Owner’s manual
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Should I use 87 or 91 gas for lawn mower?
For the Craftsman 917378490 gas walk-behind lawn mower, we recommend using fresh 87-octane unleaded gasoline for normal operation. Higher octane (like 91) does not add power in small mower engines; fuel freshness and proper storage matter more. For model-specific fuel guidance, follow the 917378490 owner's manual.
What to use (and what to avoid)
- Use 87 octane unleaded gasoline (regular).
- Use fresh fuel; stale fuel is a common no-start cause.
- Avoid leaving fuel sitting in the tank for 30 days or longer without storage prep.
- Avoid fuel that has absorbed moisture; it can lead to fuel separation and acids during storage.
- Do not pour engine or carburetor cleaner products into the fuel tank.
Fresh fuel and storage rules (most important)
The manual warns that alcohol-blended fuels can attract moisture during storage, which can damage the fuel system. If you will store the mower for 30 days or longer, empty the fuel system.
Storage steps we use and recommend:
- Empty the gas tank.
- Start the engine and let it run until the fuel lines and carburetor are empty.
- Refill with fresh fuel next season.
Quick comparison: 87 vs 91 for a mower
| Fuel choice | What you get | Best use case |
|---|---|---|
| 87 octane (regular) | Correct everyday fuel for most walk-behind mowers | Normal mowing and weekly use |
| 91 octane (premium) | No performance benefit in typical mower engines | Only if required by the engine label/manual |
Why it matters
Most “fuel problems” on walk-behind mowers come from stale fuel, water contamination, or storage issues, not octane rating. Using fresh gasoline and storing it correctly helps prevent hard starting, rough running, and carburetor problems.
Last updated: January 2026
What year is my Craftsman mower serial number lookup?
For a Craftsman walk-behind mower like model 917378490, the model number does not contain the year. The build year is typically determined from the engine’s model/type/code (often stamped on the engine) or from the mower’s product label; use the 917378490 owner's manual to find the label locations and identification details.
How to find the year (fastest methods)
- Check the engine code first: Most walk-behind mowers use an engine date code that can be decoded into a manufacturing date.
- Look for the mower product label: Common locations include the rear of the deck, under the rear flap, or near the handle mounting area.
- Write down all ID fields: Model number, serial number, and any product number.
- Match the engine and mower IDs: The mower deck and engine can be from different dates if the engine was replaced.
- Use the parts list diagrams: They help confirm you are reading the correct label and assemblies for 917378490.
Serial number formats: what to expect
Many Craftsman mowers do not use a universal “MMDDYY” serial format across all years and manufacturers. If you see a 6-digit number that looks like a date, treat it as a clue, then confirm it against the engine code.
| What you found | What it usually means | What to do next |
|---|---|---|
| Engine “model/type/code” | Engine build date is encoded | Decode the engine code to get month/day/year |
| Mower serial/product label | Mower production tracking | Use it to confirm the correct parts breakdown |
| Only the model number 917378490 | Identifies the mower design | Use it to look up parts and diagrams |
Why it matters
The correct year (or engine build date) helps you choose the right maintenance parts and drive components, especially for items that change by production run like the drive system and blade hardware.
If you are troubleshooting drive issues while you are identifying the mower, the lawn mower wont move troubleshooting video motion drive failure is a good next step; the drive belt and control parts are common wear items.
Last updated: January 2026
Where is Craftsman's model number?
On the Craftsman gas walk-behind lawn mower model 917378490, the model number is printed in the documentation and used on the parts diagrams as “MODEL NUMBER 917.378490”. For the most reliable match when ordering parts, use the mower’s model number (917378490) rather than an engine-only number.
Where to look on the mower
We recommend checking these common ID locations on Craftsman walk-behind mowers:
- Rear of the deck near the discharge opening or rear door
- Top of the deck near the engine mounting area
- Handle support area (near the lower handle brackets)
- Under the grass bagger frame area (if equipped)
- Any product label plate riveted to the deck
If the label is worn, use the illustrated parts breakdown in the 917378490 owner's manual to confirm you are selecting the correct assemblies.
Mower model number vs. engine model number
Many customers find an engine ID and assume it is the mower model. They are different.
| What you’re identifying | What it’s used for | Example for this mower |
|---|---|---|
| Mower model number | Correct chassis, deck, drive, handle, bagger parts | 917378490 |
| Engine model/type/code | Engine-specific parts (carburetor, ignition, recoil) | Varies by engine |
Why it matters
Using the correct mower model number prevents ordering the wrong drive, wheel, or handle parts. For example, the self-propel system parts list for this model includes items like the lawn mower ground drive belt, 3/8 x 33-9/16-in 532169778 and the lawn mower drive control assembly 532185685, which must match the exact mower configuration.
Quick ordering checklist
- Match the mower model number to 917378490
- Use the parts diagram key numbers from the manual when possible
- Confirm whether your mower is self-propelled and bag-capable
- Compare your existing part shape and mounting points before ordering
Last updated: January 2026
