Premature thickening of engine oil

Premature thickening of engine oil seems to occur in natural gas fueled engines also. " Nitration is a chemical reaction within the oil, which causes the carbon chains to react with nitrogen dioxide (NO 2) formed during natural gas combustion, causing serious and premature thickening of the oil. This results in the formation of severe varnish and carbon deposits." Scroll down to see topic heading Nitration and Oxidation.


They make special oils for NG engines that I have seen but I never really investigated what the differences are.
Number problem I notice with NG fuel generating sets is the owners try and skimp out and don’t run them long enough and loaded enough to drive off water in the oil.
If you have impurities in your gas( like sulphur and are using something dirty like well head gas ) their is a high probability of acid formation.
High sulphur fuel oil in diesel engines and bad old days high sulpur gasoline also had this problem to a lesser extent.( think back to the 80s if your Canadian to the rotten egg smell your car produced, that was the suphur in the poorly refined fuel we used to burn )

The number one solution to this has and remains in my opinion to change your oil as required.
On most machines in stand-by use seasonally. ( its goo practice to switch from summer to winter oils in places where the temperature swing warrant it, in other situations it might simply be better to do it every 50 hours or yearly at the very least… )

Woodgas already has a lot of water in it and that might make things even more important to watch in clold weather that you don’t run an engine cold and wet before storage.

Strictly my opinion:
If you see woodgas engine oil thickening the first thing I worry about is tar vapour going throughh the systems often enough to get into the oil.
This is easy to spot when you check your intake and might lead to sticky rings and high oil consumption first.
I can see the products of dirty gas and pick them out right away just by the colour more brown than black, thick and sometimes it even smells off

High detergent oils rated for diesels are probably better at dealing with woodgas than gas engine oils.
I am thinking about the additives that clean and hold fine carbon dust in suspension better than other oils.

Just opinion however.


Wallace, Marcus and I have found the really nice Diesel rated oils thicken very quickly. I was using Mobil1 Synthetic 15w40 1300 Super and with my charcoal gasifier I noticed it got black sooner and if I didn’t change inside of 1500 miles it could go sideways. That’s with about a 50/50 mileage of gasoline or charcoal gas. I never had the truck long enough to tell if the High Mileage oil that I swapped for was doing any better, it was Semi Synthetic gas engine rated.

I don’t know what oil Marcus was using, probably Shell Rotella synthetic diesel oil since it helps those older engines.

I wonder if it’s the NOx from combustion, or Carbon Monoxide doing most of the sludging. I ran water drip but only about a drop per second or so. I didn’t want to drip too much at my idle so I let the mass of my nozzle handle the brunt of the heat.

For the Sierra I am going to change my engine oil to the High Mileage Semi Synthetic stuff, 5w30 as recommended, instead of the pure synthetic Mobil1 gas oil they used at work.

I might research what Marvel Mystery Oil would do if I added it every fresh oil change, since it removes varnishing in engines and is safe to use the entire 3000-5000 mile interval.


Yes I was running rotella t6 synthetic I switched to standard 5w30 since then and have not had any sludging in the last 3000 miles, bout due for a oil change here soon. I was more surprised that finding standard oil that was not a synthetic blend wasn’t easy to do, had to call a few stores before I found it. Ended up buying a five gallon box from Napa was the cheapest I could find it


Most of what they call a synthetic these days is actual made from a base stock that comes from are you sitting down…
Syn gas and then run through a cat converter to make liquids again but unlike the FT process we know for making gasoline and diesel this one is tuned to make heavier oils with the specific intention of making higher quality base oil.

The end result is a better base oil with less wax in and tighter tolerances.
So in reality any blend of conventional cat cracker oils and Cat reformer synthetics is basically the kids of oil we were always used to, just more highly controlled and refined.

I don’t see any harm in using the synthetic stock blends, I just don;t see a lot of advantages in something we have to change often anyways ( unless you have a fancy filtration system… That would make a difference )

It might be worth getting a sample of that oil tested and find out what is in it and why its getting thicker?
Charcoal gas carries a lot of micro fine dust that’s hard to deal with and lots of what in my opinion is reversion caused carbon black.
So ya it will get black fast, thats my experience too.
I just change it a lot on my test engines and go with the theory of once it dirty enough to fail the blot test or water tests then its time chang.( anywhere from 20 to 50 hours )


I’ve already gotten rid of that oil. I always forget you can get lab analysis done nowadays for not that much.

