Need help picking correct oil for my 25 year old 19hp twin Generac generator

[sixdogs]

What is the correct oil to use in my 25 year old 19hp, twin cyl, air cooled Generac generator. This is from the old days with higher ZDDP in the oil and I don't want to screw up my house generator with modern oil. The generator has test run more than actual use and only has maybe 15 hours of non-test use. So the rings aren't even seated yet.

Here's my engine, front ID tab and owner's manual oil requirement

What I have been using is some ag gas engine oil that correct for the but is 30W and I want to go lighter like 10W30 or even synthetic for the winter. I could also use modern oil and just add a little ZDDP additive. I have done this with other gas engines and know the % mixture from company instructions

But, here's what I saw the other day in a shop but I know nothing of these oils. Does anyone know anything about these?


My plan at the moment is confusing. Should I just use modern synthetic gas engine oil if OK for rings seating, add a little ZDDP and call it good or go with a pre packaged oil as shown in the pictures? Are they really different? Any knowledge or help appreciated.

 

[RustyA]

If the zinc content is a concern for you I would consider a diesel rated oil like rotella t6 full syn 5w40. Zinc content is greater than newer G rated gas oils that are formulated for longer catalytic converter life. I use it in all my non emission engines, ATV, zero turn, splitter, and boats.

 

[grsthegreat]

I maintain generac standbys for a living……i only use mobil 1 5W30 here ….. its what generac recommends. Even for generators back to 2004 ish. Those are the oldest ones i maintain. I dont use any additives, and generac does not recommend ever using an additive.

just my opinion.


but im in north idaho. For warmer climates the older 2004 era units had a chart for oils. This was back when synthetics were just gaining ground. Nowdays they just recommend a full synthetic 5W30 after breaking in engine.. heres a screenshot of older manual

 

[sixdogs]

I maintain generac standbys for a living……i only use mobil 1 5W30 here ….. its what generac recommends. Even for generators back to 2004 ish. Those are the oldest ones i maintain. I dont use any additives, and generac does not recommend ever using an additive.

just my opinion.


but im in north idaho. For warmer climates the older 2004 era units had a chart for oils. This was back when synthetics were just gaining ground. Nowdays they just recommend a full synthetic 5W30 after breaking in engine.. heres a screenshot of older manual


View attachment 857295

Thank you. I bought this generator in 1999 so it's old school. Do you know if I can use synthetic from an engine built back then? Do they sell a specific break-in oil? I have JD diesel break-in oil and I know that has higher ZDDP. How long is the break-in period?

 

[RandyT]

All of the modern small engine oils contain ZDDP So Briggs, Kohler, Honda, Stens, Kawasaki, Kinetix, other brands small engine oils will have the required additives for your air cooled engine

 

[RandyT]

Been working on, rebuilding, and replacing small engines on lawnmowers etc for over 26 years, and I have never come across an OEM that recommends the use of breakin oil in any of their engines even when new out of the box.

 

[grsthegreat]

generac does not use a break in oil in new engines. they come with dinosaur 5-30 oil from factory, and they recommend swapping to synthetic after 25 run hours. but, if you add winter heat option (wrap oil filter heater) they recommend swapping to synthetic immediately. they dont want ANY additives used.

 

[5030]

Been working on, rebuilding, and replacing small engines on lawnmowers etc for over 26 years, and I have never come across an OEM that recommends the use of breakin oil in any of their engines even when new out of the box.

Actually, Generac does and they recommend running the initial factory fill for (I believe) 20 hours. Cannot remember and mine is pretty old as well, mine is a 19KW for the house standby and ever since I've been using Rotella T5 in it plus a filter change and air cleaner renew every spring. Interestingly, my steel cabinet is about rusted out and Generac sold me an aluminum enclosure of the same square design as my old cabinet is. Wasn't cheap but cheaper than buying a new complete unit. I also have a JD diesel powered 30 KW standby to run the shop and all my 3 phase equipment.

 

[sixdogs]

Actually, Generac does and they recommend running the initial factory fill for (I believe) 20 hours. Cannot remember and mine is pretty old as well, mine is a 19KW for the house standby and ever since I've been using Rotella T5 in it plus a filter change and air cleaner renew every spring. Interestingly, my steel cabinet is about rusted out and Generac sold me an aluminum enclosure of the same square design as my old cabinet is. Wasn't cheap but cheaper than buying a new complete unit. I also have a JD diesel powered 30 KW standby to run the shop and all my 3 phase equipment.

What weight Rotella T5 are you using? I might have the same 19hp engine.

 

[90cummins]

Zddp isn’t a requirement for Generac air cooled engines or any othe fact.
Zddp was essential for cam lifter protection in cars especially those with higher performance engines with wilder high lift camshaft’s & heavy valve springs.
Oils have been reformulated to with other additives to replace the zddp.
I would use a quality 10-30 for mild climates & a 5-30 synthetic for colder climates.
Small diesels depending on design such as an air cooled L series Yanmar require a diesel oil to protect the cam/injection pump lifter from scuffing from my experience.
I’ve never seen a worn cam/ lifter on air cooled small engines.
I just rebuilt a Generac 25kw 990cc v-twin & the cam was spotless.
It came in because of excessive blow by because a foreign object went thru it. New pistons & rings with a quick hone & it’s ready for service.
Go to bobistheoilguy forum for everything you want to know about oil for any application.
Great website!!
90cummins