Onan Generator Oil Change

[BC-ClassC]

Hi, I have an Onan generator that is due for an oil change. It is the end of camping season here in BC, Canada. Is it best to change the oil now while winterizing our Class C motorhome (Thor Four Winds 28E) or do it in the Spring when we prepare the RV for the new season camping? Thanks!

[Chateau_Nomad]

Originally Posted by BC-ClassC

Hi, I have an Onan generator that is due for an oil change. It is the end of camping season here in BC, Canada. Is it best to change the oil now while winterizing our Class C motorhome (Thor Four Winds 28E) or do it in the Spring when we prepare the RV for the new season camping? Thanks!

I change the oil in ours per the book OR at the end of season before storage. My reasoning is that I "exercise" the generator even during the winter, and I want clean oil in it. There's one less thing to do in the spring... that's when I change the coach engine's oil. Actually, I don't think it makes any difference WHEN... the important criteria is follow the Onan guide (manual) as well as the operation (exercise). DON'T let it sit for several months without starting/running. Same for the coach engine!

[Muggs]

We are in Florida so never store as it sits in yard plugged in.

If unit sits more than 2 weeks, I run generator with A/C on very cold for 30 to 45 minutes. Oil changes are annual per manufactirer specs. We bought with 200 hours and it has 560 after 5 years.

Exercising it gets fresh fuel through carb and prevents fouling from old gas.

We tow a drag car and trailer generator gets most use as we start in on arrival and only shutdown to check oil/refuel omce a day. Has at least 5000 hours by now.

[EA37TS]

Since the generator should be exercised while in storage does the average winter temp necessitate a change in oil viscosity? You may need to change it before and after storage.

[happy]

Tests on piston aircraft engine show that rust begins to form inside the engine within several days of sitting idle. Not engine eating rust, but rust
nonetheless.


Nothing wrong with changing the oil when going into winter storage....removes the "stuff" that is in your oil. But as mentioned by those above, excercise your engines to bring them up to operating temperature from time to time.

[Chateau_Nomad]

EDIT - I had to go look at my maintenance log! Then corrected...

I use 10W-30 in mine year round in Ohio, which protects down to 0 degrees F. The temperatures here rarely stay lower than that over an extended period. If they do dip below that, I simply wait until the temperature rises to within range... usually not longer that a week.

Here's a chart directly from the Onan handbook:

[waynetaylor55]

From the Onan Manual:

4.5 Exercising the Generator Set

Exercise the generator set at least 2 hours each month if use is infrequent. Run the generator set at approximately 1/2 rated power. A single 2-hour exercise period is better than several shorter periods.

[Muggs]

Originally Posted by happy

Tests on piston aircraft engine show that rust begins to form inside the engine within several days of sitting idle. Not engine eating rust, but rust
nonetheless.


Nothing wrong with changing the oil when going into winter storage....removes the "stuff" that is in your oil. But as mentioned by those above, excercise your engines to bring them up to operating temperature from time to time.

In the race motor same thing happens, rust forms on exposed metal in combustion chamber as it always stops with exhaust valve open to open headers. If car is going to be stored for more than 2 weeks I squirt two cycle oil down carb to slow rust. Florida with temp swings and humidity guaratee moisture buildup in anything with open crankcase.

I use 15w40 in all the generators, we do not see real temps below 30 in central Florida often. If I was seeing below 0 would go lighter.

[Chateau_Nomad]

Originally Posted by Muggs

In the race motor same thing happens, rust forms on exposed metal in combustion chamber as it always stops with exhaust valve open to open headers. If car is going to be stored for more than 2 weeks I squirt two cycle oil down carb to slow rust. Florida with temp swings and humidity guaratee moisture buildup in anything with open crankcase.

I use 15w40 in all the generators, we do not see real temps below 30 in central Florida often. If I was seeing below 0 would go lighter.

I have a 15 year old "head banger" 6.5k generator I keep in the garage for emergencies. I never leave gas in it - and I change the oil every year. I DO NOT exercise it like I do the ONAN. I had a lawnmower mechanic tell me years ago... If your small engine is going to sit for an extended time in storage, pull the spark plug and spray a few shots of WD-40 into the cylinder. Then crank the engine over slowly a few revolutions with the pull rope starter. Stop the piston TDC, then replace the plug.

I have followed those instructions to a T... and it fires up FIRST PULL every time! It smokes a little from the WD, but it quickly burns off. NO rust in the cylinder!! If not used, I only start it around first of November to make sure it's good for an emergency "no heat situation" during winter.

P.S. Ethanol fuel is NASTY STUFF. Don't leave it sitting unused in your power equipment!

[Muggs]

The race motors run pump premium from high tier stations. Under $4 vs $12 for 110 race gas and it allows me to get gas before pulling into track. Rust forms quickly just from temp changes in Florida humidity. Alternatives such as e85/methanol can work but seem to be worse for moisture absorption.

I cycle stuff frequently to keep fresh fuel in bowls. Just replaced a 5500 Generac flathead we bought just before hurricane Andrew back in 1992. The champion RV ready gen on racecar trailer gets used enough fuel rarely sits in it. I pulled bowl looking for rust after 5 years and found none.

