Straight 30 or 15W40 for hard use air cooled small engine?

[z71bill]

Bot did I go down the rabbit hole on this thread!

I have a Champion 8750w Portable generator, currently it has Kirkland Synthetic 5W-30 in it, for no other reason than my F150, Big generator and mower are also running 5W-30 (Well, apart from when I put 5W-20 in by accident) so I can stock a single weight of oil and use it everything

The book says recommended 10W-30, but 5W-30 Synthetic is on the chart. I am in Houston, TX.

View attachment 215608

The generator is stored in my detached garage which should never get below freezing during a winter storm (If it drops below freezing, I will heat it)

The generator is a backup to my Generac RG027-QS, and could be used during a hurricane or possibly another winter storm. Seems to me that 5W-30 is a good oil choice, but after reading this thread I am not so sure.

The generator would not be loaded to max for extended runtimes, and it does have an eco mode to lower the RPM.

Should I maybe switch to 10W-40? Or 5W-40? Any other suggestions welcome

For what ever its worth --

When I store my generator it usually has fresh 5W30 in it.

If the next time I need it it is 12 degrees outside I am good to go and I will run it for 10-15 hours and then before it gets dark change it. using 5W30 or 10W30.

But the oil I fill it with will be stored inside - and since the engine is warm it will start right up


If the next time I need the generator it is 98 degrees outside I am still good to go - I will run it 5 - 10 hours then change it to straight 30 or 15W40 -

This way I have flexibility - no matter what the outside temp is I can handle it.

 

[#18FAN]

For what ever its worth --

When I store my generator it usually has fresh 5W30 in it.

If the next time I need it it is 12 degrees outside I am good to go and I will run it for 10-15 hours and then before it gets dark change it. using 5W30 or 10W30.

But the oil I fill it with will be stored inside - and since the engine is warm it will start right up


If the next time I need the generator it is 98 degrees outside I am still good to go - I will run it 5 - 10 hours then change it to straight 30 or 15W40 -

This way I have flexibility - no matter what the outside temp is I can handle it.

Why not just run a 5w40 or am I missing something seems like a no brainer.

 

[4WD]

Why not just run a 5w40 or am I missing something seems like a no brainer.

I now have Delvac 1 5W40 in three pull starts - and Redline 10W30 in my electric start ...

 

[4WD]

I wonder if the engines are getting low on oil and the small amount of oil is getting too contaminated to lube properly?

Wonder if a low Noack is not helpful?

 

[The_Eric]

I use the Rotella because it has zinc, which my old vintage engines need. And because when my brother worked for New Holland, they ran tests on this diesel rated oil and found it to be very good. I plan on contacting Shell and see what they say.
Thoughts?

I really doubt that you NEED the added zinc. Yes it's an old engine with flat tappets, but most newer engines run that design too. The thing is that there is next to no spring pressure, unlike in older cars or high performance applications and it it really doesn't require anything special. That said running an oil with a robust anti-wear add pack is certainly not gonna hurt, so if it makes you feel better, then you absolutely should. Heck I do similar things too.

 

[z71bill]

Why not just run a 5w40 or am I missing something seems like a no brainer.

Because 5W30 is better than 5W40 when it is below freezing and 15W40 is better than 5W40 when it is hot out.

And both cost way less than 5W40!

 

[#18FAN]

Because 5W30 is better than 5W40 when it is below freezing and 15W40 is better than 5W40 when it is hot out.

And both cost way less than 5W40!

How so?

 

[z71bill]

How so?

My opinion - based on my research and experience. 5W30, straight 30 and 15W40 is what I use - depending on outside temp.

Using a 5W40 when it is over 100 degrees has no advantage over a 15W40.

Running a 5W40 when it is 10 degrees has no advantage over 5w30.

Between 50 and 90 hard to beat a straight 30.

I can buy 5W30, SAE 30 and 15W40 for $11-$17 a gallon. What is the best deal on 5W40?

I do have a gallon of 5W40 that I grabbed on clearance - so I would use it. Just not my first choice.

 

[Astro_Guy]

How so?

See https://oil-club.de/wcf/index.php?attachment/15338-sae-j300-hths-basisöle-pdf/ and note that back in the day a 5w-40 was required to have a minimum HTHS viscosity of 2.9 vs 3.7 for a 15w-40. That was a big difference. Today (after 2007) a 5w-40 is required to have a minimum HTHS viscosity of 3.5 vs 3.7 for a 15w-40. It's a smaller difference but possibly a very important one when running at high loads in high ambient temperatures.

To your original point, there is probably little difference to be seen when running at moderate loads at comfortable outdoor temperatures. Personally I run 15w-40 Rotella T6 in the lawn tractor that can run for an hour in higher temperatures. My generators run 5w-40 Rotella T6 and most everything else runs 10w-30 Mobil1 HM. Back when Mobil was more forthcoming with specification their synthetic 10w-30 high mileage had a 3.5 HTHS viscosity. This may or may not be the same today. If confronted with an extended power outage with temperatures above 90 I might put 15w-40 in the generators. Aside from that it will be synthetic 10w-30 or synthetic 5w-40 HDEO in my OPE.