11.5kW diesel generator - oil recommendation?

[ADKgenset]

Hello,

I have an 11.5kW diesel (Onan DNAD) genset that powers a small cabin. Made 2004-ish, has 7500 hours on it. I change the oil pretty religiously at intervals less than the 250 hours the manual calls for.

I normally run 10w30 oil in winter, but have slow start ups when it gets real cold (10F to below zero). This is with using blended diesel (50-50).

The manual calls for 5w30 oil below zero, so planning to switch to that - but having a hard time finding something.

I’ve attached the relevant section from the manual. I find 5w30 Rotella T6 that may work, but Cummins says not to use fully synthetic oil. Anyone able to point me in the right direction? Is synthetic actually an issue for this genset? I’m fairly clueless as to API classes, backward compatibility, etc.

Any help is appreciated!

 

[CalG]

Oil is oil

Get over it!

the 0w- XX is all the rage these days, as it goes along with the greenie weenie agenda. So what your engine "won't last as long",

Longer than WHAT?

How long do you plan to live? And if a rebuild is needed, it's small money!

Do you think the lubrication "scientists" have been fiddling their thumbs since Cummins wrote their manual?

Get that engine going!

 

[RjCorazza]

You don't mention any summer ambient temps, but IF you want to stay within Cummins' viscosity recommendations, they are not recommending 5w30 above 50 degrees f.
I personally would use a 5w40, or 0w40 synthetic. If you're concerned about the "no synthetic" thing, I would investigate the source and timeframe of that information.

 

[ADKgenset]

Ha! Good stuff, thanks guys. Great info on this site.

I'm a rookie here - what's the knock on synthetic? CalG, your point about advances in oil since 2004 make a lot of sense to me. Not sure why they'd suggest not to use synthetic, but that's about all I can find that's 5w30 diesel oil.

RjCorazza - I'd have an oil change back to 10w30 or 15w40 before we get back above 50 in my area.

 

[DarkBlack]

7,500 hours on a small engine is pretty impressive. Your oil choice has worked for 20 years. Why change now? Did it used to start easy below freezing? If so, what’s changed?
My guess is , the manual states , they “don’t recommend synthetic.” That’s a different meaning than “don’t use synthetic “.
They also spec CH, which was current at the time. You’ll be buying CK with a back spec to CH.
Can you externally warm the engine before starting when it’s really cold?

 

[RandyT]

Ha! Good stuff, thanks guys. Great info on this site.

I'm a rookie here - what's the knock on synthetic? CalG, your point about advances in oil since 2004 make a lot of sense to me. Not sure why they'd suggest not to use synthetic, but that's about all I can find that's 5w30 diesel oil.

RjCorazza - I'd have an oil change back to 10w30 or 15w40 before we get back above 50 in my area.

Not so much a knock on synthetics as back in 2004 synthetics were just becoming known and most engine manufacturers didn't trust them and recommended not using synthetics. Then as they started becoming more well known they started saying you can use synthetics but don't use them for the first 50-100 hours because they are so slick they will prevent proper ring seating. Now most engine manufacturers now offer full synthetic in their own brand, and some don't even offer a Dino version.

 

[ADKgenset]

Not so much a knock on synthetics as back in 2004 synthetics were just becoming known and most engine manufacturers didn't trust them and recommended not using synthetics. Then as they started becoming more well known they started saying you can use synthetics but don't use them for the first 50-100 hours because they are so slick they will prevent proper ring seating. Now most engine manufacturers now offer full synthetic in their own brand, and some don't even offer a Dino version.

The "no fully synthetic" actually came from a Cummins service rep, which surprised me since the manual only specified viscosity and API rating. But as you said maybe synthetics weren't much of a consideration at the time it was manufactured.

7,500 hours on a small engine is pretty impressive. Your oil choice has worked for 20 years. Why change now? Did it used to start easy below freezing? If so, what’s changed?
My guess is , the manual states , they “don’t recommend synthetic.” That’s a different meaning than “don’t use synthetic “.
They also spec CH, which was current at the time. You’ll be buying CK with a back spec to CH.
Can you externally warm the engine before starting when it’s really cold?

Good question. I don't have a way of externally warming, at the moment.
It has never started well below freezing, no. I've only addressed it through a steeper kero:diesel mix (was told by the guy who serviced for me that we could go up to full kero, but have never been empty when it's time for the winter kero fill so we normally end up about 50:50). It's not uncommon to have gelling issues, or what I assumed were gelling issues. Generator powering the cabin, then it shuts down on a real cold night. I'd normally add Diesel 911, change fuel filters, and hope for the best. After looking through the manual, began to think maybe going down to 5w30 would help at least with the slow cold starts, since I've never put that in and the manual recommended it for the sub zero temps. (That thinking may be off base, I'm fairly clueless).

Maybe at 7500 hrs I should spend more time thinking about how to save for when this machine kicks the bucket

 

[RandyT]

The "no fully synthetic" actually came from a Cummins service rep, which surprised me since the manual only specified viscosity and API rating. But as you said maybe synthetics weren't much of a consideration at the time it was manufactured.

Here is the answer to the Cummons full synthetic directly from their own website..

https://shop.cummins.com/SC/product/valvoline-premium-blue-extreme-full-synthetic-engine-oil-5w40-1-gal-c774038ga/01t4N0000048ZYPQA2

 

[nyone]

Have you looked at other issues that may be causing hard cold starting like glow plugs or water in fuel?

Generaly diesel engines dont like starting in the cold.

Is it slow crank or long crank?

 

[nyone]

.

Maybe at 7500 hrs I should spend more time thinking about how to save for when this machine kicks the bucket

You are nearing the end of that units life. Also at 0.4gal/hr and $3gal for fuel you have spent $9k on fuel. Ever think about putting solar in?