View engine
Should I use 87 or 91 gas for lawn mower?
For the Craftsman 917374390 gas walk-behind mower, we recommend using 87 octane (regular unleaded) in normal conditions. Higher octane like 91 does not add power or “clean” the engine; it is mainly for high-compression engines and can make a small mower harder to start if the fuel is old.
What fuel to use (and what matters more than octane)
- Use fresh, clean unleaded gasoline; stale fuel is the most common cause of hard starting.
- Choose 87 octane unless your engine label specifically calls for higher.
- Prefer ethanol-free fuel when available; if not, keep ethanol content at 10% or less (E10).
- Add fuel stabilizer if the gas will sit more than 30 days.
- Store fuel in an approved container and keep the mower’s tank cap area clean to prevent debris from entering.
Quick comparison: 87 vs 91 in a walk-behind mower
| Fuel choice | Best use | What you will notice |
|---|---|---|
| 87 octane (regular) | Everyday mowing | Normal power, normal starting |
| 91 octane (premium) | Only if the engine specifically requires it | Typically no benefit in power or reliability |
If your mower runs rough after refueling
Try these checks before replacing parts:
- Drain old gas and refill with fresh 87 octane.
- Inspect the air filter and spark plug condition.
- Check for water in the fuel (milky look or phase separation).
- Make sure the blade area is clear; heavy grass buildup can load the engine.
If you’re servicing the blade during a tune-up, use the correct hardware and tighten securely; a worn fastener can loosen over time. The lock nut 532409149 is one of the common fasteners used on this model.
Why it matters
Using the right fuel helps prevent varnish in the carburetor, hard starting, surging, and stalling. In small engines, fuel freshness and ethanol content affect performance far more than choosing 91 over 87.
Last updated: January 2026
What model number is the Craftsman 917374390?
The model number for this Craftsman walk-behind lawn mower is 917374390. You will typically find 917374390 on the mower’s model and serial number label, which is used to match the correct replacement parts (like belts, blade hardware, and drive components).
Where to find the model number on the mower
On most Craftsman walk-behind mowers like model 917374390, the model/serial label is commonly located in one of these spots:
- On the rear of the mower deck near the discharge opening
- On the top of the deck near the engine mounting area
- Near the rear wheel height adjuster area
- On the handle support bracket (varies by deck design)
Why the exact model number matters
Using the exact model number helps us match the correct parts list for your mower’s specific build. Even small differences can change which belt, fasteners, or drive parts fit.
- Ensures the correct self-propel drive parts are selected
- Prevents ordering the wrong blade mounting hardware
- Helps match the correct deck and wheel components
- Improves troubleshooting accuracy for “won’t move” or vibration issues
Common part examples tied to model 917374390
Here are a few examples of parts that are selected by model-specific fit:
| Part type | Example from this model’s parts list | What it affects |
|---|---|---|
| Drive belt | Belt 532157769 | Self-propel movement |
| Blade mounting component | Lawn mower blade adapter 581547901 | Blade fit and cutting performance |
| Drive gear | Lawn mower drive pinion gear 532137054 | Wheel drive engagement |
Quick tip before ordering parts
Double-check that the label reads 917374390 exactly (including any dashes or additional numbers if present). If the label is worn, clean it gently and take a photo before it fades further.
Last updated: January 2026
What year is my Craftsman mower serial number lookup?
On a Craftsman mower like model 917374390, the year is typically encoded in the serial number or date code on the ID label; many labels use a MMDDYY style date (month, day, year). Once you find that code, the last two digits usually indicate the year.
Where to find the serial number or date code
Look for the ID label in common walk-behind mower locations:
- Rear of the deck near the discharge opening
- Top of the deck behind the engine
- Near the rear wheel height adjuster area
- On the handle support bracket
- Under the grass bag door area
If the label is dirty or faded, wipe it with a damp rag and mild cleaner so the stamped characters are readable.
How to decode the year (common formats)
Craftsman and OEM suppliers used a few different label styles over the years. Here are the most common patterns we see:
| What you see on the label | What it usually means | Example result |
|---|---|---|
6 digits like 072811 |
MMDDYY date code | July 28, 2011 |
8 digits like 20110728 |
YYYYMMDD date code | July 28, 2011 |
| Serial with letters and numbers | Date may be embedded, or separate “DOM” line | Use the printed date line if present |
Quick check
- If you see six digits, read them as month, day, year.
- If you see eight digits starting with 19 or 20, read them as year, month, day.
Why it matters
Knowing the build year helps us match the correct parts and revisions for your mower, especially for wear items like the drive system and blade mounting hardware.
If you are servicing the blade area while you confirm the model and date code, use the correct fasteners and hardware for safe reassembly, such as the lawn mower blade adapter 581547901 and the correct lock nut 532409149 when applicable.
Tips if the label is missing
- Check for a second label on the handle bracket or rear deck panel
- Compare your mower’s drive setup to common wear parts (belt-driven self-propelled systems often need periodic belt replacement)
- If the mower will not self-propel, follow a motion-drive diagnostic path like lawn mower wont move troubleshooting video motion drive failure
