Owner’s manual
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What kind of gas do I put in my lawn mower?
For the Craftsman lawn mower model 917388940, we recommend using fresh regular unleaded gasoline; in most walk-behind mower engines, E10 (up to 10% ethanol) is the right choice, while premium high-octane fuel is unnecessary.
Recommended fuel for model 917388940
Use fuel that matches these basics:
- Regular unleaded gasoline
- E10 or less (up to 10% ethanol)
- Fresh fuel (best within about 30 days, or stabilized for storage)
- Clean, water-free gas from a sealed container
For any model-specific notes (fuel grade, storage guidance, or special cautions), follow the 917388940 owner's manual.
What to avoid
Avoid fuel choices that commonly cause hard starting, surging, or carburetor issues:
- Old gasoline (stale fuel is a top cause of no-start)
- Higher-ethanol blends (often labeled E15, E20, E85)
- Gas contaminated with water or dirt
- Mixing oil into the gas (this model is typically a 4-cycle mower; oil goes in the crankcase, not the fuel tank)
Quick fuel decision table
| Fuel type | Use it? | Why |
|---|---|---|
| Regular unleaded (E0) | Yes | Clean burn; great for small engines |
| Regular unleaded (E10) | Yes | Common and compatible for most mowers |
| Premium unleaded | Usually not needed | Higher octane does not add power in mower engines |
| E15 or higher ethanol | No | Increases risk of fuel-system problems |
Why it matters
Correct fuel helps the engine start easily and run smoothly, and it reduces varnish buildup that can clog the carburetor and fuel passages during storage.
Helpful related DIY guidance
If fuel issues show up as hard starting or repeated stalling, use our how to keep lawn mower gas from going bad tips to prevent stale-fuel problems.
Last updated: January 2026
What model number is the Craftsman 917388940?
The model number is 917388940. On this Craftsman walk-behind gas lawn mower, you’ll typically find that number on the mower’s model and serial tag; match it exactly when ordering parts or using the 917388940 owner's manual.
Where to find the model number on the mower
Look for a sticker or metal tag in one of these common spots:
- Rear of the deck near the discharge opening
- Top of the deck behind the engine
- Near the handle mounting brackets
- On the rear door or bagging area (if equipped)
- Under the deck lip (wipe grass and dirt off first)
How to confirm you have the right number
Use these quick checks before you buy parts like a blade adapter or wheel:
- The model number should read 917388940 (no extra letters or spaces)
- Record the serial number too; it helps identify production variations
- Compare the tag to the model number shown on the 917388940 owner's manual
- If the tag is worn, clean it gently and use a flashlight at an angle
Why the exact model number matters
Craftsman walk-behind mowers often have multiple versions that look similar. The exact model number ensures the correct fit for items like the zone control cable, mulcher door, discharge guard, and 21-in deck blade.
Common identifiers (quick reference)
| Item | What it tells you | Example |
|---|---|---|
| Model number | Which parts diagram and parts list to use | 917388940 |
| Serial number | Production run details | Varies |
| Engine model/type | Engine-specific tune-up parts | Varies |
Last updated: January 2026
Where is Craftsman's model number?
On a Craftsman walk-behind mower, the model number is typically on the mower’s main ID label (not the engine) and is easiest to find on the deck housing near the rear or side. For this mower, the model number you’ll use for parts is 917388940.
Where to look on Craftsman model 917388940
Check these common label locations first:
- Rear of the mower deck, near the height adjuster or rear wheels
- Left or right side of the deck, just above the cutting height positions
- Under the rear discharge door or near the bagging opening
- On the handle bracket area where the handle mounts to the deck
- Near the engine mounting area on the deck (label is on the deck, not stamped into the engine)
For diagrams and the exact label callouts used on this model, use the 917388940 owner's manual.
Model number vs. engine numbers (why they are different)
Your mower has two sets of identifiers: one for the mower and one for the engine. Use the mower model number for chassis parts like wheels, handles, and discharge components.
| What you are identifying | What it helps you find | Where it is usually located |
|---|---|---|
| Mower model number (917388940) | Deck, wheels, handle, blade adapter, chute parts | Sticker/plate on the mower deck |
| Engine model/type/code | Engine tune-up and internal engine parts | Label or stamping on the engine |
If the label is missing or unreadable
Use these practical workarounds:
- Clean the deck with a damp rag and mild cleaner; grass film can hide the print
- Look for a second sticker location on the opposite side of the deck
- Match parts by diagrams using the mower model number 917388940
- If you are replacing common hardware, confirm size and thread before ordering
If you are working on the discharge area, the discharge guard 589482402 is a common model-matched part to reference when confirming fit.
Why it matters
Using the correct model number prevents ordering the wrong Craftsman walk-behind mower parts, especially for deck-mounted items like the blade adapter, wheels, and handle brackets where small design changes affect fit.
Last updated: January 2026
