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Old 02-25-2019, 11:48 PM   #1
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Synthetic Oil In An Onan Generator

Good afternoon Thor owners,

I was just wondering. First, can you use synthetic oil in a generator? Secondly, can you use any brand such as Valvoline, MobilOne, etc.?

Thanks,

Andy
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Old 02-26-2019, 01:41 AM   #2
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Originally Posted by awong2683 View Post
Good afternoon Thor owners,

I was just wondering. First, can you use synthetic oil in a generator? Secondly, can you use any brand such as Valvoline, MobilOne, etc.?

Thanks,

Andy
Good question , I would call Onan and find out what they recommend.
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Old 02-26-2019, 02:03 AM   #3
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FIGURE 6. OIL FILL CAP AND DIPSTICK
Engine Oil Recommendations
Use API (American Petroleum Institute) performance Class SJ, SH or SG engine oil, which may be in combination with performance Class CH-4, CG-4 or CF-4 (for example: SJ/CH- 4).
Look for the SAE (Society of Automotive Engineers) viscosity grade. Choose the viscosity grade appropriate for the ambient temperatures expected until the next scheduled oil change.
Single-grade SAE 30 oil is preferable when temperatures are consistently above freezing. Multigrade oils are better when wide temperature variations are expected.
TABLE 10. OIL VISCOSITY VS. TEMPERATURE
Changing Engine Oil
EXPECTED AMBIENT TEMPERATURES
SAE VISCOSITY GRADE
0 C (32 F) and higher
30 (OnaMax)
12 to 38 C (10 to 100 F)
15W-40 (OnaMax)
18 to 27 C (0 to 80 F)
10W-30 10W-40
28 to 10 C (20 to 50 F)
5W-30


This is what is in my generator manual . I dont know if your is the same model.
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Old 02-26-2019, 02:45 AM   #4
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Synthetic

I cannot think of one reasonable reason why you cannot. I have been using it in mine since we bought the Axis. I think I have about 130 hours on it now. Here is the problem you will have. There is no 30 weight synthetic on the market. If anyone out there can find one, let us all know. Also, I use 15-40 which is typically used in diesel trucks and older Volvo autos. I used to find it in synthetic very easily, but now, nope. I was able to find a few brands in 15-40 synthetic and ended up with Royal Purple brand, ordered from Amazon. Oh yes, Schaeffer's out of St. Louis, MO, is the other one that has it.

https://www.schaefferoil.com/about.html
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Old 02-26-2019, 03:17 AM   #5
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Originally Posted by axis earl View Post
I cannot think of one reasonable reason why you cannot. I have been using it in mine since we bought the Axis. I think I have about 130 hours on it now. Here is the problem you will have. There is no 30 weight synthetic on the market. If anyone out there can find one, let us all know. Also, I use 15-40 which is typically used in diesel trucks and older Volvo autos. I used to find it in synthetic very easily, but now, nope. I was able to find a few brands in 15-40 synthetic and ended up with Royal Purple brand, ordered from Amazon. Oh yes, Schaeffer's out of St. Louis, MO, is the other one that has it.

https://www.schaefferoil.com/about.html
My 4000 Onan calls for 15w40. Can only find it for diesels. I called Onan and was told thats the proper oil to use.

Jerry
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Old 02-26-2019, 03:22 AM   #6
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The only reason the manual says to use 30 weight oil is because it does not break down as easily as multi weight oils. Synthetic oil also holds up better. I use it in every combustion engine I own. When my generator needs an oil change I will be putting Rotella T6 15-40 synthetic. Great oil and cheaper than most others.
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Old 02-26-2019, 03:58 AM   #7
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The reason the manuals don't list synthetic is because it doesn't translate in Chinese. Of course you can. For example Royal Purple. And it typically lasts twice as long as regular oil.

Cheers
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Old 02-26-2019, 04:53 AM   #8
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I use 15W-40 Rotella conventional oil, is also rated for diesel use. Now have 375 hours on it. No issues at all. Also use in trailer mounted RV ready champion that likely has 5 times as many hours.

I even use it in drag car engine (406 small block Chevy) with zero wear issues.

Synthetics have thier place, I have not seen any wear issues on engines I have pulled apart. Just opened up a 350 Chevy that was in drag car for 7 years. Only piston ring wear. I could reuse all engine bearings except they are not expensive. This engine has routinely been turned over 7,000 RPM. Always with Castrol GTX 20W-50 or a Mix of 20W-50 and 15W-40.
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Old 02-26-2019, 12:51 PM   #9
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Been running 10-30 Mobil 1 in ours, absolutely zero issues. I figure with our Florida summers, every little bit helps that little air cooled motor.
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Old 02-26-2019, 01:38 PM   #10
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Read your Owner's Manual specific to your make/model and do what it says...take the laptop to the toilet and read all this. You alone are responsible if you don't use what they recommend. Specs and designs change...I never thought, after driving and owning diesels for decades, that my new F550 6.7 diesel would call for a "5w" oil vs. the traditional 15w40 I've used in diesels all my life. "Only You Can Prevent Forest Fires".
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Old 02-26-2019, 01:47 PM   #11
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I would say so long as it meets the SAE severity ratings & viscosity, it should be fine to use synthetics.

The little I remember being taught about oils, in a multi-grade, it is man made polymers mixed into the oil (being straight weight to begin with), that makes it thicken its viscosity as its temperature rises, (the polymers binding together to force the oil to thicken).
Oil, will lose viscosity when its temperature gets hotter.
So,
In my honest opinion, and I am not the expert, since it is man made polymers in the mix, making it multi-grade viscosity oil, does that not make it semi synthetic?
Even though not advertised as such.

