Very specific use oil weight question

[Zerxez]

This is my first post, not a lub-nube but a semi-complex question: I just bought a Kohler 20kw air-cooled 3600rpm generator with a CH1000 series engine. The application is for the backup of a solar power system. The plan is to run it (after warm-up) at 90-100% load for 3-4 hours a few times a year when the battery bank gets too low due to weather or other problems. The location is at 8,500ft in Colorado. The air is thin, so the generator will tend to run hot. However, it will probably run the most when the insolation is least (winter) at -25 to 30 degrees F, but there will be times it will run in all seasons with ambient temperatures up to 100°F.
The generator owner's manual says 5w-30 synthetic, the CH1000 engine owner's manual says 10w-50 synthetic. The engine is used in lots of applications, from riding lawn mowers to pumps and construction machines. However, a generator will run at 3600 rpm all the time.
Because it will start when the batteries reach a low state of charge, after warm-up, it will run for an average of 3.5 hours every time it is run. For efficiency, it makes sense to load it heavily.
Running at 3600 rpm at a high altitude under heavy load, what is the best weight oil in summer and winter? I have already decided it must be a 0w-xx oil because of winter starting temperatures. In the summer, it can get over 100°F with thin air/poor cooling, so am I better off running a 0w-30, 40, or 50?
If possible, I want to change the oil only once a year, with probably no more than 16-32 hours of run time per year.

 

[Cujet]

As always, the wider the viscosity spread, the more VII's the oil uses, and the more the oil will shear over time. I took a quick look in the owners manual and nowhere does it recommend a 0W oil. The 10W-50 is for all temps, and the 5-30 is for 32 and below.

Consider a robust, synthetic 5W-40. I have been using Rotella T6 5W-40 in my Kawasaki powered JD GT235 garden tractor for the last 23 years. Still works like a champ. Holds up to the FL heat just fine.

 

[kschachn]

As always, the wider the viscosity spread, the more VII's the oil uses, and the more the oil will shear over time. I took a quick look in the owners manual and nowhere does it recommend a 0W oil. The 10W-50 is for all temps, and the 5-30 is for 32 and below.

Consider a robust, synthetic 5W-40. I have been using Rotella T6 5W-40 in my Kawasaki powered JD GT235 garden tractor for the last 23 years. Still works like a champ. Holds up to the FL heat just fine.

This.

And an oil with a 0W winter rating is only needed below about -30 or so.

 

[Opelman]

I'd go with the Amsoil made 10-50 Kohler oil. Good stuff and when combined with the "special" filter, is rated for a 300 hr. service interval. I personally wouldn't go that long but a few bucks more for peace of mind is worth it.

 

[repairman54]

First off since you see real subzero temps in winter you should put the cold weather kit in it for reliable winter starts.
With a winter heater kit, it will start fine with 5w bottom number oils. 40w top numbers will be fine.
My standby Generac's with the cold weather kits run fine on 5-30w synth. oils. I see -20f regularly in winter.
Record high summer temp. in my area is 93f, so I'm fine with the 5-30w oil.
On my 2nd standby gen. set with the newer house now.
IMO your biggest concern is winter starting, that is when power is needed to keep things from freezing up.
Warmer oil means better winter cranking, along with less stress with a warmer battery with the cold weather kit.
I don't know about your unit, but my air-cooled Generac's have an oil cooler, so I have no worries about running a 5-30 all year.

 

[Zerxez]

Thank you all so much for the excellent information. It got my brain working on the whole environmental process.

The generator does have an oil cooler. There are only 3-5 days a year that are over 100 degrees, and I can avoid starting on those days by simply noticing if it has been cloudy and running it before the batteries get too low. At night, the temperatures drop to the high 70s/low 80s. In fact, it makes no sense to run it during the day since we always get much lower temps at night in the mountains. I will program the auto-start to wait until the hours after dark and set the low-battery auto start to a higher voltage. So if the batteries are low in the morning, there will still be enough charge to get through the daylight portion of the day.

The new plan (if everyone agrees) is to run 5W-30 and the generator only at night in the summer and only during the day in the winter. I also have a couple of portable generators that will get me through a tough spot. So, I will only perform exercise runs every three months (the manufacturer recommends monthly) and time them to avoid the hottest and coldest months. I will monitor the run temps just in case the thin air up here causes it to run too hot. Hopefully, I sized the solar array and battery bank so that it would never have to run, but...

