synthetic oil for onan generator

[KatanaPilot]

Originally Posted by nicktano

I went to Cummins to buy oil for my Onan diesel generator 3200, in my MBS 2401R Forrester. I asked for synthetic but was told by the service and parts departments to only use regular oil. So I have only been using regular. I don't know why but the Cummins folks said that they would not recommend using synthetic in their generators. Got me?

I use Amsoil diesel oil for my QD3200 Cummins/Onan with the Hatz engine. Great oil, no issues and I can't understand why the dealer would recommend dinosaur oil - unless that's all they sell.

The only application I have found that synthetic oil is inferior to dinosaur oil is air cooled airplane engines burning leaded fuel.

[Springerdad]

Originally Posted by KatanaPilot

The only application I have found that synthetic oil is inferior to dinosaur oil is air cooled airplane engines burning leaded fuel.

Is that because of getting certification? Or is it oil additive formulaion? Curious.

[KatanaPilot]

Originally Posted by Springerdad

Is that because of getting certification? Or is it oil additive formulaion? Curious.

Quite a few years back, Exxon introduced a full synthetic aviation grade oil. It was pulled from the market after a while, as it was discovered that full synthetic oil did not scavenge the lead (present in the fuel) adequately. So the lead gummed up valves, rings, etc. The lubrication properties were fine.

There are semi-synthetics in use now that work well and with the pending introduction of lead-free aviation fuel, we may see a re-introduction of full synthetics. I personally use Amsoil full synthetic in one of my airplanes that is certified for auto gas, but it's a liquid cooled Rotax engine that prefers a motorcycle-type oil.

Sorry for the thread drift.

[Skyliner]

Absolutely nothing wrong with using diesel oil in a generator. HDEO oils have a more stout additive package and the engine will thank you for it.

All of my small engines, atvs, motorcycles and all 4 of my turbocharged vehicle engines get 5w40.


Most easily found 15w40s in chain stores are not synthetic.

Amsoil or Royal Purple are available in synthetic in 15w40 but unless you are in the desert 5w40 should serve you well at 150 hour oil change intervals.

[Springerdad]

Originally Posted by TonyD

Absolutely nothing wrong with using diesel oil in a generator. HDEO oils have a more stout additive package and the engine will thank you for it.

All of my small engines, atvs, motorcycles and all 4 of my turbocharged vehicle engines get 5w40.


Most easily found 15w40s in chain stores are not synthetic.

Amsoil or Royal Purple are available in synthetic in 15w40 but unless you are in the desert 5w40 should serve you well at 150 hour oil change intervals.

Agreed. We used to service a 'rolling office' motor coach in which the generator ran constantly. We went to Amsoil synthetic 15W40 and a bypass filter, did oil analysis, and were able to stretch oil changes to 500 hour intervals.

[BBQGUY]

From the operators manual for the HAJAx Series (5500, 6500, 7000 RV QG gensets). The oil used should meets these specifications. The OEM oil is ONANMAX 15W40. The temperature range is for the expected temperatures when you will be operating the generator. If you don't using the generator below freezing temperatures, SAE30 is the way to go. Always check your operators manual. If you don't have the 4 manuals (Operators, Installation, Parts, Service) search the web for the manual document numbers; then search here. Index of /~n0nas/manuals/onan

[nicktano]

I attached a picture of the oil recommendation section from my 2015 cummins onan 3200 manual. No mention of synthetic. The cummins facilty rep asked me why I would want to use synthetic, as if I was crazy. He said there was no benefit. Has anyone else spoken with cummins? Interested in what they were told.

[CHICKDOE]

I did contact onan about this and here is their reply.


-------------------------------
We have the following response:
-------------------------------

Thank you for contacting Cummins Onan.

Even though your manual says that it is okay to use synthetic oil we do not recommend it. We have found that it gums up the cross hatches in the cylinders. You are okay to use any brand of oil as long as it is 15w40 w/detergent.

If you have any further technical questions please call us at 574-262-4611 and ask for our in house tech.

----------------------------
Sincerely,
Cummins Onan Customer Service



at this point i'm dropping this. I ordered the onan 15w-40 and will use it. I think the key issue is to simply replace the oil per the maintenance schedule. in our case that would be once a year as it's hard to believe we will put 150 hours on the generator in a year. also, exercise it each month. I expect to be just fine.


thanks to all you have offered their experiences and advice.

[OldCoot]

Mobil 1 is the only purely synthetic oil and is available in 10-40. I use it in all internal combustion engines.

[ilmor]

Originally Posted by NMWildcat

Why? If the oil has the same specifications as the recommended I'd rather not support the manufacturers partner just because.

They don't recommend only their own oil. They provide the specs to use.

[Springerdad]

Originally Posted by OldCoot

Mobil 1 is the only purely synthetic oil and is available in 10-40. I use it in all internal combustion engines.

We should add Amsoil to that list. They DO offer semi synthetics as well as full synthetic oils.

[OldCoot]

Originally Posted by Springerdad

We should add Amsoil to that list. They DO offer semi synthetics as well as full synthetic oils.

Top 10 synthetic oils.
SO, I guess I was wrong saying Mobil 1 was the only one. I do know they were the 1st to come out with it.

Been using it exclusively since 1978.

The Best Synthetic Motor Oil (August 2016) – TopRateTEN

[Springerdad]

Originally Posted by OldCoot

Top 10 synthetic oils.
SO, I guess I was wrong saying Mobil 1 was the only one. I do know they were the 1st to come out with it.

Been using it exclusively since 1978.

The Best Synthetic Motor Oil (August 2016) – TopRateTEN

Oh I hate to say this. Actually, Amsoil was first. In fact, their tag line is "The first in synthetics" By a month or so. It was a marketing race. Mobil introduced their 5w30 shortly after Amsoil introduced their 10w40. And oh, did that Mobil 1 leak out of those engines of that era!
I worked in a Mobil station at that time, and my friend was an Amsoil dealer.
Amsoil was originally spelled Amzoil, but there was some trademark infringment, so they changed the spelling.
To that end, they are both great oils, and you can't go wrong using them.

[Skyliner]

Originally Posted by CHICKDOE

I did contact onan about this and here is their reply.


-------------------------------
We have the following response:
-------------------------------

Thank you for contacting Cummins Onan.

Even though your manual says that it is okay to use synthetic oil we do not recommend it. We have found that it gums up the cross hatches in the cylinders. You are okay to use any brand of oil as long as it is 15w40 w/detergent.

If you have any further technical questions please call us at 574-262-4611 and ask for our in house tech.

----------------------------
Sincerely,
Cummins Onan Customer Service

About the most stupid thing I have ever seen written by a customer service rep. That response is so ignorant!

How does a synthetic oil gum up cross hatches? Does the respondent even know what they are talking about?

Synthetics don't gum up anything and often run cleaner than their conventional counterparts.

If I owned an Onan, I'd use 5w40 oil which is a Group III oil anyway although the bottle says synthetic.