I remember our instructor, who engineered at Mobile Oil told us; that it is not recommended to mix different manufacturer's multi-grade oils, with others', as the polymers may not cohabitate equally while mixed and heated together.

This was 30+ years ago in a hydraulics class.
Things may be different now a days, but it was food for thought for a young apprentice.

I admit, I have needed a quart, while on the road, bought what was on the shelf to add to the engine, and I never experienced a problem, knowing full well it was different from what was in there.
But todays vehicles are built with tighter tolerances, and qualities are better.

I digress, just thought this will add...
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Old 02-26-2019, 02:02 PM   #12
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Gritz, I was surprised at the 0W-20 in our 2014 Altima. Have used Mobil 1 from start, now over 100,000 miles with no issue. I am not against Synthetics when it is specified by manufacturer.

Have a 2007 Suburban with 5.3 LS engine. I tried full synthetic and synthetic blend, both used oil rapidly. Normal oil usage was a half quart every 2,000 miles, both synthetics were more than double usage and no leaks. It has over 140,000 now on convenntional GTX.
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Old 02-26-2019, 02:05 PM   #13
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Agree...any oil is better than no oil in an emergency situation for a small period of time. Today's engines are built different...lighter, run faster, run hotter, etc. The oil lines are smaller to generate higher flow rates and quicker cooling. I worked for a major oil company for many years in the retail/dealer network...the days when the "pump jockey" pumped your gas, checked under the hood, tires, cleaned windows, etc. One of the hardest things I've had to accept is the changing technology. Today...go by what the Owner's Manual says...especially if it's under warranty. Even use their own "branded oil", even though they don't make it...your receipts will be your insurance policy in the event of a failure.
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Old 02-26-2019, 02:07 PM   #14
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Said it best, Gritz, I agree!
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Old 02-26-2019, 02:08 PM   #15
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Quote:
Originally Posted by Muggs View Post
Gritz, I was surprised at the 0W-20 in our 2014 Altima. Have used Mobil 1 from start, now over 100,000 miles with no issue. I am not against Synthetics when it is specified by manufacturer.

Have a 2007 Suburban with 5.3 LS engine. I tried full synthetic and synthetic blend, both used oil rapidly. Normal oil usage was a half quart every 2,000 miles, both synthetics were more than double usage and no leaks. It has over 140,000 now on convenntional GTX.

The wife's Cadillac uses Mobil One. I have to add twice between changes (every 5K regardless of what the computer says) and have since new. People don't realize this. Now it has 138K...if we don't trade it soon, I'm switching over to fossil fuel oil.
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Old 02-26-2019, 02:52 PM   #16
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The way I look at it is.... If the engine was designed for Synthetic then use Synthetic (never go to Dino oil). But if it says Dino oil or better .... then Synthetic is OK if thats what you want to do.

Keep in mind this tread is talking about an old school, air cooled, carbureted, single cylinder engine (Im assuming he has the Onan 4000 series) not a modern Car or truck engine that even seems to be talking about now.

Those two are miles apart..... as far as tech goes.

But I plan on changing to Synthetic oil on my Genny as well.... now that its broken in.
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Old 02-26-2019, 03:08 PM   #17
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By very nature air cooled engines have bigger clearances than a water cooled engine. I don't consider synthetics due to expense in this application. Neither the RV Onan or the trailer mounted Champion have required oil addition between changes yet. The Onan get changed every 125 hours due to not getting used much. The Champion on trailer gets changes much more frequently as on a race weekend it will run through night on Friday then after fillup and oil check it will run into Saturday night. If we are still in late, it get another fill and oil check then run into Sunday morning. For $300 the Champion is a killer deal, it goes 12 to 16 hours on 3.5 gallons of gas. It only holds 5/8 quart and I get many changes out of a gallon of Rotella 15W-40 for $12.97 at Walmart. I do tend to keep oil clean by changing frequently.
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Old 02-26-2019, 10:35 PM   #18
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I have ran synthetic oil in the generators for years to extend the run time between changes. Never an engine problem gas or diesel.

Our Polaris ATV's came with synthetic 0-40 oil way back when and later they went to 5-40 both which we changed oil at 200 hours as they sometimes had a harder life than the generators

The main difference in synthetic oil and fossil oil of the same grade is the uniform micron size of the molecules in the synthetic, if the Class is on the label matching your application go for it.

I also have run synthetic in all the vehicles and extended the change intervals as well. Always using a quality filter I might add. There is absolutely no need to change oil at the 3000 mile interval like a lot of the quick lube shops encourage you to do.
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Old 02-27-2019, 01:19 AM   #19
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I personally use synthetic oil in everything I own (gas powered)expect for my pickup which has a cummins 6.7l and the motorhome and generator they get conventional 15-40.

The reason I say this is because I work on diesel engines everyday and the company I work for is nation wide and are now experimenting with using a semi-synthetic oils in there on-highway trucks and we have lost a lot of engines both cummins and detroit to main bearing damage and I have tried it in my pickup which I change oil in every 5k miles but when I went to synthetic after around 1200 miles my change oil light came on and I changed it again with same oil and less than 1k miles did it again so I went back to 15-40 and my change oil light hasn't came back on since and ive done about 3 oils changes at 5k.

This is just my opinion based on what I see on my own vehicles and the ones I work on at work and is not based on any brands or any data we receive from delaers who by the way still use conventional oils.
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Old 02-27-2019, 01:43 AM   #20
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I only run synthetic in the vehicles where it is specified. 15W-40 Rotella in the Onan. I've been using that oil for years in my motorcycles and tractor. I really like it, because when new, it looks like B-grade maple syrup.
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