Ethanol at 10% or less has bot been an issue. Would never let it sit more than 30 days. Leftover premium at end if race weekend goes into whatever needs gas at house. Always replace before race weekend.

[Mgtv53]

Originally Posted by BC-ClassC

Hi, I have an Onan generator that is due for an oil change. It is the end of camping season here in BC, Canada. Is it best to change the oil now while winterizing our Class C motorhome (Thor Four Winds 28E) or do it in the Spring when we prepare the RV for the new season camping? Thanks!

Yes changed so you can exercise it for half an hour twice a month

[EA37TS]

Originally Posted by Mgtv53

Yes changed so you can exercise it for half an hour twice a month

Onan recommends 50 percent load for 2 hours every 4 weeks for gas powered generators.

From the Onan Handbook


Exercising Your Generator

It may seem surprising that “not” using a machine could cause performance problems, but with RV generators that’s exactly the case. Regular “exercise” is an important part of keeping your generator healthy. Lack of exercise can cause moisture build-up and fuel system degradation that make it run poorly. In fact, in as little as 30 days, the fuel in gasoline-powered generators can begin to gum and varnish the fuel system. Fuel varnishing results in hard starting and surging. (A surging generator never settles at a stable operating speed.)

To prevent such problems, it is recommended to run gasoline generators at a minimum of 50 percent capacity (2000-watts, or one air conditioner for a 4000-watt set) for two hours once every four weeks. This is necessary to help keep moving parts lubricated, expel moisture and control fuel varnishing in the carburetor. A long two-hour exercise period is preferable to several short periods. While traveling, this can be accomplished by running the air conditioning. If you own a diesel generator, regular exercising can help reduce internal condensation and helps keep seals lubricated.

[Muggs]

Originally Posted by EA37TS

Onan recommends 50 percent load for 2 hours every 4 weeks for gas powered generators.

From the Onan Handbook


Exercising Your Generator

It may seem surprising that “not” using a machine could cause performance problems, but with RV generators that’s exactly the case. Regular “exercise” is an important part of keeping your generator healthy. Lack of exercise can cause moisture build-up and fuel system degradation that make it run poorly. In fact, in as little as 30 days, the fuel in gasoline-powered generators can begin to gum and varnish the fuel system. Fuel varnishing results in hard starting and surging. (A surging generator never settles at a stable operating speed.)

To prevent such problems, it is recommended to run gasoline generators at a minimum of 50 percent capacity (2000-watts, or one air conditioner for a 4000-watt set) for two hours once every four weeks. This is necessary to help keep moving parts lubricated, expel moisture and control fuel varnishing in the carburetor. A long two-hour exercise period is preferable to several short periods. While traveling, this can be accomplished by running the air conditioning. If you own a diesel generator, regular exercising can help reduce internal condensation and helps keep seals lubricated.

This is true for virtually all gas powered equipment even prior to addition of ethanol. I just replaced my old flathead generator from Hurricane Andrew back in 1992. It worked fine on 10% ethanol after I modified carb a little. It was loud and killed mosquitoes but ran through all the outages for either my house or a neighbor. I use shorter run than Onan recommends but unit is never in storage.

[BC-ClassC]

I appreciate the advice and did the oil change. I also have set up a schedule to run the generator a couple of hours per month based on the replies on this thread to keep everything lubed. I used 15W-40 as it states in the manual that is acceptable for gas generators, although the oil itself says for diesel engines. Hope this is correct.

[Jimbo56]

Originally Posted by Chateau_Nomad

I have a 15 year old "head banger" 6.5k generator I keep in the garage for emergencies. I never leave gas in it - and I change the oil every year. I DO NOT exercise it like I do the ONAN. I had a lawnmower mechanic tell me years ago... If your small engine is going to sit for an extended time in storage, pull the spark plug and spray a few shots of WD-40 into the cylinder. Then crank the engine over slowly a few revolutions with the pull rope starter. Stop the piston TDC, then replace the plug.

I have followed those instructions to a T... and it fires up FIRST PULL every time! It smokes a little from the WD, but it quickly burns off. NO rust in the cylinder!! If not used, I only start it around first of November to make sure it's good for an emergency "no heat situation" during winter.

P.S. Ethanol fuel is NASTY STUFF. Don't leave it sitting unused in your power equipment!

Kind of hard to get the onboard genny to stop TDC. But I do as you do for my 12000 watt home generator.

[Chateau_Nomad]

Originally Posted by Jimbo56

Kind of hard to get the onboard genny to stop TDC. But I do as you do for my 12000 watt home generator.

TDC just keeps the ports/valves closed for long-term storage... not really an issue if using the onboard Onan on a regular basis. Besides, without the ability to hand-crank, it's hit or miss... mostly miss!

[Muggs]

I have had zero issues using diesel oil (15w-40) in any gas engine including race motors. It used to have a higher load of zinc which helped flat tappets. Even with lower levels of zinc I have had zero issues. Bearings out of race motors look new after 5 or 6 seasons.

Onan says 15w40 is fine and it is found everywhere at reasonable cost. I would always follow manufacturer specs on newest vehicles with VVT and some of the cam phasing requiring no heavy viscosity oils.