Author Topic: Oil  (Read 11951 times)

aqmxv

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Re: Oil
« Reply #15 on: November 22, 2006, 02:02:04 AM »
Bill,

My understanding of the differences between an engine oil primarily for an otto cycle gasoline engine and that for a diesel is that:

1) gasoline burners get lots more moisture into their oil, and also often get sulfur or chlorides (as salt dissolved in water) in the gasoline.  The result is acidic products of combustion along with water in the crankcase - bad news.  Accordingly, gasoline engine oils tend to have elaborate buffer systems designed to neutralize the acids as they arrive in the crankcase, along with anti-foaming and anti-emulsion additives designed to do as much as possible to make sure that the water goes away quickly when the oil gets hot enough.

The other worry back in the day was dilution with fuel, but the advent of closed-loop fuel management systems and port fuel injection has mostly made that one disappear.

2) diesel engines run lean 99% of the time and the fuel is injected near the middle of the chamber - a long way from the piston rings.  So the whole combustion event also happens a long way from the rings.  The result is that there is much less moisture getting into the crankcase.  There's also less attack of the oil film on the cylinder walls, which contributes to the long-life reputation of most diesel engines.  The fuels may (previously) have had a lot of sulfur in them, but diesels tend not to let many combustion products into the crankcase.  Also, diesels tend to run hotter down below than gasoline engines, which, again, improves moisture boil-off.  The result is that oil has a pretty nice time in most diesel engine crankcases.  The additive packages do have some buffers to deal with sulfuric acid (much less deadly to metals than halogen acids like HCl are), but most of the additives are extreme pressure additives (like ZDDP) and lots of detergents to keep the soot in suspension so that the filter system can get to it.

Accordingly, you have a class of premium diesel oils out there sold for "million-mile" use.  Basically, you just test them for additive package breakdown periodically, and change them when the oil finally gets worn out at some very high mileage.  The engine will burn enough oil to require top-ups which replenish the additive stock significantly. 

There have been moves to do this sort of thing with gasoline engines, but generally the upper end of life for oils in gasoline engines is in the 500 hour range with a really large variation depending on engine design and drive cycle.  You end up spending a fair amount in lab charges to do the testing frequently enough to catch the oil degradation before something starts eating your chevy from the inside.  On something like a Cat or Cummins in a road tractor, you have gallons of oil in there and expensive filters, so changing is a much more expensive proposition and testing charges become a relatively smaller cost.

Generally, though, most oils for light-duty diesel use look a lot like oils for general automotive use.  Sure enough, a lot of oils are rated both for S and C class service, though usually to different severities of rating.

« Last Edit: November 22, 2006, 02:58:24 AM by aqmxv »
6/1 Metro IDI for home trigen

Doug

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Re: Oil
« Reply #16 on: November 22, 2006, 02:20:21 AM »
Considering what a litre of oil costs and the havock it can reap I have a few thought of my own to share....

I always believed diesel detergent oils were the best choice for air cooled engines and splash lubed engines with no oil filter should have their oil changed as regular as 20 hours. This worked out fine for me for years and years.

I use 15/40 in everything and it works....

Now I have a water cooled Petter with a lot of surface area and little chance of shedding the moister from the oil. Oil that doesn't get hot will have a short life in an engine....

An engine that doesn't get hot also won't need a multi viscosity so mono grades make more sence

Your not wasting oil if you cut it into your fuel stock so even at $4.00 a litre its still cheap to change it often.

Lastly detergents. Most engines of this era including my Petter call a flushing oil every so many hours because the oils of the day gummed and coked rings. Modern oils are designed to prevent this. The important thing to remember is all that material is held in suspension untill you change your oil ( or filter it out ) and it going wear things. Acids eat bearings enough said...

Change your oil often..........

