flushing engine with Kerosene

[MBDiagMan]

In the old days (yes, I'm plenty old enough to remember them) I flushed a "few" crankcases with kerosene. The engines, AND the oils were WAAAaaaayyyy.... different then. Too many people insisted on running oils like Amalie and Havoline that turned to tar. This was aggravated by road draft tubes in place of PCV valves along with 160 degree Summer thermostats.

I've pulled off valve covers and seen a big hunk of black tar that was molded in the form of the valve cover. Those oils were TERRIBLE!

I flushed a few with kerosene by getting it hot as it would get then draining the oil, then pouring in a quart of oil and the rest kerosene. I would crank it and run it to about a count of three, then pull the plug again. All this was done while everything was at operating temperature.

All that said, with todays oils I wouldn't do that on a bet. If an engine is sludged in todays terms, it would be CLEAN by mid sixties terminology. If you think it's "sludged" simply change the oil and filter by pulling the plug when the engine is at operating temperature and let id drain OVERNIGHT. Those last drops that come out will be the real sludge. Keep repeating the hot oil drains about every 500 miles until the innards are clean.

Depending on the engine, use one of the diesel oils like Rotella, Delo or Delvac for this flushing process. They have lots of detergents for soot dispersal in diesel engines and will eventually make the oil in a gas engine SQUEAKY clean.

My $.02,
Doc

 

[Gary Allan]

The sludge'd engines of yesteryear were typically a pudding formed by stuff sinking out of suspension and forming up. Short trip cold gels. It was merely a time based deal. It could also be from not changing them out often enough and merely adding more oil for a protracted period. The oils would thin out, start volatilizing and thickening. Add oil as needed.

Those formations rarely destroyed the engine. Dirty, disgusting looking, sure ..but the pushrods and rockers cut their pathway ..the draining oil channeled it's way to the pickup. That's not to say that it didn't reduce the engines performance or condition.

This type of deposit formation can be removed with various methods that were developed "back in the day" and with various levels of success.

You get to the newer engines, with the vastly superior oils of today, in engines that are cleaner, and you may have a different animal. One where a hammer and chisel (wire wheel/brush) would be required and not a spoon to remove the Jello®.

That type of formation isn't going to just dissolve in any 5-10 minute kero flush.

 

[swalve]

I'm just beanplating here, but in my experience with cleaning stuff, often times different methods are required to get something back down to bare metal.

And I'm not disagreeing about any of the "why bother" advice. Everything said is true about modern oils and modern engines.

However, I can envision a scenario where a kerosene flush might "get" things that a a normal flush or a normal detergent oil might not. Sort of like radiator cleaning. You can drain the coolant out and it looks as clean as it could possibly be. Then you put straight water in and run it for a while, and you drain it out and you see stuff in there. The different viscosity of the water versus the coolant forced the flow to change just enough to sweep debris from places it gets trapped.

Same with kerosene, I'm guessing. It is different enough from engine oil of any viscosity that it can creep into places the oil never would and its solvent action can dislodge things oil never would. Further, it might dissolve the oil film on the carbon/sludge/chunks of stuff so that when the engine is refilled with oil, it can work back in and its detergents would have a fresh surface to work on.

I guess the way to "prove" this would be to change the motor oil a few times in succession so that the oil drained out is as clean looking as when it went in. Then do the kerosene flush. If it comes out clear, then it probably isn't necessary. But if it comes with "stuff" in it and looking darker than it ought to by simple dilution of the residual oil, it is doing *something*. Whether that is harmful, beneficial or neither is a different story.

I would, however, never run the engine with just kerosene in it. Spin it with the starter and the spark plugs removed (reducing stresses on the bearings to almost nothing) a couple of times, and then refill with oil and do the same, and then drain and refill again with clean oil, before I ever started it.

The only risk I can see is that if there is enough gunk in the engine, it might clog return passages and you could end up with oil pooling in odd places. I guess if one was really nuts, they could hook up a pump that forces the flush product up through the oilpan drain plug and catches the outflow out of the oil fill hole. That would be a heck of a project, but could be a way to resurrect an engine that might not be worth tearing down. The subsequent draining of all the kerosene and emptying the cylinders and all that would take forever though.

 

[ac_tc]

Kerosene, diesel, lamp oil....
I cant imagine any reason to fill the pores in your bearings and bores with something that actually destroys your oils ability to lubricate!
Even Harley mention this in their FSM:
Clean the cylinderwalls with soap and water not kerosene.
Rinse and dry. Kerosene stays in the pores of the cast iron and causes engine wear for a long time.

