Generac Generator Oil Requirements

Status
Not open for further replies.
Joined
Jul 14, 2012
Messages
195
Location
Bucks County, PA
Generac says use straight 30 for summer ( temps above 32 F). I'd prefer to use a FULL SYNTHETIC. But, it's hard to get full synthetic is straight 30. Am I going to hurt the engine by using 10w30 in a full synthetic like Mobil 1? Or stick with conventional oil in straight 30W? Thanks.
 
Royal Purple make a straight 30 syn #831-01030 and Jegs will put it on your front door step for free.
 
Originally Posted By: Hot_Ajax
Generac says use straight 30 for summer ( temps above 32 F). I'd prefer to use a FULL SYNTHETIC. But, it's hard to get full synthetic is straight 30. Am I going to hurt the engine by using 10w30 in a full synthetic like Mobil 1? Or stick with conventional oil in straight 30W? Thanks.

10w30 is fine...synthetics won't have much if any VI.

I just picked up a 5 qt jug of Castrol at Walmart for $17. There always seems to be close outs on 10w30 synthetics.
 
Any quality synthetic will by its very nature, carry the cold flow properties of a 10w30. They rarely use the signification of SAE30 by itself. Royal Purple and Amsoil place the designation of SAE30, but Amsoil also specifies it carries the 10w30 cold flow benefits.

We use the Amsoil Small Engine 10w30 oil most often for customers that want synthetic in their aircooled small engine. However, a quality diesel rated synthetic also tends to hold up to the torture that is a small engine running for long periods of time.
 
I typically use Amsoil HDD 5W30 in pretty much all of my OPE / small engines, including my Generac genset. The generator is one of the few pieces of equipment that I own that does need to operate in both extreme cold in the winter and summer heat. With synthetic oil, it does just that with little drama, and no oil burning that I can see.

I just recently ran it for 110 hours straight with no stops this past December during an ice storm and it performed flawlessly. It was below 0 F outside the entire time.
 
GC 0w30
smile.gif
 
Originally Posted By: LotI
Originally Posted By: Hot_Ajax
Generac says use straight 30 for summer ( temps above 32 F). I'd prefer to use a FULL SYNTHETIC. But, it's hard to get full synthetic is straight 30. Am I going to hurt the engine by using 10w30 in a full synthetic like Mobil 1? Or stick with conventional oil in straight 30W? Thanks.

10w30 is fine...synthetics won't have much if any VI.

I just picked up a 5 qt jug of Castrol at Walmart for $17. There always seems to be close outs on 10w30 synthetics.


Thanks for responding. Question: What does "VI" mean, where you wrote that "synthetics won't have much if any VI". Not sure what VI means. Thanks.
 
Originally Posted By: Hot_Ajax

Thanks for responding. Question: What does "VI" mean, where you wrote that "synthetics won't have much if any VI". Not sure what VI means. Thanks.



VII's are known as polymeric viscosity index improvers. They are added to an oil formulation to allow a finished oil to have a higher apparent viscosity at operating temperatures, but still retain good cold flow characteristics by starting off with a thinner base oil.

To explain this another way, in a conventional SAE 30 oil, the oil only has one main requirement: it has to be between a certain viscosity range at 100C (212F) (9.3 to 12.5 cSt for a 30 grade oil). Thus, a formulator would choose a base oil that would fall within that range when heated to 100C.

However, when looking at multi-grade oils (such as 5W30 for example), these oils have to meet additional requirements. The 30 means that it still has to be between 9.3 to 12.5 cSt at 100C, but the 5W implies that the oil must not exceed 6200 cP at -30C (-22F). So any oil with a W in the grading will have an additional cold specification to meet as well as a hot specification. In order to formulate a 5W30 in a conventional oil, a blender must start with a thinner base oil, and use viscosity improvers (VII's) that allow the base oil to thin out LESS as it's heated when compared to the same base oil without any VII's. Thus, you can start with a thinner oil for good cold temperature properties, but still end up with a finished product that will fall between 9.3 and 12.5 cSt at 100C.

However, the trade off is this: VII's can and do break down under extreme use, and thus an SAE 30 grade will be more robust in those particular cases where a 10W30 or 5W30 oil may break down, leaving you with an oil that is below 9.3 cSt at 100C.

But in the world of synthetic oils, the base oils used have a naturally high viscosity index (a measure of how much an oil thins as temperature increases). Thus, a synthetic oil can use a lot less VII's (if any) when used in formulating a multi-grade oil. So where a conventional 5W30 oil may have a certain percentage of VII's, a synthetic will have next to none, if that. Also, the quality of VII's used also determine their performance and longevity under extreme conditions as well, so a premium product may use better VII's than a no-name brand (for example).

What this means in terms of your generator... If a conventional SAE 30 is recommended, it is to avoid the issues created by VII's in this particular case. An air cooled generator engine can run very hot under heavy load and in hot weather, so an SAE 30 is a safe choice for the manufacturer. But, if you decide to use a multi-grade oil, a fully synthetic 5W30 would likely stand up to the heat even better, but would also give you better flowability at room temperature and below (down to very cold temperatures).

