Yamaha EF2000is Generator Oil Consumption Mystery

[boraticus]

Our Yamaha EF2000is inverter generator jut turned 600 hours. Last week I did an oil change and as usual, the oil was down approx. 2.5 to 3 oz. Which has been the normal consumption rate for every 30 hours of use.

I was getting low on the 5W50 Castrol Edge synthetic so I decided that if the generator is using oil at that rate, I might as well just use whatever I have around that's suitable for the purpose. I had about 1.5 quarts/liters of 5W50 left in the jug. I found a quart of Tech 2000 15W40 and blended it with the 5W50. I used the blend for a full 400 ml. (13.5 oz) fill and cleaned the spark plug.

A few days later, I was refueling the generator and did my usual 30 hr. oil check. The oil level had not dropped? The machine is getting close to 40 hours since the last oil change and oil consumption still remains stable. I've also been checking the exhaust pipe for oil residue and it's also stopped. When the machine was using oil, there would always be a drop of clean oil hanging at the end of the pipe.

So, the big mystery is..... Has the machine finally broken in properly or did the oil blend contribute to less oil consumption? I guess I could go back to using straight 5W50 synthetic on the next change to see if oil consumption goes back up.

What do you folks think?

 

[oggb]

I'm guessing it's either rapidly shearing the 5w50 and that's what's causing consumption.

Why not use something more shear stable like 10w-30 or 15w-40 HDEO?

 

[boraticus]

I used a variety of quality conventional HDEOs for the first couple hundred hours or so. Then I switched to synthetic oil to see if it would change things. No changes until this recent revelation.

 

[HerrStig]

My 5KW Briggs L head made in 1998 doesn't use any T6 at all.

 

[boraticus]

I've owned dozens of four stroke small engines that never consumed oil like this generator did.

I have a 6kw Kubota diesel powered generator that's 32 years old with over 6000 hours on it. It has never and still doesn't burn a drop between 150 hour oil changes. I usually run Rotella 10W30 or 15W40 depending on temperatures.

This sudden improvement in oil consumption is nice to see but still undetermined.

 

[linksep]

What JRed said.

Yamahas are super premium generators known for reliability and long life. Yamaha specs 10w40 or 10w30 as their recommended oil and I'm sure that recommendation is based on keeping their excellent reputation intact. Try one of those and report back. You're in Canada so the genny is going to run cooler than if you were in Death Valley California and a 10w30 will provide perfectly acceptable oil film & lubrication. Yamaha specs a straight 20 weight for operation from 0-27 degrees C if not using a multi-weight oil.

From your most recent post you say you run a 10w30 or 15w40 in a much larger much more highly stressed diesel engine (probably the manufacturer recommended oil weights) yet you run an Xw50 (way above the recommended oil weight) in a tiny low stress gasser? I don't understand the logic there.

(By stressed I mean cylinder pressure and bearing pressure.)

 

[boraticus]

The logic is that the generator was eating 10W30 and 15W40 as well as 5W50 synthetic. Didn't matter what oil I put in. It consumed it at a considerable rate of 3 to 4 oz. ever 25 to 30 hours. I went with the wider range of 5W50 to see if it would make a difference and it didn't.

 

[linksep]

OK, the fact that you have had significant consumption with other weights wasn't clear to me when I read your original post.

I would still try other oils in the 10w to 15w 30 to 40 spectrum (10w30 to 15w40), maybe a HDEO, or maybe even straight weight depending on your expected operation temperature range before your next OCI.

 

[boraticus]

Update:

After running the oil blend for an extended period of time (60 hrs), I decided to check the oil and noticed that it was down a bit. It took 2 oz. (60 ml) to bring it to max level. That's a marked improvement. It would normally consume that in 25 to 30 hrs. I still see accumulation of clean oil on the end of the exhaust pipe extension, but nowhere nearly as much. Will have to see if this is the best it will get or if it improves with time. It would seem a bit strange to take up to 600 hours to properly seat the rings, if that's what's causing the oil consumption?

Another thing I'm beginning to ponder is if the crank case ventilation tube/valve might be partially blocked? If there's too much pressure in the crank case, I can see that possibly causing oil to be blown past the rings.

Anyone have thoughts on that idea?

 

[TFB1]

Originally Posted By: boraticus
I've also been checking the exhaust pipe for oil residue and it's also stopped. When the machine was using oil, there would always be a drop of clean oil hanging at the end of the pipe.


What do you folks think?


I think if it had oil hanging on the exhaust pipe, it'd be using at least double the amount of oil that you stated with every tank full... Two or three oz in 30 hours does not a droplet make...

 

[boraticus]

Not sure I understand your point?

When the machine was using twice as much oil in the same period of time, there was always a droplet of oil on the tip of the exhaust pipe. Now it takes much longer to accumulate. The oil consumption has improved to levels that are acceptable compared to the previous 599 hours of use.


Originally Posted By: TFB1
Originally Posted By: boraticus
I've also been checking the exhaust pipe for oil residue and it's also stopped. When the machine was using oil, there would always be a drop of clean oil hanging at the end of the pipe.


What do you folks think?


I think if it had oil hanging on the exhaust pipe, it'd be using at least double the amount of oil that you stated with every tank full... Two or three oz in 30 hours does not a droplet make...