My main concern is varnish buildup since that’s harder to eliminate, and since MMO can remove varnishes I think I’ll be fine with synthetic blended High Mileage formula and a 20% mixture of MMO. Marvel is a 5 Weight oil so it does make it a little thinner, I think someone said if you do a proper 20% mix with 5w30 it turns it to a 5w28 or something insignificant. I’m not worried about it. The creep lubrication of MMO will just keep my bearings safe.


Today’s additive packages were designed to prevent oils from reacting and changing to get thicker.
That said in the old days as the thinner light ends burned off in use conventional oils would naturally thicken a little without degrading.

The question is, and this is not the first time its asked is what is happening in lubrication oils used in woodgas applications that the additive formals are not dealing with as well as they do in conventional engines.

I understand the soot, and moister and the tars are different than what the oils were formulated for but I don;t have any answers for how they react differently.
I wonder if some posts at Bob the Oil guy would shed some light on this.

Im not a big fan of adding things to oil like MMO because I don;t understand what is in them or how they are formulated to work.

Exception being something like Restore that pastes over damaged cylinders with a temporary coating of copper and lead or things like STP that are viscosity improvers that stick to places where seals up worn out rings parts

Well that’s one of the reasons I like the diesel oils, they have a better formula for dealing with dirt and holding it in suspension between changes.
If you are getting your rings gummed up then I think you need more frequent oil changes.


Nothing gummed up yet, in the Mazda I already had a smoking issue before putting a gasifier on it. I think mostly from using too heavy of an oil even though I followed the weight chart.

With the Sierra I’ll be able to monitor things more closely, with the wonders of OBD2.


That’s strange how thick was the oil and what kind of condition is the engine in?
Compression levels?

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I don’t have diagnostic tools, I just know it was more viscous than 15w40 and was pitch black at 800 miles, it didn’t do that before charcoal gas. The oil didn’t feel gritty or have any extra texture but I wasn’t about to gamble on it.

The couple of times I’ve had to hand index off the crank shaft the compression felt about right overall.

The Mazda has over 200,000 Miles on the odometer, I bought it at 190,000. The previous owner always used 10w40 oil no matter the season if I’m to trust his logs in the manual. Smoked a lot on startup so I’m sure the oil rings were carboned down from infrequent changes. Since I changed to 5w30 it’s stopped smoking as much.


Poor maintenance

10 40 is not a very good choice on my opinion

Sounds like you a go do a compression check
Testers are cheap….

Take the oil pan off see if its full of sludge and clean it out
If it is sludges up and that material starts to move around you could clog up an oil passage and blow
The engine

Harbour freight 29 usd
Seems reasonable

I didn’t read that right Cody
I expect it to turn black fast on charcoal it’s just because of the soot
Thickening on that short of an order is strange and I would be looking at your filtration system hard to make sure you did not get a load of dirt blow into the engine somehow


All of you talking about 15-40 diesel oil sludging. That’s interesting because both times I’ve had it sludge on me was with that same Mobil 1 non synthetic diesel oil. I’ve always used Mobil 1 whenever I could afford it. Now I’m running 10-30 napa oil without any problem. I have never had a problem with the other oil outside of woodgas.


There is generally a much stronger cleaning detergent package in 15 w40 diesel oils
Most are turbo rated for high pressure and temperature ratings

They are better

They fact it’s turning so black fast and turning thick leads me to wonder if you are seeing the cleaning action remove sludge and varnish from a dirty engine

I’d pull gf a valve cover or drop the pan and try and find out if it’s the engine before blaming the oil

The mobile 1 might also have superior cleaning properties

In the old times mechanics used to advise you to stick with brand and never use a detergent or diesel oil on an old engine that ran a light duty oil because they would clean them up so much inside you would get oil leaks and sometimes oil burning as the detergents cleaned and loosened everything up inside

Before PCV valves every engine was full of sludge that ran light and medium duty oils with a non detergent mix

By the 60s they developed better oils at the same time as manufacturers needed better oils

It’s been a progression ever since of better oils that in most cases are backwards comparable with old engines but now and then you get one that’s just filthy inside and a top shelf oil will start to resolve all those years of crud

This old thing is full of sludge from the era of not so great oil and short run times poor service
I have cleaned it out by hand but it’s still dirty inside and will turn oil black fast

It also smoke murdered by way of a lot of years without service


Personally speaking I used the Mobil1 15w40 oil for almost a year before I put the gasifier on it. The oil never got like this. No other additives put in just the Mobil1.

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And I’ll echo that the small generator engines I’ve been seeing woodgas oil thickening in were newish, low hours and clean inside.

I’d thought too it was just from carbons soots thickenings.
RindertsW’s original article is saying maybe not. But reactivity to the fuels blow-by chemical components.

