Generator oil question.

[Richbeck]

I have a generac np-66g and it says to use 10w/30sf oil in it, well 10w30sf is a little hard to find, what are you guys running for oil?

[BFlinn181]

The letter designations can be confusing, but actually you're searching for oil certified in the late '70s to the late '80s. S designates gasoline engine oil. SA was the first label by ASI for oil made in the 1920s. As oil improved, the letter went up the alphabet. A bit better oil was developed and was SB in WWII up to 1951.

Currently, the best oil is SN. Any oil with the second letter further up the alphabet than SF is improved over SF and will be better for your generator.

[Richbeck]

ok that makes sense, but they make a 4 stroke motorcycle oil with the sf on it. but i just found it in 20w50sf, not 10w30sf, Generrac have a 10w30sn part Number 0j5139, maybe ill buy it.

[BFlinn181]

An SM or SN ASI marking will have better additives and other features than a SF or SG. Why not buy the 'new and improved' oil with a higher notation. No generator manufacturer is going to be upset or void a warranty on a better oil than they recommend.

http://www.pqiamerica.com/apiserviceclass.htm

http://www.cartalk.com/content/sg-sf...n-it-comes-oil

[Gary RVRoamer]

It's the 10W30 that is the important part - that is the viscosity. The SF is an API "service class", and as others explained the SF designation has been superseded as oils have been improved. The current good stuff is SN and it is backwards compatible with the previous ones. You can use it in place of SF, SH, SJ, etc.

You can learn more about the API service class designation at API | Oil Categories

[Richbeck]

ok, sn it is thank you guys.

[rogbeis]

Here in northern Minnesota I use a synthetic oil 5w30 in the diesel gen so it will start when cold and plug in the chassis block heater while I have breakfasts. Works well with no oil consumption by the generator.

[mojoracing]

5-30 mobil 1 in my generators. Ive had both generac and onan and frankly I dont think my onan will live as long as my generac did (7000 hrs) For the last half of its life, I ran whatever I had left over or was cheapest. After all those hours and 4 starters, it finally gave up the ghost.

[Richbeck]

This generac is a 1994 model with 600hrs on the meter in the center of the dash, i think that is how you see hrs.

[BFlinn181]

Originally Posted by Richbeck

This generac is a 1994 model with 600hrs on the meter in the center of the dash, i think that is how you see hrs.

The SF code was obsolete by 1994. You are correct on the hour meter, unless it was replaced or disconnected, your generator has run 600 hours.

[Mr_D]

Originally Posted by mojoracing

5-30 mobil 1 in my generators. Ive had both generac and onan and frankly I dont think my onan will live as long as my generac did (7000 hrs) For the last half of its life, I ran whatever I had left over or was cheapest. After all those hours and 4 starters, it finally gave up the ghost.

Onans have been known to go 25,000 hours with just normal maintenance.

[mojoracing]

I think your talking diesel at those kind of hours. Anyhow, my point is that most folks will never crack 2000 hours on their gens. I would run that generac until it shut down from low oil, dump some more of whatever I had laying around and fire it back up. For at least half its life, the only way it had an oil change was to run it low on oil and add more. I know most will never consider such a maintenance plan and I dont either (the coach was on its last leg) but I think we can put way too much emphasis on some things. These things are pretty tough, change your oil regularly with whatever is called for and you most likely will never have a problem. Dont overthink it.

[Richbeck]

I wish mine was diesel, they sim to class oil different for small 4 cycle engines then automotive, like my dirt bike was 10w40SF, i have found this oil but not 10w30sf, so i used 30w-sn. and winter time i will do 10w30sn.