diesel oil viscosities for Kubota tractor

[Chris142]

My new to me Kubota tractor . Kubota says to use 10w30 below 32F and 15w40 above 32F.

Temps below 32F are pretty uncommon here. But 35-40f are common.

I'm thinking that the thing may sit weeks between being ran and that a 15w40 might not be the best choice.

Kubota does not mention 5w40.

Wouldn't a 5w40 be a better choice to use due to the fact that it's not ran every day?

 

[HemiBenny]

What’s your reasoning behind the thought that it’s not ran every day?

I would use 15w40. It’s safe to use at temps way below what you get there.

 

[Chris142]

What’s your reasoning behind the thought that it’s not ran every day?

I'm the one who will be using it . I don't plan on using it every evening after work

 

[Hohn]

Use a synthetic 15w-40 and don’t worry. I’m biased towards Valvoline, naturally, since we use thousands of gallons a week in our test facilities.

 

[NiwradND]

Rotella 15w40 full synthetic being you're in California, 5w40 if you were in a colder climate.

 

[Japanese]

Rotella 15w40 full synthetic being you're in California...

+1

 

[userfriendly]

Chevron Delo 5w40

 

[fantastic]

Wouldn't a 5w40 be a better choice to use due to the fact that it's not ran every day?

A 15w-40 synthetic would work the same. I tested the Super Tech Full Synthetic and for unused periods of time would be a good value.

 

[dnewton3]

Either 10w-30 or 15w-40 will work just fine in your area. Where I live (central IN), we see temps occasionally below zero and approaching 100F in summer. I have run both grades and not seen any significant difference in wear control.

My advice has always been this:
If your area predominantly is colder, err towards the 10w-30.
If your area is predominantly warmer, err towards the 15w-40.

But, just remember that both grades do just fine in typical tractor applications.
Pick one and overthink something else.

 

[HemiBenny]

I'm the one who will be using it . I don't plan on using it every evening after work

I meant, what’s your reasoning behind the 5w40 being better than the 15w40 since it’s not used everyday? I don’t see how that would matter. Just curious.
I should have been a little more clear with my question, I apologize.
Anyway, I still say 15w40 since you’re in a warm climate.

 

[Fabulous50s]

I run 5w-40 year round in my small Yanmar diesel engines (35HP). But I see temps well below 0F. Tractor gets plugged in, but that just warms the coolant oil is still very cold. I happened to have some Amsoil Signature Diesel, but its kind of a waste as oil will be cbaged annually with about 100 hours on it. When tye Amsoil stash runs out, ill use another synthetic 5w-40 like Delo, Delvac 1, etc.

I assume your tractor has a DPF?

 

[Chris142]

I meant, what’s your reasoning behind the 5w40 being better than the 15w40 since it’s not used everyday? I don’t see how that would matter. Just curious.
I should have been a little more clear with my question, I apologize.
Anyway, I still say 15w40 since you’re in a warm climate.

When it sits weeks without use the filter will eventually drain . Once started it will take a few seconds for the filter to fill. A few seconds without oil pressure and the 15w won't flow as fast as the 5w.

 

[oil pan 4]

My new to me Kubota tractor . Kubota says to use 10w30 below 32F and 15w40 above 32F.

Temps below 32F are pretty uncommon here. But 35-40f are common.

I'm thinking that the thing may sit weeks between being ran and that a 15w40 might not be the best choice.

Kubota does not mention 5w40.

Wouldn't a 5w40 be a better choice to use due to the fact that it's not ran every day?

If your Kubota oil never gets above 180f 30wt is fine. Every Kubota I've checked the oil was always within a few degrees of the coolant temperature.
Kubotas are pretty easy on the oil, they're one of the few diesels I'd recommend 30wt and multi hundred hour OCIs.

 

[JHZR2]

Either 10w-30 or 15w-40 will work just fine in your area. Where I live (central IN), we see temps occasionally below zero and approaching 100F in summer. I have run both grades and not seen any significant difference in wear control.

My advice has always been this:
If your area predominantly is colder, err towards the 10w-30.
If your area is predominantly warmer, err towards the 15w-40.

But, just remember that both grades do just fine in typical tractor applications.
Pick one and overthink something else.

Curious - do you own a Kubota, and 15w-40 is in the options your FSM prescribes?

Our severe service diesel genset in the Caribbean is a Kubota and recommends straight or 10w- grades:

Usually it’s 70-90F at startup which may be aligned to OP’s climate. We run straight, but I’d rather run 15w-40 HDEO I think.

We run delo, thousands and thousands of hours after hurricanes.

 

[CleverUserName]

You could use both. 50/50 blend of 10w30 and 15w40, just make sure you use the same oil brand and type so you don’t get any surprises.

I’ve done this before and had a VOA done. The viscosity was within 2% of what the Widman calculator predicted.

 

[38Chevy454]

I use Delo synthetic 5W-40 in my Kubota tractor. Also same oil in the Cummins ISL9 engine and the Kubota generator in my motorhome. Keeps it simple. Even better I bought a bunch on clearance sale last year for around $9/gal.

 

[oil pan 4]

Curious - do you own a Kubota, and 15w-40 is in the options your FSM prescribes?

Our severe service diesel genset in the Caribbean is a Kubota and recommends straight or 10w- grades:

View attachment 319271

Usually it’s 70-90F at startup which may be aligned to OP’s climate. We run straight, but I’d rather run 15w-40 HDEO I think.

We run delo, thousands and thousands of hours after hurricanes.


View attachment 319272

In the Caribbean Mon I would just say use straight 30wt. No need for a multi grade if it never gets anywhere near freezing.

 

[JHZR2]

In the Caribbean Mon I would just say use straight 30wt. No need for a multi grade if it never gets anywhere near freezing.

No kidding but for a genset that starts and loads rapidly I kind of would prefer more developed flow, and given that it loads continuously for long times, the 40wt I like as well.

That said, I was really just more curious because @dnewton3 made the recommendation that isn’t the same as our manual, and it made me wonder how much it varied by engine class or use case with Kubota.

 

[dnewton3]

I have two Kubota tractors; L3430GST (about 1000 hours) and L3830GST (about 1200 hours). The manual states 10w-30 or 10w-40 for pretty much any environmental temps. API CD or higher ... so, anything modern will suffice quite well.

I recommend 15w-40 for warmer climes simply because it is FAR more common (and therefore cheaper) than 10w-40 diesel rated lubes. I would use 15w-40 in any application for a Kubota that saw low temps around 20F or above. I see no benefit to seeking out a 10w-40 when 15w-40 is every bit as capable and just easier and cheaper to get. Why Kubota doesn't step into the modern era and recommend 15w-40 is beyond anyone's guess ... I guess old habits die hard.

 

[Plumb Bob]

Why Kubota doesn't step into the modern era and recommend 15w-40 is beyond anyone's guess ... I guess old habits die hard.

Beta Marine, a marinized Kubota goes even further,

Engine Oil​

Engine oil quality should have the minimum properties of the American Petroleum Institute “API” classification CF with multi-grade SAE ratings as listed in the following table.

NB: An acceptable alternative is a mineral based, semi-synthetic lubricating oil with a content mix no greater than 30% being synthetic based. Do not mix two different types of oil or SAE rating.

Do not use lubricant additives and/or fully synthetic lubricating oil.