Please confirm this is a good plan, or point out what I have missed. Once the generator has some wear, I can always bump up to a thicker oil if needed.

 

[The_Eric]

Sounds like a good plan. Since you have an oil cooler, that helps quite a bit.

Also remember that being air cooled, your engine temps are directly tied to ambient.. so no need for heavy oil in sub zero temps. Heck, they may not ever rise above 120-150 degrees if it's cold enough. There was another member here who had a GX630 or similar sized Honda which operated in the cold and he ended up mostly or completely blocking off the blower housing inlet to get temps up.. I want to say that they were as low as 80 or100F before blocking.

 

[oil pan 4]

This is my first post, not a lub-nube but a semi-complex question: I just bought a Kohler 20kw air-cooled 3600rpm generator with a CH1000 series engine. The application is for the backup of a solar power system. The plan is to run it (after warm-up) at 90-100% load for 3-4 hours a few times a year when the battery bank gets too low due to weather or other problems. The location is at 8,500ft in Colorado. The air is thin, so the generator will tend to run hot. However, it will probably run the most when the insolation is least (winter) at -25 to 30 degrees F, but there will be times it will run in all seasons with ambient temperatures up to 100°F.
The generator owner's manual says 5w-30 synthetic, the CH1000 engine owner's manual says 10w-50 synthetic. The engine is used in lots of applications, from riding lawn mowers to pumps and construction machines. However, a generator will run at 3600 rpm all the time.
Because it will start when the batteries reach a low state of charge, after warm-up, it will run for an average of 3.5 hours every time it is run. For efficiency, it makes sense to load it heavily.
Running at 3600 rpm at a high altitude under heavy load, what is the best weight oil in summer and winter? I have already decided it must be a 0w-xx oil because of winter starting temperatures. In the summer, it can get over 100°F with thin air/poor cooling, so am I better off running a 0w-30, 40, or 50?
If possible, I want to change the oil only once a year, with probably no more than 16-32 hours of run time per year.

Read the manual. You'll likely find that you're not supposed to run it continuously at more than half the "rated load" for more than anywhere from 5 to 20 minutes at a time.

 

[Zerxez]

Thank you, oil pan 4, I looked it up and they recommend a .8 power factor/80% load, mostly so there is headroom for A/C motor starts, etc. That said, you make a very good point. Higher loads put more wear on the generator, so I will research load wear vs run time. In my application, at 90% load, it will take about 3.5 hours to charge the batteries. At 50% load, it would have to run about 7 hours at the same 3600 rpm. I will research to determine the most efficient use between power factor, run-time, and system wear. That will require at least one call to Kohler.

 

[oil pan 4]

Thank you, oil pan 4, I looked it up and they recommend a .8 power factor/80% load, mostly so there is headroom for A/C motor starts, etc. That said, you make a very good point. Higher loads put more wear on the generator, so I will research load wear vs run time. In my application, at 90% load, it will take about 3.5 hours to charge the batteries. At 50% load, it would have to run about 7 hours at the same 3600 rpm. I will research to determine the most efficient use between power factor, run-time, and system wear. That will require at least one call to Kohler.

Not really more wear, it over heats the generator.

 

[oil pan 4]

If you're just charging batteries why not use an alternator setup?
Just generate the voltage you need instead of making 120v at 3600rpm, then stepping it down.
An alternator setup can run any speed, around 2,200rpm is usually ideal for fuel economy on these little engines.

 

[Zerxez]

I will run an alternator setup once this generator ages out. However, this house is new construction, and the inspector is very picky about what he will and won't allow. Because the State of Colorado does not recognize off-grid solar as a "reliable" power supply, I must have an A/C generator to meet code. Yes, this is ridiculous because I have had multiple power outages at my current grid-connected home, and when I was previously on solar, I didn't have any. But the law is the law. When this Kohler generator eventually fails, there shouldn't be any inspections, and I can do it right.

As to engine wear, if it starts to get too hot (only in summer), I won't have a choice but to reduce the load. In winter, running a heavier load, maybe even 100%, will make sense to offset the sub-zero atmospheric temperature. I will monitor the running temperature in both seasons and adjust as needed. I doubt it will run much, if ever, in summer since there are many more hours of sun for the solar panels.