The 38 hp Kohler engine option sounds like you are really getting more power, but when you read this (J1995 Power 3 34.2) in the engine specs it tells the real story. J1940 allows the engine manufacturers to add up to 15% of actual hp and list it in that manner for advertising purposes as so-called gross hp. This means by showing a 38 hp rating they are staying well within the parameters of the J1940 classification by being only 10% above the true usable hp which is 34.2. To prove this I am listing below information Kohler includes in their specifications. QUOTE: "Kilowatt (kW) and gross torque (fl-lbs) specifications for Kohler general purpose engines are calculated pursuant to the Society of Automotive Engineers (SAE) J1940 - calculated with the air cleaner and muffler removed, per the SAE standard. Actual engine gross torque are lower and affected by, but not limited to, accessories (air cleaner, exhaust, charging, cooling, fuel pump, etc.), application, engine speed and ambient operating conditions (temperature, humidity and altitude)." J1995 Power Certified by 3rd Party Witness TJ1995 Power 3 34.2 / This is the usable hp of the Kohler CV980 38 hp engine The Kawasaki engines are now power-rated to a tighter, automotive-caliber SAE J2723 standard, which they tell you will keep their listed hp within 2% of actual usable hp at all times. Kawasaki has now listed their FX1000V (37 hp at the old rating) at 35 hp under the closer tolerance rating system, and what this means is...they are guaranteeing their 35 hp listing to be with 2% of actual hp...2% of 35 = .70 hp which equates to in a worst case scenario their listed 35 hp engine may in actuality have a true 34.3 hp, but guaranteed to be no less. You now have the average person buying a mower with what he believes to be a Kohler 38 hp engine, when in reality it is a 34.2 hp engine. He bought the mower with this engine for the fact of believing he was getting 3 more hp over the 35 hp Kawasaki engine, when really the Kawasaki 35 hp engine had more usable hp than the Kohler 38 hp engine, not but 1/10 of a hp, which is non-detectable, but would still be greater.