Oil for Onan 4000 Generator

[High Road Travelers]

In my Onan gas 7000 generator I use the proper oil as stated in the Owners Manual.
I usually operate in temperatures ranging from 10 to 100 degrees, so I use 15W-40 oil, as the manual and Onan states. It normally states "diesel" on the bottle, but can be used in anything needing 15W-40 oil.
I could use 30 weight oil (not 10W-30, just 30), as it is good for temperatures over 100 degrees, and sometimes I drive in those conditions also. But 10 degrees one way or the other is not going to end the world.
There are two other oil weights that can be used in the generator per Onan, but they are used in extreme cold conditions, zero or less degrees; and I am not going to camp in those conditions.
So 15W-40 it is. Any good brand will do for me.
Thanks,

[AITG]

I have a case of Kendall Super D XA 15W-40 left over from my Duramax pickup. I take oil samples at every change and engine wear is virtually non-existent. Given the low capacity of the 4000 crankcase four gallons should be a lifetime supply.

The most important thing is to keep it full. There isn't much reserve capacity there.

[norrirn]

Originally Posted by hpdrver

I thought I was ordering the right oil to do an oil change. I thought I should use Onan max 15w40. However when I received the oil, it states on the bottle it is for diesel. Is this the correct oil for the gas Onan 4000. Thanks

The manual for my Onan 4000 specifies SAE 30.

[PeterFTH]

I always use Shell Rotella T 15/40 in my diesels ... I might mention that many Goodyear Tire and Maintenance operations offer oil/filter changes for RVs - not all do - you should call ahead. If they have a lane with a pit, they probably will. Many are in truck stops - Pilot, Flying J etc ... For about $200 maybe plus a few dollars they do my Cummins 8.8 400HP ISL change of 7 gallons oil, filter, fuel water separator, full chassis inspection and lube. You can't beat it with a stick.

[THenne1713]

A few extra thoughts: 1) NOT all 15w40 diesel oils (are NOT suitable/ are NOT rated) for the Onan air-cooled gasoline GEN; if it does NOT have a "S" rating (spark engine), it is not suitable, in opinion of GEN MFR and OIL MFR, and there are MANY without the "S"(spark engine) rating; 2) I FAIL to understand willingness to pay $15/QT for any OIL that is no better than MANY, MANY $3/QT Brand Name Oils, Petro or SYN based, and 3) FAIL to understand paying $25/gal for any canned FUEL/OIL MIX (e.g. 40:1/50:1 mix for chainsaw/ blowers, etc), but do agree (Maybe?) suitable for "winter storage without moisture", using a few ounces in each engine/ tool? (MY Use of oil mix fuel is usually 1/2 to 1-gallon/day for blower/ weed eater, but esp. when running chainsaw)

[Shell Man]

Ok. I'm going to try to make this brief. I was in the motor oil industry for 30+ years. First,Onan doesn't make their own oil. They put out the specs and have it produced from an oil company and put their label on it. If you have a gas generator you should most likely use a 10w-30. Truthfully, single weight oils are obsolete. Diesels generally require a 15w-40, or if you want to use a synthetic, a 5w-40. I use Rotella synthetic 5w-40 in my Onan 8k. Lastly, I would never use any additional additives. Think of it this way- motor oil companies blend a product to exact specifications for specific manufacturers requirements. Adding an additive actually dilutes the balance of the additives already in the motor oil. Hope this helps.

[Mudfrog]

Originally Posted by Shell Man

Ok. I'm going to try to make this brief. I was in the motor oil industry for 30+ years. First,Onan doesn't make their own oil. They put out the specs and have it produced from an oil company and put their label on it. If you have a gas generator you should most likely use a 10w-30. Truthfully, single weight oils are obsolete. Diesels generally require a 15w-40, or if you want to use a synthetic, a 5w-40. I use Rotella synthetic 5w-40 in my Onan 8k. Lastly, I would never use any additional additives. Think of it this way- motor oil companies blend a product to exact specifications for specific manufacturers requirements. Adding an additive actually dilutes the balance of the additives already in the motor oil. Hope this helps.