 

[bmwpowere36m3]

For oil droplets to accumulate on the exhaust tip I'd assume the oil consumption would be high. If the engine is run up to temp for reasonable amounts of time... the exhaust should be blowing and/or evaporating most oil in the exhaust. Maybe its a leak, leaking down on the exhaust.

*edit* missed your point about it being "clean" oil... if its truly clean, then its likely not going thru the combustion process. Leads more credibility to a leak vs. oil consumption (burning in engine via worn rings, clogged breather and/or worn valve guides/seals).

 

[boraticus]

The oil comes with the exhaust gasses from the inside of the pipe. I also keep very good records concerning fuel and oil consumption. There are no leaks anywhere. I'm beginning lean toward the possibility of high crankcase pressure and/or a possibly blocked CCV. I'll have to check that aspect out.


Originally Posted By: bmwpowere36m3
For oil droplets to accumulate on the exhaust tip I'd assume the oil consumption would be high. If the engine is run up to temp for reasonable amounts of time... the exhaust should be blowing and/or evaporating most oil in the exhaust. Maybe its a leak, leaking down on the exhaust.

 

[Cujet]

I'm still going with rings or valve guides as the source of your very minor consumption. While most engines will get hot enough to roast engine oil in the exhaust, it's entirely possible that in this case, the exhaust is cool enough under certain conditions to simply transport the oil to the tip of the muffler, unmolested.

The consumption is so low, it's only a problem because the sump is small and the oil shutoff does it's thing.

While it may be you posting elsewhere, I've read that other users have Yamaha generators that consume a touch of oil too.

As you may know, I'm not a fan of ultra thin oils. Especially thin oils that contain a huge quantity of viscosity index improvers. Your 5W-50 may be such an oil.

I may have mentioned this before, but all engines consume oil, and I know you fully understand this. Some engines "appear" not to consume oil because combustion by products offset some of the oil volume. If it were not so, the oil would remain perfectly clean.

There are huge discussions in the piston aircraft engine world, about engines that consume no oil. (I've got a good one) is what people think.

Yet, upon oil change, the pitch black oil is chock-a-block full of contaminates. Let it sit in a bucket for a few months and the bottom 10% of the bucket is solid sludge.

I'm a fan of oil changes every 25 flying hours, regardless of consumption.

My Cessna Cardinal uses about 1 quart every 4 hours. That's normal, safe and completely acceptable. For my engine, the maximum allowed consumption rate is 0.75 quarts per hour, or about 3 quarts in 4 hours.

 

[JR]

Put some MMO and good stout oil in the crank. Start it, idle til up to temp then run under max load the machine will hold. And walk away. Will set rings good.

Bought a predator 5.5kw, used 72hrs. Light to no load. Was using oil
I put a little over 6kw load for 25hrs. Dumped the mmo and m1 15w50. Must of had a graze on the bore, and my load seated the rings.
My best rental. Service every 100-125hrs no a drop low.


-harvey

 

[boraticus]

This mystery just keeps getting deeper. As previously mentioned, after the 600 hr. oil change, I monitored oil consumption and accumulation at the end of the exhaust pipe. I was encouraged to see a reduction in oil consumption and a clean/dry exhaust pipe for almost 60 hrs of use. This weekend, I took another reading at approx. 687 hours and noticed the oil was down 2 0z. (60 ml) and an oil droplet accumulating on the tip of the exhaust again??? It seems to be going back to it's usual oil consumption rates.

I tested the CCV system from the engine valve cover to the carburetor intake port. All was clear and working as intended.

It's soon due for it's 100 hr. oil change. I have some 10W30 and 15W40 Rotella on hand. Maybe I'll give it another shot of one of those? Something is truly bizarre here.

 

[JR]

15w-40 may help. It is a stout shear resistant diesel oil. Can't go wrong.


Harvmey

 

[Clevy]

Air cooled engines tend to be built a bit loose to accommodate thermal expansion. So during warm up some oil gets by the rings til the piston expands in the cylinder.
Couple that with the 5w cold rating and you'll see some consumption.
Using an oil with a 10w or 15w cold rating will lessen consumption during warm up because it starts off a bit thicker and lessens oil passing by the rings.
I own/run a large construction company. I've got 6 generators and 16 gas powered air compressors. Over the decades I've tried every single oil grade out there and have found that in summer a 15w-40 is perfect during summer and a 5w-30 is ideal in the winter. 100 hour interval,and no measurable consumption however there is always a bit of fuel dilution,Expecially if they only run an hour or 2. Running all day the oil smells slightly like fuel but isn't flammable.
If I only run the engines an hour or 2 even new oil is fuel diluted enough to light up,for a moment

 

[boraticus]

Thanks for the comments folks.

I'm going to try some 15W40 Rotella next fill. However, changing to oil viscosity doesn't explain why oil consumption had dropped off for 60 or so hours then back up for the last 27 hrs?

Not that this is a world ending issue. I just like to have an understanding of why the generator is so quirky when it comes to oil consumption???

 

[andyd]

2 oz? That is like 4 tablespoons. That is easily managed. A tad low tells me the oil isn't gassed very much. Keep an eye on the oil level as you should with all OPE.