Hopefully that helps a bit. As I said, I use synthetic 5W30 in my generator and other power equipment.
 
Originally Posted By: il_signore97
Originally Posted By: Hot_Ajax

Thanks for responding. Question: What does "VI" mean, where you wrote that "synthetics won't have much if any VI". Not sure what VI means. Thanks.



VII's are known as polymeric viscosity index improvers. They are added to an oil formulation to allow a finished oil to have a higher apparent viscosity at operating temperatures, but still retain good cold flow characteristics by starting off with a thinner base oil.

To explain this another way, in a conventional SAE 30 oil, the oil only has one main requirement: it has to be between a certain viscosity range at 100C (212F) (9.3 to 12.5 cSt for a 30 grade oil). Thus, a formulator would choose a base oil that would fall within that range when heated to 100C.

However, when looking at multi-grade oils (such as 5W30 for example), these oils have to meet additional requirements. The 30 means that it still has to be between 9.3 to 12.5 cSt at 100C, but the 5W implies that the oil must not exceed 6200 cP at -30C (-22F). So any oil with a W in the grading will have an additional cold specification to meet as well as a hot specification. In order to formulate a 5W30 in a conventional oil, a blender must start with a thinner base oil, and use viscosity improvers (VII's) that allow the base oil to thin out LESS as it's heated when compared to the same base oil without any VII's. Thus, you can start with a thinner oil for good cold temperature properties, but still end up with a finished product that will fall between 9.3 and 12.5 cSt at 100C.

However, the trade off is this: VII's can and do break down under extreme use, and thus an SAE 30 grade will be more robust in those particular cases where a 10W30 or 5W30 oil may break down, leaving you with an oil that is below 9.3 cSt at 100C.

But in the world of synthetic oils, the base oils used have a naturally high viscosity index (a measure of how much an oil thins as temperature increases). Thus, a synthetic oil can use a lot less VII's (if any) when used in formulating a multi-grade oil. So where a conventional 5W30 oil may have a certain percentage of VII's, a synthetic will have next to none, if that. Also, the quality of VII's used also determine their performance and longevity under extreme conditions as well, so a premium product may use better VII's than a no-name brand (for example).

What this means in terms of your generator... If a conventional SAE 30 is recommended, it is to avoid the issues created by VII's in this particular case. An air cooled generator engine can run very hot under heavy load and in hot weather, so an SAE 30 is a safe choice for the manufacturer. But, if you decide to use a multi-grade oil, a fully synthetic 5W30 would likely stand up to the heat even better, but would also give you better flowability at room temperature and below (down to very cold temperatures).

Hopefully that helps a bit. As I said, I use synthetic 5W30 in my generator and other power equipment.


Well stated. Thanks a lot for explaining this. I think I will go get some multi vis oil and stick it in there. Big help with this explanation. Enjoy the Stanley Cup games. J
 
Originally Posted By: Hot_Ajax


Well stated. Thanks a lot for explaining this. I think I will go get some multi vis oil and stick it in there. Big help with this explanation. Enjoy the Stanley Cup games. J



No problem. Just be sure to use a full synthetic if you're going to go with 5W30. Cheers
11.gif
 
Originally Posted By: Hot_Ajax
Originally Posted By: webfors
RT5 is what that generator needs!

I use it in all my small engines.


What is RT5?
It's BITOG-speak for Rotella T5, a nice Semi Synthetic 10w30 made by Shell. I use it in my Subaru-Robin generator after much research here.
 
Originally Posted By: RF Overlord
Originally Posted By: Hot_Ajax
Originally Posted By: webfors
RT5 is what that generator needs!

I use it in all my small engines.


What is RT5?
It's BITOG-speak for Rotella T5, a nice Semi Synthetic 10w30 made by Shell. I use it in my Subaru-Robin generator after much research here.


And not just any 10W30. It has a HTHS of 3.5+ which is important for a generator that sees summer duty.

I use it all winter in my snowblower. No problems starting, always first pull.
 
Originally Posted By: webfors
Originally Posted By: RF Overlord
Originally Posted By: Hot_Ajax
Originally Posted By: webfors
RT5 is what that generator needs!

I use it in all my small engines.


What is RT5?
It's BITOG-speak for Rotella T5, a nice Semi Synthetic 10w30 made by Shell. I use it in my Subaru-Robin generator after much research here.


And not just any 10W30. It has a HTHS of 3.5+ which is important for a generator that sees summer duty.

I use it all winter in my snowblower. No problems starting, always first pull.


Webfors, what is the meaning of HTHS of 3.5? Thank you.
 
Originally Posted By: Hot_Ajax


Webfors, what is the meaning of HTHS of 3.5? Thank you.


How thick the oil film is in high temp, high shear (hence HTHS) applications:

http://www.astm.org/Standards/D4683.htm

Search bitog for 'hths'. There have been many discussions about this over the years.
 
Status
Not open for further replies.
Back
Top Bottom