If i would get a serious coolant leak into the engine i would use thin oil, like 0w-20 or atf for rinsing the engine.
Start-run til warm-change...a couple of times

 

[Bruce T]

Ah, interesting point. I don't see any reason why solvents wouldn't dissolve the oil and additives coating the metal and then get into the pores.

 

[Bruce T]

My previous comments were based on approximately 1/2 quart remaining behind in the typical engine after draining the oil pan. Small amounts of solvent can destroy large quantities of oil. It's the same as the UOA standards for fuel dilution: 1% fuel is the warning level for oil and 2% is the condemn level.

If you follow ac_tc's logic, which I think is sound, then not only have you removed the protective barriers to the metal with an engine flush, but solvent in the metal pores will prevent new oil from establishing new barriers. There are many places were friction occurs in an engine, and the risk of wear is now high at these points.

 

[expat]

Originally Posted By: Bruce T
Ah, interesting point. I don't see any reason why solvents wouldn't dissolve the oil and additives coating the metal and then get into the pores.


Oh my God, solvent in my engines pores!
Time to get rid of my parts washer.

 

[expat]

Quote: [Small amounts of solvent can destroy large quantities of oil]

And remember solvent is often used in the refining process of motor oil.
Solvent will dilute, and reduce the viscosity of an oil, but will not significantly change it's lubricating properties once the solvent has evaporated.

Methinks that you are reading too much Additive sales hype!

 

[Gary Allan]

That level of flushing is after any and all other remedies (especially the Miyagi "best defense is no be there") are employed. If your best efforts failed, and the condition presented a problem, then sure. What do you have to lose?

If I was going to "setup" for this I'd be pumping it through the oil filter outlet point with a block adapter. I think the cartridge types may not be able to do this. I guess you could rig a dummy cap and leave the filter intact.

It would never be something I did as PM. I won't even use MMO for something like that.

 

[Bruce T]

There is another reason why they use soap and water to clean cylinder walls. After machining, solvent drives metal and abrasive particles into the pores, but soap and water doesn't. I don't know why. This is common engine building practice.

The critical question is how much the oil viscosity drops. It's true that a mild drop isn't an issue, but a large drop means the oil film can shear or evaporate at operating temperatures.

 

[expat]

When you Hone a cyl you use a honing oil, during the process you end up with a slurry of Honing abrasive and oil coating the cyl walls that needs to be removed. If you use a solvent, the oil/grit mix WILL be thinner, and you my remove a lot of it, but eventually the solvent will evaporate and you'll be left with a coating of oil an abrasive again.
Water and detergent breaks down the honing oil into an emulsion that can be washed away more thoroughly.
It's common to use a light oil or WD40 type spray, after washing to protect the newly honed cyl was from rusting at this stage.
Please forget the idea of steel being porous, unless you are talking about Oilite bearings engines don't absorb the way you see illustrated in some of the oil additive hype.

Quote: [The critical question is how much the oil viscosity drops. It's true that a mild drop isn't an issue, but a large drop means the oil film can shear or evaporate at operating temperatures.]

You should talk to Dr AE Haas about viscosity
Not all components of motor oil evaporate

When fuel dilution shows up in oil analysis, it is often a symtem of a chronic fuel problem that should be addressed. Typically raw fuel, washing the very thin layer of motor oil that coats the cyl wall.
Again if you need to understand how much oil can be diluted and still provide lubrication, Look at a Two Cycle engine!

 

[Bruce T]

Yes, your explanation does make more sense (why engine builders prefer soap and water, not solvent, for washing away every trace of abrasive grit, metal, and oil).

I'm not afraid of low viscosity oil, since I'm currently running 0W-20 grade oil in a Civic Hybrid. Most people worry when the oil viscosity falls out of grade. For a 20W at 100°C, this is below 5.6 cSt. With the typical 20W starting out in the 8's, I would personally get uncomfortable below 7. I'm not saying there isn't a margin of error, but I want that safety margin. I do lean in the same direction as Dr Haas, just not as far.

Manufacturers also talk about condemning an oil when the 40°C cSt viscosity loss is 15%, although Doug Hillary has argued that acceptable fuel dilution will vary according to engine design (Caterham brought this thread to my attention):

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1596214&page=all

Even when normal operating temperatures are held long enough to evaporate the high levels of solvent, there will still be irreversible chemical damage to the base oil and additives. There is no better solution than multiple oil changes at idle.

 

[expat]

Agree.
If you have, or suspect a sludge problem, don't run long OCI's.
If you use an oil Additive to resolve a problem, Don't run long OCI's