WOT RPMs are around 3000-3200 and I always ran my equipment at wot.

I have looked into this myself, and found at least two reasons to run my JD325 tractor at High Idle (3400 RPM), the speed you refer to as WOT. The first reason is to maintain the best mower blade tip speed for the best suction and cut. The second, was that I was told by Kawasaki tech support it is better for my Kawasaki 18 HP Air Cooled engine to be run at High Idle because it was designed to run cleaner that way. The Kawasaki Support person I spoke with said by running it at High Idle, there would be less chance of having a valve problem due to carbon buildup. He felt this would out weigh any benefits of trying to prolong the life of the engine by running it slower. He also recommended using a synthetic oil for better stability in hot weather, and lower operating temperatures. I have also heard it is better for the Hydrostatic Transmission as well, through better cooling from its external fan, as well as best overall operation. I have run my tractor this way for 9 years, with an average use of 50 to 60 hours per year. I change oil and filter once a year, and it never uses any oil. The owners manual for this tractor recommends oil and filter changes at 100 hrs, or every year. I also maintain a clean air filter. I'm sure some will disagree, but it sure works well for me. Charles Ranheim

I tend to go on the principle that the manufacturer generally knows more than I do.

So, here it is - straight from the horse's (Toro's) mouth:

From the Toro FAQ:

What are the benefits of running your riding mower on full throttle?

* Cleaner cut on the grass
* More power, less likely to bog down
* Less stress on the engine
* Engine runs cooler
* Slow engine speeds can result in hot spots on the cylinder
* In addition, many of these machines have hydrostatic transmissions that generate heat during operation. They have a fan that keeps them cool and the fan is driven directly by the engine. Running the engine less than full speed will frequently allow the transmission to overheat. The first sign is usually a lack of power on hills. Permanent transmission damage can result. By keeping the engine at full speed the operator will keep the fan at full speed. This will maximize the air flow for the transmission keeping it cooler and preventing premature failure.
* Riding products should be at full throttle at all times.

This is a lively topic so I expect I'll hear other opinions on this!

Full throttle. It's how your machine was designed to be used.

Anyone who's run large farm equipment (combines, etc.) knows that you run it up to full throttle and then control your speed with the hydro - a lawn tractor isn't any different. My Craftsman DLT2000 says to mow at full throttle, so that's what I do. And it has worked well for 7 years.

Dave- One more thing... your analogy about water-cooled engines would only apply if they also had preset governors on them. Running an air-cooled lawn tractor at WOT is completely different from a water-cooled car at red-line.

I run mine at WOT (governed, of course) because that is what JD recommends and they are the one that backs the warranty, so I am sure they did their homework before making the recommendation.

Say wot?? The big difference in operating an engine at WOT or less than WOT is determined by whether the engine really is running at WOT.....or if it is simply "running at governed RPM". If an engine is designed and built with a governor to keep the engine RPM below an arbitrary MAXIMUM RPM, it is perfectly OK to operate the engine at that RPM....continuously. In fact, a lot of engines that feature a governor, are operated at governed RPM throughout most of their life. You only have to consider all the big trucks on the highways to see the largest population of governed engines.
On the other hand, trying to run an "ungoverned" engine at WOT will result in total destruction of the engine in a matter of seconds.
The old arguments (countless) about low RPM being "easier" on the engine and "producing less wear"......are groudless.
When an engine is run at low RPM, the lubrication of the engine is less effective, whether pump or splash (but we're splitting hairs here).
As to cooling, the higher RPM circulates the cooling medium with greater force and velocity (and volume) at higher RPM, so cooling is more effective at higher RPM.
Water pumps, and cooling fans, are both "centrifugal pumps" or movers. At very low RPM, either of these components could theroretically rotate WITHOUT moving any of the medium they are "immersed in" (whether air of liquid). The reason is because the medium exerts a certain resistance to the impeller to set the mass of the medium into motion. If you move the impeller (or "fan blade") slowly enough, the medium simply moves off the outer edge of the impeller and flows around the end of the impeller to the backside of the impeller without influencing any more of the medium mass than is situated inside the water pump, or fan housing. In order for a centrifugal pump or mover to actually affect "flow" into and out the housing, the impeller must be spun at a fairly high RPM. So, if you think you are "saving the engine" by shifting to a higher gear so the engine can turn slower, you could be doing more harm than good. Shifting to a higher gear actually increases the pressure applied to the crankshaft rod and main journals as well as the piston wrist pin. By shifting to a higher gear, you are denying the engine the benefit of "power multiplication" offered by the lower gears in the transmission. Because the throttle must be opened wider for the engine to operated in a taller gear, the combustion pressures in the cylinder increase dramtically in contrast to using a lower gear with less throttle.
Sounds contradictory? Almost.
The best RPM to operate an engine is the RPM that allows the engine to accomplish its job without bogging down or lugging down, If an engine is being operated at the proper RPM for the load, that engine will be able to accept an increase in load, without having to downshift to a lower gear. If the engine RPM can not be maintained without down shifting, you are putting too much pressure on the crankshaft AND, probably don't have the best lubrication as well. This is a very general description of why it is best to err on the side of caution, and in this case, "caution" lies in the higher RPM range (and lower gears).

To paraphrase, mownie thinks you should run your mower at the governed RPM (which you call WOT).

>>>> To paraphrase, mownie thinks you should run your mower at the governed RPM (which you call WOT).

LOL :)

And Mownie is correct!

Yeah... Once you realize wot in not "red line" speed, but rather maximum governed speed, it gets easier. other than best lubrication and cooling, it should also run near the most optimum range in the power and torque curves giving more efficient power under different load conditions. Less bogging down, faster recovery, etc.

But also consider that the transaxle, mower deck and other PTO accessories are also designed to operate most efficiently at specific RPMs. All those pulleys (sheaves) aren't just grabbed off the shelf randomly. They are specifically sized to operate these devices most efficiently from a given engine RPM.

All this stuff is inter-related. So, everything will be happier and run better if we simply let the engine run at the speed it was designed (and governed) to run. Yeah, wot.

My Stihl string trimmer dealer told me it like to either idle or flat out run with WOT nothing in between FWIW

Lot of good info here.The old Kohler "K" doesn't have full pressure lube,so the slinger needs full rpm to keep it lubed properly under load.

So,there you have it Dave.Open it up and let it eat.Quit doggin' it :-)

After reading Mownie, I should have originally said wide open throttle cable. The actual throttle is governed and isn't wide open at all.