Onan QG 4000 RPM

[Rich Biebel]

They are my favorite model and I own 2 myself....

Most Every Class C Motorhome has one.....

I have one in my trailer and one in my Class C Motorhome....

They are not like the older 1800 rpm units for sure and are far less durable.

Older models were twin cylinder flathead engines that ran 1800
From a 4 to a 7 KW

20 years ago they started making their modern versions....

Single cylinder 3600 rpm....on the QG 4000's......The 5.5 and 7kw's are twin cylinder and nothing like the 4's....

Onan stopped making their own engines back then and everything they build uses an import built engine......No big surprise....

For those that don't know.....
A modern Onan QG 4000 has NO low oil shutdown....
If it runs low on oil it will at the very least seize up and usually much worse.....

The aluminum rod usually blows up and takes out the engine.

They only hold about 1-1/2 quarts of oil and it should be changed often.....and checked often.....No filter.....splash oil....

I saw more than one that blew up and really busted up everything in there.....changing an engine is not a good option so it winds up being trashed....

[Glenn Briglio]

Originally Posted by Rich Biebel

They are my favorite model and I own 2 myself....

Most Every Class C Motorhome has one.....

I have one in my trailer and one in my Class C Motorhome....

They are not like the older 1800 rpm units for sure and are far less durable.

Older models were twin cylinder flathead engines that ran 1800
From a 4 to a 7 KW

20 years ago they started making their modern versions....

Single cylinder 3600 rpm....on the QG 4000's......The 5.5 and 7kw's are twin cylinder and nothing like the 4's....

Onan stopped making their own engines back then and everything they build uses an import built engine......No big surprise....

For those that don't know.....
A modern Onan QG 4000 has NO low oil shutdown....
If it runs low on oil it will at the very least seize up and usually much worse.....

The aluminum rod usually blows up and takes out the engine.

They only hold about 1-1/2 quarts of oil and it should be changed often.....and checked often.....No filter.....splash oil....

I saw more than one that blew up and really busted up everything in there.....changing an engine is not a good option so it winds up being trashed....

What oil do you like for this generator?

[jmcarter]

Interested in Rich's recommendation as well. The oil fill tag attached by the Onan technician indicated a different oil than is recommended by their manual. My previous Onan was a larger model with filter and at the initial 50 hour change the oil looked better than this one did at 20 hours. Going to make sure I don't go past 30 hours without a change from now on.

[Rich Biebel]

Onamax is the oil they sell for every machine they build

It's 15-40 which is/was commonly used in Diesel's for years.

I stopped buying it from Onan and have been using 15-40 Delvac. That is what our bulk supplier sells now and we buy it in bulk as well as in qt cases...

In winter I switched most commercial users of Onan's to a 10-30 oil

All air cooled engines work their oil over very hard.

Typical 7kw gas Onan's used in commercial trucks, when the oil is changed it's in bad shape if gone to many hours.....real bad!

Oil does more than lubricate.....it also helps to cool and carry heat away from various engine parts.

The 7kw's develop cylinder head failures from the heat.
Fresh oil helps....
Poor installs kills them and the same goes for the 4kw machines but not as bad.....

Using synthetic oil is not a bad idea but it still needs to be changed often because of how bad it deteriorates from the heat.....

[voltdr]

After I switched to 15W-40, I noticed that the oil consumption went down as well.
Dan

[KRatcliff]

Speaking of oil changes I am not sure the difference between the commercial QD 8000 and the regular QD 8000. I have two of the regular QD 8000 and I recently changed the outer panel to the commercial version to make the oil changes and fuel filter changes easier (for me). I wish all of them came with that removable panel. Seems like I hit the 150 hrs pretty quickly on each of them.

What is the real differences between the commercial and the regular Quiet Diesels other than that convenient panel?

[Rich Biebel]

There is very little differences from most machines from RV to CM models.
The added side access door is for use in some trucks with limited access below the machine but direct access to that door area.
Many diesel pushers have the older 7.5 diesels. Very similar to the newer 8’s
Those diesel pushers more often than not have the generator fixed mounted in front. No side access. Bottom trap door for service only. Not fun to do.
Some of those MH’s have slide mounts for the generator.
I assume Onan just added the side door to cover various installs and access.
Diesel oil changes can go longer than 150 and 250 was what was their recommended hours for changes. Changing it more often does no harm that’s for sure. They only hold 3 qts

[Ed Carpenter]

Originally Posted by Rich Biebel

They are my favorite model and I own 2 myself....

Most Every Class C Motorhome has one.....

I have one in my trailer and one in my Class C Motorhome....

They are not like the older 1800 rpm units for sure and are far less durable.

Older models were twin cylinder flathead engines that ran 1800
From a 4 to a 7 KW

20 years ago they started making their modern versions....

Single cylinder 3600 rpm....on the QG 4000's......The 5.5 and 7kw's are twin cylinder and nothing like the 4's....

Onan stopped making their own engines back then and everything they build uses an import built engine......No big surprise....

For those that don't know.....
A modern Onan QG 4000 has NO low oil shutdown....
If it runs low on oil it will at the very least seize up and usually much worse.....

The aluminum rod usually blows up and takes out the engine.

They only hold about 1-1/2 quarts of oil and it should be changed often.....and checked often.....No filter.....splash oil....

I saw more than one that blew up and really busted up everything in there.....changing an engine is not a good option so it winds up being trashed....

Good to know. I just bought 28’ trailer extra height. Looking at getting a generator. No a/c right now but want to put 2 15 units in it. So it will have that plus lights, plugs for charger air compressor etc. would an Onan 4000 be enough? Thanks Ed

[340Cuda]

I have noticed more racers are going to the inverter style generators like the Honda EU7000iS and the Honda EU3000iS.

They are very quiet and only run as many RPM as they need to cover the load.

However they appear to need to have the generator door opened and pulled out on a slide to get proper cooling.

Connecting an exhaust pipe on the EU3000iS may take a special kit.

Of course these generators are pretty expensive but other inverter generator are starting to show up on the market.

However the Onans are not inexpensive either.

[Mike Pearson]

Originally Posted by Ed Carpenter

Good to know. I just bought 28’ trailer extra height. Looking at getting a generator. No a/c right now but want to put 2 15 units in it. So it will have that plus lights, plugs for charger air compressor etc. would an Onan 4000 be enough? Thanks Ed

4000 is barely enough for a trailer. I put a 6.5 in mine and it runs everything very easily. I bought an old Onan 6.5 with low hours for $500. It’s one of the 1800 rpm twin cylinder units. They are very quiet and reliable. Just search on Craig’s list or Facebook marketplace. There are usually some for sale there.