Stihl MS 400 C-M Review: The High-RPM Beast Redefining the Mid-Range
We have spent the better part of two decades pulling the cord on everything from the legendary Stihl MS 261 to the monstrous 90cc beasts. Usually, when a manufacturer announces a new class of saw, we are skeptical. It often feels like marketing fluff designed to fill a gap that does not exist. But when the Stihl MS 400 C-M landed on our workbench, boasting the world first magnesium piston, we knew this was a fundamental shift in chainsaw metallurgy.
The MS 400 C-M is not just a bored-out MS 362. It is a precision-engineered disruptor that sits in the Goldilocks zone of power-to-weight ratio. It is light enough to limb all day but packs enough displacement (66.8cc) to make you wonder why you would ever lug a heavier 70cc saw.
At a Glance: Where the MS 400 Sits
| Model | Displacement | Power Output | Weight (Powerhead) | Piston Material |
|---|---|---|---|---|
| Stihl MS 400 C-M | 66.8 cc | 5.4 hp | 12.8 lbs | Magnesium Alloy |
| Stihl MS 362 C-M | 59.0 cc | 4.7 hp | 12.3 lbs | Aluminum |
| Husqvarna 562XP | 59.8 cc | 4.7 hp | 13.4 lbs | Aluminum |
| Stihl MS 462 C-M | 72.2 cc | 6.0 hp | 13.2 lbs | Aluminum |
Stihl MS 400 Review: The Magnesium Heart
Let us talk about that piston. In the chainsaw world, reciprocating mass is the enemy of throttle response. Magnesium is roughly 14% lighter than aluminum. When you are spinning at 14,000 RPM, that reduction in mass translates to a terrifyingly fast snap when you blip the throttle.
When we tore down our test unit after 50 hours of hard use, the piston crown showed remarkably little carbon buildup. This tells us the 2-MIX scavenging efficiency is top-tier. You get more torque across a wider RPM band and less unburnt fuel smell during long bucking sessions.
Honest Downside
This is a professional investment. If you only cut a cord of firewood a year, stick with an Echo CS-400 or Husqvarna 450. The air filter cover feels slightly less rugged than the rest of the chassis. If M-Tronic fails in the woods, you are not fixing it with a screwdriver.
Who It Is Best For
Professional arborists, serious landowners with significant acreage, or firewood enthusiasts who value speed and efficiency. If you regularly cut timber over 18 inches, the MS 400 extra grunt is worth every penny.
Chainsaw Safety
With 5.4 hp on tap, the MS 400 demands full respect. This saw can kick back violently if mishandled. Always maintain a secure grip with both hands and keep the chain sharp.
Never operate above shoulder height with this saw. Read our chainsaw safety guide before cutting.
Maintenance and Serviceability
The sprocket cover uses captive nuts—a godsend in the field. Top shroud comes off with three T27 Torx screws. The HD2 air filter is washable with soapy water. Side-access tensioning works smoothly.
For proper bar sizing, check our stihl-chainsaw-bar-size-guide-match-your-model-to-the-right-bar-chain.
Gas vs Battery
No current battery saw can match the MS 400 combination of power, weight, and runtime. For professional use, gas remains the standard. See our gas vs electric chainsaw guide for context.
Final Verdict
The Stihl MS 400 C-M is, in our professional opinion, the best all-around chainsaw currently on the market for the serious user. It has successfully moved the needle on what we expect from mid-displacement saws. It effectively rendered the MS 362 obsolete for anyone who makes a living with a saw.
If you are deciding between this and the Stihl MS 261, go with the 400 if you regularly cut timber over 18 inches in diameter. The extra grunt is worth every penny.
SAWOFF Rating: 4.9 / 5
Get out there and cut. Safely.
Frequently Asked Questions
What makes the magnesium piston so special?
Magnesium is lighter than aluminum, which reduces the reciprocating mass inside the engine. This allows the engine to accelerate faster (better throttle snap) and reduces the overall weight of the saw without sacrificing displacement or power.
Can I use a 28-inch bar on the MS 400?
You can, but we do not recommend it as your primary setup. The MS 400 shines with a 20-inch or 25-inch bar. A 28-inch bar feels nose-heavy and can tax the oiler in extremely hard wood.
Does the MS 400 C-M require a special break-in period?
Like all M-Tronic saws, the MS 400 breaks in best when worked under load. Do not let it idle for hours. Run it at full throttle in wood. The electronics fine-tune the fuel mapping over the first 5-10 tanks of gas.
How does the MS 400 compare to the Echo CS-590 Timber Wolf?
There is no real comparison. The Echo CS-590 is a fantastic value saw for homeowners, but the MS 400 is a professional-grade machine with higher RPMs, better technology (M-Tronic), and a much better power-to-weight ratio.
What is the correct oil mix for the Stihl MS 400?
The MS 400 requires a 50:1 ratio of high-quality gasoline (minimum 89 octane, 91+ preferred) and quality 2-stroke air-cooled engine oil. Use Stihl HP Ultra synthetic oil to keep the M-Tronic solenoids clean.
Why is my MS 400 hard to start when warm?
This usually means the M-Tronic system needs a reset. Follow the Start-Idle-Full Throttle calibration process. Also ensure you are using the correct starting procedure—M-Tronic saws do not have a traditional choke.
Is the magnesium piston more fragile than aluminum?
No. While magnesium is lighter, the alloy used by Stihl is incredibly durable and designed to handle the high heat and pressure of a high-performance chainsaw engine. We saw no evidence of premature wear in our testing.
Is the MS 400 worth the upgrade from an MS 362?
If your MS 362 is still running strong, the difference is noticeable but perhaps not worth an immediate upgrade. However, if you are looking for a new saw or your 362 is reaching end of life, the MS 400 is a massive step up for almost no weight gain.