Doug

SHIPCHIEF

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Re: Oil
« Reply #17 on: December 11, 2006, 05:11:32 AM »
Hotater mentioned that water sticks together with carbon to form that glop.
You need to heat up the oil to drive off the water and Filter the oil to catch the carbon.
If your engine has an external oil pump, you could run the oil discharge tube up around the jacket water outlet line, thru a spin on filter, and then into the engine. Manually stroke the pump before initial start up to refill the longer oil line.
Then I think Guy and I would be in agreement that the newer diesel mono grade oils available in any auto parts store would be fine.
I think 15-40 and 20-50 would be ok as well, but that's just me.
I built this into my twin, but I naturally did it the hard way. Looking back I could have done it much easier. Anyway, after a few minutes running, the crankcase is hot to the touch and the oil is just a few degrees below the jacket water temp, so 185 F should be about perfect?
Scott E
Ashwamegh 25/2 & ST12
Lister SR2 10Kw 'Long Edurance' genset on a 10 gallon sump/skid,
Onan 6.5NH in an old Jeager Compressor trailer and a few CCK's

biobill

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Re: Oil
« Reply #18 on: December 11, 2006, 01:06:47 PM »
 Sounds pretty neat Scott. Got pictures?                Bill
Off grid since 1990
6/1 Metro DI living in basement, cogen
6/1 Metro IDI running barn & biodiesel processer
VW 1.6 diesels all over the place
Isuzu Boxtruck, Ford Backhoe, all running on biodiesel
Needs diesel lawnmower & chainsaw

SHIPCHIEF

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Re: Oil
« Reply #19 on: December 11, 2006, 05:00:19 PM »
OK Bill!
I posted a Picture in the Coppermine gallery under SHIPCHIEF2
The heat exchanger is an oil cooler for a marine transmission, I got it on epay. The tube is 3/8 inch brake line from the auto parts store.
The plexiglas crankcase door was an idea someone on the list (was it Bruce or Quinn? I can't remember) thought up. I had a scrap the right size, so I made it. The dippers throw a sheet of oil around the inside that hits the 'window' about the width of the connecting rod bearing plus alittle wider. I think the oil gets thrown onto the thrust face of the cylinder pretty well so I don't worry too much about wrist pins and piston cooling.
I have a picture of my crankcase door oil filter in my first coppermine post. It is too wide, and the oil dipstick won't fit.
The oil dippers throw alot of oil at the camshaft. As the oil gets heated you can feel the block heat up under the cam ( and everywhere else)
Scott E
Ashwamegh 25/2 & ST12
Lister SR2 10Kw 'Long Edurance' genset on a 10 gallon sump/skid,
Onan 6.5NH in an old Jeager Compressor trailer and a few CCK's

biobill

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Re: Oil
« Reply #20 on: December 11, 2006, 10:29:26 PM »
Thanks Scott,
  Nice setup. I gotta have me a window!          Bill
Off grid since 1990
6/1 Metro DI living in basement, cogen
6/1 Metro IDI running barn & biodiesel processer
VW 1.6 diesels all over the place
Isuzu Boxtruck, Ford Backhoe, all running on biodiesel
Needs diesel lawnmower & chainsaw

SHIPCHIEF

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Re: Oil
« Reply #21 on: December 11, 2006, 10:48:20 PM »
I just used my window for a little while to see what the oil storm looks like. The crankcase vent is in the door, and I did not fit it to the window, so I ran the engine with the window nuts loose to let out any pressure. With clean oil and a bright light, you can see clearly what you always wondered about (in the engine) for a few moments before the oil starts to obscure the window.
I felt that the oil thrown against the door has enough impact velocity, and enough volume of oil to justify putting a pocket screen there. I think you could put some terrycloth towel strips in there and hold them in place with clips or a few magnets.
That was my first engine mod derived from conversations on this forum.
Hotaters filter was simpler, faster to build, and probably just as good; I just have to everything the hard way.
Jack certainly has more hours on his, I barely run mine because it's a standby power generator and source of entertainment.
Scott E
Ashwamegh 25/2 & ST12
Lister SR2 10Kw 'Long Edurance' genset on a 10 gallon sump/skid,
Onan 6.5NH in an old Jeager Compressor trailer and a few CCK's