5W-40 or 15W-40 Full Synthetic

[ct12555]

Please excuse me if this topic has been covered. I did a search and could not find an exact answer to my questions.

I have several small engines (Briggs and Honda) on various OPE, including 2 push mowers, a generator, a log splitter, a power washer and a Ferris zero turn with a 26 HP Briggs. I live in east Texas with summer highs sometimes up to 105+ and winter lows very occasionally in the low teens. Other than the log splitter (and maybe generator) most use comes in the warm and hot months.

Could I get by year round with full synthetic Rotella 5W-40 for all the above applications? Are there application where full synthetic 15W-40 would serve me better than the 5W-40? Also, if I am misunderstanding and neither is a good choice, that knowledge would also be appreciated.

Thank you in advance for any help. This is one of those topics where I am pretty ignorant.

 

[CT8]

These days the main thing is the syns are better for starts well below 0*f. And in some instances pushing the oil change intervals. Either way pick one and be happy oils these days are that good. To add there possibly may be more consumption with a 5w oil but just keep an eye on the oil level.

 

[JimPghPA]

Google "motor oil chart temperature degrees Fahrenheit" and click on the black and white chart on the right side.

20W is good down to 23 degrees F.

15W is good down to 14 degrees F.

5W is good down to -13 degrees F.

 

[BrocLuno]

Yeah, but ...

5W-40 Rotella T6 is all over Wally World at reasonable prices. So you don't need the 5W, it won't hurt anything and might help with the splash lubed motors getting splashed a little better as they warm up

I'm looking at going this way too for now. I could live with straight SAE 30HD because it does not get that cold here either. But finding a good premium SAE 30HD is a ton harder than finding a 2.5 gallon jug of T6 on the average day. So being lazy, and not wanting to order a drum of oil while we go through the next round of oil formula changes (HDEO -> CK...), I'm just splashing T6 in most everything for now.

The motors are all happy so far

 

[JimPghPA]

By 5W I meant 5W-40 or 5W-50.

 

[JimPghPA]

Castrol 10W-50 Synthetic 4T Motorcycle oil would be an ideal choice for the temperature range you see in Texas.

10W is good down to 5 degrees F. and at the high end 50 is good beyond 122 degrees F.

 

[JimPghPA]

For the temperatures you see in Texas, in the equipment that does not get used in the winter, I would run Mobil 15W-50 or Mobil V-twin 20W-50 motorcycle oil.

For equipment that could see your winter temperatures or the hot summer temperatures, I would run Castrol 10W-50 Synthetic 4T Motorcycle oil.

 

[ShotGun429]

JimPghPA says:For the temperatures you see in Texas, in the equipment that does not get used in the winter, I would run Mobil 15W-50 or Mobil V-twin 20W-50 motorcycle oil.
And I couldnt agree more!! Sumps on my power equipment reach 300 degrees F on hot days with hard use.

 

[ct12555]

Thank you all very much for your responses. You have given me much to think about and greatly helped my understanding. However, I am still confused about about one thing, based on JimPghPa's information above. Comparing two oils such as 5W-40 and 15W-40, it is my understanding that they offer exactly the same protection at higher temperatures, but the 5W offers protection all the way down to -13, while the 15W is good to only 14. Because of the wider temperature range, why would the 5W not always be the choice between these two? Is the additional consumption, mentioned by CT8, the only reason?

PS I am now leaning heavily toward the 10W and 15W-50.

 

[HerrStig]

My Briggs splash lube genset gets T6 and doesn't burn any. The 5W performance makes it very easy to pull start in cold weather, a practical test at 4 degrees in my case.

 

[Astro_Guy]

You really do not need an SAE 50 oil for your application. The xw50 oils discussed in this thread are for motorcycles that will regularly rev to over 6000 RPMs. Your OPE should never exceed 3600 RPMs, with that figure being specific to small generators. An SAE 40 oil is more than you should ever need.

On the practical side of things, it will be easier to pull the cord on a recoil start motor with 5w40 than with 15w40 in cold weather. I ran a leaf vacuum / chipper / shredder with 4.5 HP Tecumseh for 15 years on straight SAE 30 dino oil. I was amazed at how easily this machine started last year after switching to T6 5w40.

That being said, I am switching over to Rotella T5 15w40 this season due to the oil consumption issues wit this machine, We'll see how it goes. Your mileage may vary.

 

[JimPghPA]

Originally Posted By: Astro_Guy
You really do not need an SAE 50 oil for your application. The xw50 oils discussed in this thread are for motorcycles that will regularly rev to over 6000 RPMs. Your OPE should never exceed 3600 RPMs, with that figure being specific to small generators. An SAE 40 oil is more than you should ever need.

On the practical side of things, it will be easier to pull the cord on a recoil start motor with 5w40 than with 15w40 in cold weather. I ran a leaf vacuum / chipper / shredder with 4.5 HP Tecumseh for 15 years on straight SAE 30 dino oil. I was amazed at how easily this machine started last year after switching to T6 5w40.

That being said, I am switching over to Rotella T5 15w40 this season due to the oil consumption issues wit this machine, We'll see how it goes. Your mileage may vary.


It's not about the RPMs, it is about the fact that these are air cooled engines that can be used when the ambient temperature can be greater than 100 degrees Fahrenheit. The 50 weight will give the needed protection in air cooled engines when things are that hot.

Here on BITOG Cujet in Florida swears by Mobil 15W-50 in all of his outdoor power equipment. He even wrote about losing a few motors on hot days before he started using Mobil 15W-50.

If you can't find Mobil 15W-50 then look for Mobil V-twin 20W-50 motorcycle oil.

 

[JimPghPA]

BTW, Cujet also wrote about people losing engines by running them too close to a building because when they are too close to a wall they do not get enough air flow and end up recycling some of the hot air they are putting off. So do not run you engines next to any walls.

 

[JimPghPA]

Originally Posted By: ct12555
Thank you all very much for your responses. You have given me much to think about and greatly helped my understanding. However, I am still confused about about one thing, based on JimPghPa's information above. Comparing two oils such as 5W-40 and 15W-40, it is my understanding that they offer exactly the same protection at higher temperatures, but the 5W offers protection all the way down to -13, while the 15W is good to only 14. Because of the wider temperature range, why would the 5W not always be the choice between these two? Is the additional consumption, mentioned by CT8, the only reason?

PS I am now leaning heavily toward the 10W and 15W-50.


One of the reasons people use oil with a lower spread between the two numbers is that depending on how good of a job the oil manufacturer did in making the oil, there can be a tendency for oils with a wider spread to sheer (break down to a thinner oil). So an oil with less spread is a little less likely to sheer.

 

[JimPghPA]

BTW, if we were talking about engines with a radiator and water cooling system then the thicker (50 weight) oil would not be needed.

 

[Killer223]

wow... the range of responses, yes the 5-40 retella T6 would be great option and serve all those engines just fine.
heck i use tractor supply 15-40 in all mine. and still no issues. and it snows here!!!!

 

[TiredTrucker]

Causes me to wonder how many of us do just fine on a 10w30 even in 100+F heat and rack up thousands of hours on our air cooled OPE stuff. I have a portable generator that only gets 10w30 year round and has to operate on my semi truck from -20F up to over 100F, and it does so mounted inside a custom box mounted on the frame rail of the truck, that has a couple of panels I remove when using the generator. It runs right inside the box (keeping it out of weather and for security) for up to 10 hrs at a stretch. Taken a couple of JD riders, mowing 2.25 acres at a shot, to upwards of 5000 hrs on 10w30. Current one getting the same treatment. I don't feel the need to overthink the issue.