1985 Onan B43 engine, which oil?

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I have said engine in my garden tractor, which is used as a garden tractor, not mowing. It is a mostly pressure lubed engine (rear cam bearing is splash, valvetrain is splash). Manual calls for oil ranging from 5w20 for -20F to 20F to SAE30 for summer use; 30F and higher.

Engine is older, but just tore it down for valve job and new rings. All other parts within original wear specs.

Of course, this is a flathead engine, flat tappets.

There is NO OIL FILTER on this engine, oil changed every 25 hours.

In the winter I have been using synthetic 10W30. I have been using JD Torq-Guard 30wt in summer.

Should I change what I am doing, or is this a good schedule? Oh, I live in MN, so it gets COLD, and the tractor is just in a shed, no heat, but I am installing a silicon heater to the oil pan.

Thanks in advance!
 
Welcome to BITOG!

You can use one oil year-round. On your short 25 hour intervals, it'll never be in there long enough to shear. For an engine without a filter, I wouldn't go beyond that. 25 hours is what my mower and snowblower get.

I used to live in a very cold part of New York State; my snowblower would see startups in -20F every winter and -30F a few times. Castrol Edge 0w-30 was my choice. That's my recommendation for you as well. It's sufficiently stout to protect your older Onan engine.

There are plenty of other choices too.

Rotella T6 5w-40
Castrol 0w-40
Mobil 1 0w-40
Mobil 1TDT 5w-40
Delo 5w-40
 
Originally Posted By: Rat_Patrol
I have said engine in my garden tractor, which is used as a garden tractor, not mowing. It is a mostly pressure lubed engine (rear cam bearing is splash, valvetrain is splash). Manual calls for oil ranging from 5w20 for -20F to 20F to SAE30 for summer use; 30F and higher.

Engine is older, but just tore it down for valve job and new rings. All other parts within original wear specs.

Of course, this is a flathead engine, flat tappets.

There is NO OIL FILTER on this engine, oil changed every 25 hours.

In the winter I have been using synthetic 10W30. I have been using JD Torq-Guard 30wt in summer.

Should I change what I am doing, or is this a good schedule? Oh, I live in MN, so it gets COLD, and the tractor is just in a shed, no heat, but I am installing a silicon heater to the oil pan.

Thanks in advance!


B43 should have a filter. I assume a 318.
 
Originally Posted By: Ramblejam
B43/B48 were both available with, or without an oil filter.


Yep have a 316- ONAN without oil filter
and a 318 - ONAN with oil filter.
 
Its the 316, no filter. And my Onan does not have the simple plate over the fuel filter adapter unfortunately.
 
So the JD 10w-30 (looks like dino oil) would be better than an automotive type full synthetic 10w-30? For the 2-3 oil changes a year @ 1.5 quarts, a couple extra bucks per quart won't break the bank by any means for the better stuff.
 
Nobody here would recommend 10w-30 in a gasoline car engine when the temperatures are well below zero. I don't believe you should be using it in your tractor either. Things have improved since 1985. Even John Deere recommends their 0w oil for extremely cold temperatures.
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Source
When I was living in a very cold climate, the difference starting my snowblower with 0w-30 was significant. Use it in the summer too, if you'd prefer. Or, switch back during the warmer months.
 
A few things...

1. The calculator is not accurate at these temps. Want an example?

Using Mobil 1 0w-30 values, the calculator has an operational viscosity of 23994 @ -40°C. Convert kinematic viscosity to dynamic viscosity by multiplying the density (0.842) results in 20203 @ -40°C. The actual listed MRV @ -40ºC is 13250. That's a huge difference.

2. Even if it were accurate, the actual measurement itself (kinematic viscosity) should not be used to compare cold-temp performance; this is why SAE J300 (which governs viscometrics) uses CCS & MRV values to dilenate between the grades.

3. The engine in question is a flat-head Onan, without an oil filter, running a pan heater. If a different engine architecture was being discussed, or he didn't have a heater, then I'd feel differently about things. My only real concern is the battery, but as long as he has a temperature-compensated automatic charger, it'll be good to go.
 
1. If the calculator's inaccurate, do the calculations how you see fit and show how you got to that result. Just saying wrong without offering a solution isn't appropriate.

2. If you feel cSt is inappropriate, show us the proper data at -20°F so we can compare.

3. What about his Onan's architecture makes it less-susceptible to startup wear than other OPE? He doesn't yet have a pan heater. There may also be times when he can't or doesn't use it.

What about the 10w-30 makes it better-suited for this application than something designed for cold weather use?

Why should we ignore John Deere's advice here too?

Originally Posted By: Ramblejam
As thin as possible; as thick as necessary

Does this only apply when it benefits your argument?
 
For an old splash lubricated flat-head... 10W-30/40 is fine. What temps to you expect to encounter? The only downside to going thinner (0/5W-)might be increased consumption, but you won't know till you try.
 
Originally Posted By: bmwpowere36m3
For an old splash lubricated flat-head... 10W-30/40 is fine. What temps to you expect to encounter? The only downside to going thinner (0/5W-)might be increased consumption, but you won't know till you try.


I have no issues changing oil with temps, but in summer I will experience from about 50-100 degrees F. Winter can get down to -20, I try not to be outside when it gets that cold though!
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Originally Posted By: Rat_Patrol
Its the 316, no filter. And my Onan does not have the simple plate over the fuel filter adapter unfortunately.


Interesting. I think the P218g all had filters. I just assumed the B43 did also.
 
Originally Posted By: jhellwig
Originally Posted By: Rat_Patrol
Its the 316, no filter. And my Onan does not have the simple plate over the fuel filter adapter unfortunately.


Interesting. I think the P218g all had filters. I just assumed the B43 did also.


Yeah, JD was able to save probably $50 not having the filter, and since the 316 was meant as a more budget friendly tractor, they chose to save the $$ instead of the engine.

I've thought about tapping 2 holes in the oil pan and running a pump and filter, but it lasted 30 years the way it is, it should get me a few more until I upgrade to a P series or something.
 
Ran the 316 on 20w50 for over 15 years 8-12 hours a day mowing full throttle usually around 20 hours per weekend.. sometimes it would even bog down with wet 15" Field Grass.

Now I use 15w40 in it.

I wouldnt go back to 30wt but its been an abused tractor... I also dont use the tractors in the middle of winter.

Much less mowing now. you can mow for 5-6 hours without adding oil. I dont expect more out of several thousand hour beat on onan.

In your case I think you could make a strong case for 0w30,0w40,5w30 full syn
straight 30wt or 15w40 mixed fleet oils in the summer etc.

They arent that picky just have the right oil in them for the right temps.
 
Originally Posted By: jhellwig
I'd run straight 30wt in it. That has the least consumption in my 318 with the p218. It likes to drink multi weights.

Straight 30 in a Minnesota winter for splash lubrication? I don't imagine there'll be a lot of splashing going on.

John Deere's chart is correct. Use their 0w-40 if you want a JD product, or a 0w-30/0w-40 from wherever you buy oil. At 25 hour intervals, there's no reason not to.
 
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