We will never get a special oil made up for woodgas or chargas.
So my recommendation to just use standard oil changed out much more frequently was a costs measure. I can still get SJ rated, branded oil (Valvoline?) by the five-quart jug for $14-16.00 USD. at a member’s store BiMart. The cheapest fully synthetic for me is Walmart’s at $18-22.00 USD for a five-quart jug. SP = GF6A.

Thickening will be a reality. Just start out with 5W- something reasonable for that engine. Change when you set for that engine a percieved problem. Cranking effort. Cold or hot engine running noise. Under valve cover deposits browning. Use the oil as a contaminates absorber and out with the fully loaded carrying; and in with the new clean able to absorb load up.


You are right as others have about changing the oil Steve. I look at it this way. I am saving on buying fuel. The most expensive part of owning a engine and running it. Changing the oil out more often is cheap compared to the gasoling or diesel you burn. Now that you are running on wood gas you are still saving lots of monies, change the oil and filter and keep the engine running clean. I change my oil every 2000 miles. Why it is cheap insurance compared to mantenance repairs on my engine because of oil failing to lubricate the parts in my engine.


“Nitration is a chemical reaction within the oil, which causes the carbon chains to react with nitrogen dioxide (NO2) formed during natural gas combustion, causing serious and premature thickening of the oil. This results in the formation of severe varnish and carbon deposits. Once begun, the condition worsens exponentially.
There are two major factors that must be carefully controlled if excessive nitration is to be prevented. The first is the oil’s operating temperature. Nitration becomes significant at oil reservoir temperatures of about 135°F (57°C) and becomes even more dramatic at lower temperatures.”

It seems that natural gas engines can be run at lean air/fuel ratios and in conditons where an engine will not keep itself warm. I would not have thought this was a problem, but apparently it is. Perhaps we could insulate our engine blocks, install grill shutters, and do other things to ensure that our engines are warm enough to prevent a ‘butter churn effect’ from occurring in our crankcases.

That would seem safe to say, but remember this little forum is not the whole world. There are a bunch of industrial and heavy equipment type companies out there providing ‘turn key’ systems to users such as Coors Brewing in Golden, Colorado. They are naturally going to try to make their products reliable and fool proof. So they are going to look for and demand the use of appropriate lubricants. I feel I am stating the obvious when I say this, but I think we here would do very well to keep an eye on what the big guys are doing.


Castor bean oil thickens
It’s polymorzation and actually contributes to improved lubrication
That’s the exception to the rule I think

Linseed oil thickens
We call the end product of that thickening tiles

A product of wood gas thickens oil I’ve seen it clog up rings until they are stuck and the oil consumption goes up

Why different oils behave the way I they do probably has as much to do with the fuel as whee the impurities goes
Are they being held in the oil
Are they being caught in filters
Are they sticking inside the engine

If the oil has it in suspension and your filters are catching the particulate then I think that’s the best situation

Why is Cody getting so much thicken?
I don’t on my small engines but I and running very short intervals before oil changes so I don’t wait trouble

Normally dirty oil separates over time but I know we can speed this up with a solvent
Maybe mix some 3 to 1 with white naphtha to speed up the settling and some blot tests can help identify how much is tar getting into the oil as compared to solids and how much is actual oil that has polymerized because of the contaminations

I’m not sure about the nitration part
These is so much co2 and n2 in the mix it reduces temperatures contributing leas nitric oxides
We would see high NOX o emissions test and since Wayne has done emission testing and made no mention of NOX then I am more inclined to look at it as a contamination problem with Tars and micro fine solids

Sent from my cell phone
Forgive the spelling auto correct
How do these young people type with thumbs


Thinking back to the 90s I was working in a small cracking of plant using waste oils

We cracked at low pressure to make heavy waste lubricants in number 6 heating oil for industrial burners

One of the by products were tar that would form from contamination
Acids water cracked petrol products would recombine to make tars ( and a bugger to filter and separate)

The other was oil coke full of metals sulphur and residual oils

It was mot NOX that was causing the tars but other things like acid and water reacting with the oils

There are places in an engine that could get hot enough to cause those kinds of reactions but charcoal should not cause this because all those acids and contaminants should have been cooked out

Left in the storage tanks for long periods the tar would drop out and form clumps that clogged filters

Might we find tars settling out of engine oil if we tried to settle it out in a long term test?

I think Bob the oil guy is the place to go and ask some questions of lubrication experts
We will need some oil analysis done and filters cut open
More experimentation with controls


@JocundJake said I spent the next 5 hours trying to drain jelly out of an engine.
Right, I don’t have an organic chemistry lab at my disposal where I could find out what exactly was going on in Jacobs engine. But that sure sounds like what the article was talking about.

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