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Synthetic Oil In Generac Generator - Good Idea?


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#1 Kevin H

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Posted 05 May 2012 - 09:21 AM

I have an old Generac generator in my '99 Dolphin. It has not been run much at all in the past 5 years - Perhaps 10 hours at most. I am going to change the oil, filter and air cleaner. Is there any benefit to putting synthetic oil in it? If so, are there any recommended brands? Do I need a special filter for the synthetic, or will a standard one work?

Any other things I should do to get this up to speed?

As always, thanks a lot in advance!

Happy Trails!! -- Kevin

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#2 geysergazers

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Posted 05 May 2012 - 10:31 AM

I use synthetic oil in the lawnmower. Synthetic oil stands higher temperatures and air cooled small engines are notorious for running hot. One caution RE old engines though: when I switched to Mobil 1 in our old Dolphin MH the front crankshaft seal began to leak.

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#3 RV

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Posted 05 May 2012 - 04:31 PM

I run symthetic in a 15 KW Generac whole house genset, it came from the factory with synthetic. It is air cooled, but I can't speak to the older ones. They do flow better cold for cranking and as long as you have the hours on the generator to be past the first oil change synthetic should benefit you. It shouldn't hurt anything.

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#4 gillig_cat

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Posted 05 May 2012 - 04:32 PM

What weight dino oil does Onan suggest for the 6.3 lpg, and approx capacity....no manual.
Also, will most syn's weights work?

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#5 qwcslvr1

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Posted 05 May 2012 - 05:14 PM

Kevin, I recently spoke to a Generac factory rep on this very topic. He stated not to use synthetic on the older gensets. Fine after breakin on newer units. I have a NP66g, similar vintage, 6600 watts.

Pat

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#6 Kevin H

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Posted 05 May 2012 - 08:33 PM

I recently spoke to a Generac factory rep on this very topic. He stated not to use synthetic on the older gensets.

Thanks everyone for your input.

Pat - did the Generac rep say why he recommended NOT using synthetic on the older units?

-- Kevin

The richest are not those who have the most, but those who need the least.


#7 Atchafalaya_man

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Posted 05 May 2012 - 09:20 PM

Thanks everyone for your input.

Pat - did the Generac rep say why he recommended NOT using synthetic on the older units?

-- Kevin


While this is not information from Generac, the following has been discussed on many auto forums, etc.

Older engines that have run conventional oil tend to be 'dirty' inside. It's the 'sludge' one may have seen when an old engine is opened up.

The sludge contaminates can gather around the inner lip of seals on shafts, bearings, etc. and just become a part of the sealing process. Also, the older seals tend to become hard and brittle. Conventional oils tend to be thicker than synthetic, so this sealing condition works adequately.

As said, synthetic oil tends to be thinner than conventional oil. Plus, it does such a good job of 'suspending' contaminates, (and somewhat dissolving sludge), that it removes some of the sludge material that has been a part of the old seals. With that gone, and with the older seals being harder from age, they tend to let the thinner oil past, thus, a leaking seal.

When an engine is relatively new, it lacks the sludge, and the seals are pliable. Therefore, the thinner oil is held back by the seal. Also, because of the better job the synthetic does at holding contaminates in suspension, the inside of the engine stays cleaner, and does not develop sludge.

So that's some of the thinking of why an older engine should not be switched to synthetic, after it has done most of its life on conventional oil.

#8 Lou Schneider

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Posted 05 May 2012 - 11:38 PM

I'd change the oil and filter twice - if the unit has been sitting for 5 years there's likely a lot of moisture and sludge inside the engine.

Change the oil and filter, fire it up and put a good load on it for 5-6 hours or so. Something that gives the generator a good work out, like the air conditioner set on maximum cooling or a couple of room heaters (depending on weather, of course). I've even turned on the air conditioner and let it work against a room heater set on the floor underneath it if the outside temperature is moderate. This will not only get the contaminants out of the engine, but more importantly will heat up the windings in the generator and drive out any accumulated moisture.

Then change the oil and filter again, to get rid of the stuff the fresh oil has flushed out of the engine. A couple of quarts of oil and a filter aren't that expensive.

Edited by Lou Schneider, 05 May 2012 - 11:45 PM.

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