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?

 

[3930dave]

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.


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

On the rating story, C_ diesel-oil is fairly straight-forward (vs. the newer classes), and are backwards-compatible.

Oil Categories

On air-cooled applications, there can be a case for Conventional, but I'm guessing that your Onan is water-cooled (?).

Wide-range synth (like T6) are OK by me, but for specialty options, I often end up checking Amsoil.... may be a dealer near you, or they do ship.

Sounds like your biggest problem is staying-Running @ ColdNight.... I'd be tempted to look at something like a fuel-bowl warmer, and see if that makes a difference (infra-red heat lamp, if nothing else, if you can safely position and secure one.... or even just a regular incandescent 100w PAR30 bulb - making up a small cage around it with rodent-grid wire (Home Depot, etc) is one way to prevent direct (fire) contact with the bulb surface).

I regularly treat diesel with Stanadyne Performance..... that, or equivalent, can help improve Cetane, and manage water-issues.

Rgds, D.

 

[LouNY]

I'd simply switch the oil to a quality synthetic 5W-40 for year round use.
As far as it gelling after you get it started, a shroud with a simple thermostatic control to keep it warmer in cold weather would stop that or add some heat pads to the fuel filters.

 

[Chilliwack Murray]

Outside of break-in issues, the main issue with the early synthetics was seal and gasket leaks. The materials used at the time would not contain synthetic oil and some soft parts were damaged by some of the synthetic oils. You should have no issue using any of the mainstream synthetic blends available today but that unit won't really benefit from the top of the line synthetics vs a blend for half the money, just stay within the viscosity range specified. That unit has a Lister-Petter engine and you will find a lot more info on the Listerengine forum since that's their 'thing'. I would go with the Lister Petter specs rather than the Cummins owners manual as Cummins documentation will lean toward what Cummins has available as long as it will work, but not necessarily the best choice.

If I recall correctly, the glow plugs weren't connected on these gensets originally as they were built for emergency standby and were intended to have a block heater to maintain the engine around 130F. (no time for glow plugs when you have to be supplying power in 15 seconds). Check if there is a wire on the glow plugs, and if it actually goes anywhere. If not, hook them up to a momentary pushbutton switch rated for the current and that will help starting immensely, and as a bonus you have brand new glow plugs.

Those were fairly reliable standby units but prone to leaks and carbon buildup that could damage pistons and injectors. The few I saw with high hours needed regular valve adjustments. At 7500 hours you are probably 3/4 through its life. If you can find a Kubota powered unit to replace it, they will run 30,000 hours with just regular maintenance and I've seen them run well over 50,000 hours with no major repairs.

 

[Mike1955]

ADK your original post was about oil, I think. My preferred brand although I don’t always have it is Amsoil. I think it would serve you well to. Viscosity is something you may just need to change for. I enjoy the extended change intervals too.

 

[big bubba]

welcome to forum. have you inquired directly w/Onan as to their current recommendations? regards