventilated area with the engine cool
Quick mixing table (40:1)
| Gas amount | 2-cycle oil to add | Result |
|---|---|---|
| 1 gallon (3.8 L) | 3.2 fl oz (95 ml) | 40:1 mix |
| 1 liter | 25 ml | 40:1 mix |
How to mix and fuel it correctly
- Pour the measured unleaded gas into an approved fuel can.
- Add the correct amount of 2-cycle oil.
- Cap the can and shake to mix thoroughly.
- Let the engine cool, then fill the tank with the mixed fuel.
Why it matters
A correct 40:1 mix protects the 2-cycle engine’s internal parts. Straight gas or the wrong ratio commonly causes hard starting, poor performance, overheating, and premature engine wear.
Last updated: February 2026
How to replace line on Craftsman gas trimmer?
To replace the cutting line on your Craftsman gas trimmer model 316791081, remove the bump knob, pull out the inner reel, then wind new 0.095 in. (2.41 mm) trimmer line onto the reel in tight, even layers (no overlaps) before reassembling the head. See the owner's manual for the exact steps and diagrams.
Before you start (safety and the right line)
- Shut the engine off and let the muffler and cutting head cool.
- Disconnect the spark plug boot to prevent accidental starting.
- Use 0.095 in. (2.41 mm) replacement line (the specified size for this model).
- Never use metal-reinforced line, wire, chain, or rope.
- Clean grass and debris from the cutting head so the reel seats correctly.
Steps to replace the line (rewind the inner reel)
- Hold the outer spool and unscrew the bump knob counterclockwise.
- Remove the inner reel and the spring.
- Clean the inner reel, spring, shaft, and inside of the outer spool; check the indexing teeth for wear.
- Choose your line style:
- Single line: use about 20 ft (6 m) and fold it into two equal lengths.
- SplitLine: use about 10 ft (3 m).
- Feed the line through the reel holes as shown in the manual, then wind in the direction indicated on the reel.
- Wind in tight, even layers; keep the two lines separated so they do not overlap.
- Reinstall the spring, seat the inner reel, then reinstall and tighten the bump knob.
Quick reference: single line vs. SplitLine
| Line setup | Typical length used | Key winding tip |
|---|---|---|
| Single line | ~20 ft (6 m) | Keep two strands separated; do not overlap ends |
| SplitLine | ~10 ft (3 m) | Split back about 6 inches before winding |
Why it matters
Correct line size and winding direction help the head feed line smoothly when you bump. Overlapping wraps or the wrong diameter can cause binding, poor feeding, overheating, or welded line inside the reel.
Last updated: February 2026
What is the gas mix for a string trimmer?
For the Craftsman gas trimmer model 316791081, use a 40:1 fuel mix: unleaded gasoline + 2-cycle oil. Mix the fuel in a separate approved gas can (not in the trimmer’s tank) to protect the engine and keep starting reliable; see the owner's manual.
40:1 mix amounts (quick chart)
Use this table to measure accurately.
| Gasoline amount | 2-cycle oil needed for 40:1 |
|---|---|
| 1 gallon (US) | 3.2 fl oz |
| 1 liter | 25 ml |
How we recommend mixing fuel (best practice)
- Use fresh, unleaded gasoline.
- Use 2-cycle oil designed for air-cooled engines.
- Measure oil first, then add gasoline in a separate fuel can.
- Cap the can and shake to blend thoroughly.
- Fill the trimmer only after the engine is off and cool.
Fuel stabilizer guidance (helps prevent gum and corrosion)
This model’s manual recommends using a fuel additive (stabilizer) mixed into the fuel can.
- Add stabilizer to the fuel can, following the stabilizer label.
- A common dosing reference is 0.8 oz (23 ml) stabilizer per gallon.
- Never pour stabilizer directly into the trimmer’s fuel tank.
Why it matters
A 2-cycle engine depends on the oil in the fuel for lubrication. Running the wrong ratio (too lean on oil, or poorly mixed fuel) can cause hard starting, poor performance, and severe engine damage.
Last updated: February 2026
