Another use for Diesel Fuel?

[Guest]

I was reading the tech section of the June 08 issue of Rider magazine when I was surprised to read the following:

"That same old-school mechanic I worked for in high school used to let a car idle for an hour or two with a crankcase full of diesel fuel to clean up the engine internals. Judging by what came out when he had me drain the crankcase, it worked pretty well."

This is totally out of left field to me-I would have thought that there was not enough lubrication capacity in diesel fuel to risk doing something like this. Has anyone experience with this?

[Billy Ricks]

I was reading the tech section of the June 08 issue of Rider magazine when I was surprised to read the following:

"That same old-school mechanic I worked for in high school used to let a car idle for an hour or two with a crankcase full of diesel fuel to clean up the engine internals. Judging by what came out when he had me drain the crankcase, it worked pretty well."

This is totally out of left field to me-I would have thought that there was not enough lubrication capacity in diesel fuel to risk doing something like this. Has anyone experience with this?

I always had the feeling that the crankcase flush additives were nothing more than diesel or kerosene. I can see adding a quart or so before an oil change and letting it cycle at idle, I'm not sure I'd use straight diesel though.

[trippivot]

kerosene, marvel mystery oil, diesel fuel, Gasoline, theory is to dilute the oil and remove sludge. right?

[Nessism]

The bike I just bought had a goodly bit of gas mixed into the oil. Ran the engine briefly and drained it out – oil came out black as coal. Not sure using flush additives are good though since portions of the thinned oil mixture stay inside the engines various pockets and such – like the valve pockets. Honestly though, if you are taking care of your engine properly there should be no need for any kind of engine flush treatment. If the oil is black, put the bike on a 1000 mile oil change interval for a few changes until things clean up. Much less risky way to clean the engine in my opinion.

[Dan Ruddock]

The right way to do it!!!! Great product that made a real difference in the way my TDI runs. I am not the snake oil type but this one is an exception. All of the guys at (bob is the oil guy) site love this stuff. Dan

http://auto-rx.com/index.html

[tone]

Diesel is a good cleaning agent if used to soak parts, but thinking about this a little makes me think running an engine full of diesel is a very bad idea

diesel needs heat & compression to ignite i suspect there could be enough of both produced in the crankcases to cause a big bang

[Ghostgs1]

I've not done this, but I have seen others get away with it. Kind of a scary approach to internal cleaning, but it appears to be effective. Ray

[rustybronco]

No experience with a crank case full of diesel and personally I wouldn't try it.
long ago we use to mix 1 quart of no.1 fuel oil with 4 quarts of engine oil in our cars to thin out the oil in very cold weather, in order to allow the engines to crank easier at low temps. it never hurt the engines we did it on.
I imagine a small amount would help clean a engine.

[GS1100ez]

ive heard of draining out some oil, 1-2qts and then putting in ATF of what you took out

atf has detergents in it which clean stuff out, so you let it run or drive it around for an hour or 2 and it will clean it out

atf is also around 15weight, so it will provide some form of close lubrication


i use diesel engine oil in my jeep
it has detergents aswell
oil is always black when i change it every 3k

took the valve covers off to redo the valve seals at 250k head was clean as could be under the cover, no sludge or anything


i do sometimes mix in some marvel mystery oil in the oil, i do put it in every couple tanks of gas too stuff works good

[SqDancerLynn1]

As far as your GS do not put anything in the crankcase except oil !!!! NO additives or you may damage the clutch
Deseal may clean but any crap ends up in the oil pickup. If bad enough?? NO oil pressure

[Clumzi]

There is also the assumption going around here that black oil necessarily equals cleaning. If you are mixing chemicals around your engine, the heat and constant blending may simply cause a chemical reaction that darkens the diesel/diesel gas mix and is mistaken for "cleaning". Does it really clean anything? Does the product really make the machine run better? If so, is it because of cleaning that was going on or something else? Is it hopeful thinking or a placebo-esque sort of thing?

I like Ness' comment. Oil looks dark? Change it every 1000 miles until it starts looking cleaner. -nick

[Clone]

I would use a half oil half diesel mix to clean out the engine on farm equipment that had sat for a while. But only to run for a few minutes, like less than ten. Idling for 2 hours with only diesel in the engine is a sure way to wreck the bearings or spin one or two. Diesel has some lubricating properties, but not enough viscosity(?) to provide any real protection, remember it is just a little thicker than gasoline, and thinner than 0W. As a flush OK, but as a lubricant for 2 hours NO.

[Planecrazy]

Not that I'm suggesting this, but if you WERE going to do something off the wall like use diesel instead of motor oil you'd be better off using biodiesel, because it is a much more effective solvent AND it has much better lubricity than petrodiesel.

Having said that, I wouldn't do it...

Regards,

[Old Colt]

One needs to remember that a few decades ago engines needed to be flushed out occasionally. Oil packages broke down quick and ring seal was marginal at best. But we have seen a bit of a change with engines and lubricants over the last 30 years and we do not get the sludge buildup anymore. Heck I have engines with 150K on them that the oil is still golden through the full change period.
But 2hrs with straight diesel, that is not to smart. Some dilution for a short run, yah that is fine.

Way back in 1980 when I changed my 550 over to run Castrol R I had to wash out the engine to get all the mineral oil out and used straight kerosene for the flush . If I recall I ran it but not for long. At that time Mobil 1 was just introduced, many shied away from it then. Now look at the synthetic world. Like I said, the lubricants have changed.

[Dave8338]

If you have a roller crank you won't see any problems there. The only area that I would worry about (for a short run/flush would be the cams...a long way from the pump, many areas for the diesel to leak past on it's way the the cams, and no replaceable bearings if something does score.

Two cycles run just fine at a 40:1 mix and I've run them for 8 hours at a crack on more than 50:1 and have never seen a problem. Granted they have reed valves and no cams, but the rest of the "up and down" junk is the same...