Well, my Onan manual specifically states that 10W-30 is a good oil to use,,, if the ambient air temperature stays below 80°F. That would not be the best oil to use where a lot of us folks RV.

Of course, Onan may have changed their spec ratings since my 19 year old was manufactured. For now though, I'll keep going with the straight 30 weight that my manual states is best to cover the range of temperatures routinely encountered in my area.

[richardkronz]

Originally Posted by Mudfrog

Well, my Onan manual specifically states that 10W-30 is a good oil to use,,, if the ambient air temperature stays below 80°F. That would not be the best oil to use where a lot of us folks RV.

Of course, Onan may have changed their spec ratings since my 19 year old was manufactured. For now though, I'll keep going with the straight 30 weight that my manual states is best to cover the range of temperatures routinely encountered in my area.

Amsoil makes an oil specifically for air-cooled engines which is what my Onan is. I use it in everything from lawn mowers to generators and other small engines and it works very well. It is a 10 W 30 / 30 weight oil.

[tetranz]

For what it's worth, I got this for my generator. It seemed pretty good value for oil, fuel filter, air filter and spark plug.

https://amazon.com/gp/product/B07QH7W647

[High Road Travelers]

Originally Posted by Mudfrog

Well, my Onan manual specifically states that 10W-30 is a good oil to use,,, if the ambient air temperature stays below 80°F. That would not be the best oil to use where a lot of us folks RV.

Of course, Onan may have changed their spec ratings since my 19 year old was manufactured. For now though, I'll keep going with the straight 30 weight that my manual states is best to cover the range of temperatures routinely encountered in my area.

I'm with you Mudfrog; I use what the manual specifically states, thinking that whoever makes a piece of equipment knows more about it than anyone else.
Your 19 year old spec is still correct; you evidently run in a cooler climate than myself though. We will be over 80 degrees for a few days here so I'll keep my 15W-40.
Thanks,

[ga traveler]

Originally Posted by richardkronz

Amsoil makes an oil specifically for air-cooled engines which is what my Onan is. I use it in everything from lawn mowers to generators and other small engines and it works very well. It is a 10 W 30 / 30 weight oil.

10 W 30 is a 10 weight oil. w means winter and 30 means it has additives to protect like a 30 wt oil.
All multi grade oils are the weight (viscosity) of the first number. The second number is the ability to protect like that wt oil.
In other 10W30 is 10 wt oil period. 10W40 is 10 wt period. 20W30 is a 20 wt period. 15W45 is a 15 wt period

[fatboy4909]

The attachment is the Safety Data Sheet for the Onamax SAE 15W40 Engine Oil from Ashland. It does specify a zinc content of just under 2%.

[Randalpho]

Originally Posted by Shell Man

Ok. I'm going to try to make this brief. I was in the motor oil industry for 30+ years. Lastly, I would never use any additional additives. Think of it this way- motor oil companies blend a product to exact specifications for specific manufacturers requirements. Adding an additive actually dilutes the balance of the additives already in the motor oil. Hope this helps.

Shell Man,

I was very curious on your input on the lowering of ZDDP in modern oils and using it in older flat tappet engines. ZDDP was lowered by the EPA due to harming catalytic converters and Diesel Particulate Filters. I'm currently using Valvoline VR1 20w50 racing oil in my 1977 GMC pickup for the higher ZDDP. I'm currently using a conventional 30W oil in my 1999 Onan 5.5BGM.

Neither engines have a catalytic converter and both have flat tappets. There are plenty of ZDDP additives on the market but is it really needed using modern oils?

[EdInArk]

Originally Posted by hpdrver

To answer what speciations are on label; here they are

Meets APIServices CK-4,CJ-4,CI-4,CI-4 PLUS,CI-4,CH-4/SN

In my opinion the SN at the end covers it. I'd use it.

Originally Posted by norrirn

The manual for my Onan 4000 specifies SAE 30.

The manual I downloaded from Onan says 15w40 is fine, though, of course, they recommend their own oil