Diesel Engine Wear

[SkyPup]

75% of all diesel engine wear occurs at start-up, and 75% of that is where the most friction occurs -> in the rings and cylinder liners.

The limiting factor on the life a diesel engine is the cylinder bore, once the bore is shot, a rebuild is on order.

Wear can occur on any of the surfaces in relative motion, ie. piston bearing sufaces, bore, rings, grooves, vavle train, main and big eng bearins, as well as camshaft bearings. However, the most important wear that determines how long the engine can be run between overhauls is mainly that of the bore at the upper limit of the top ring travel, the radial wear of the top ring with resultatn increase of ring gap and consequent blowby, and the increase of side clearance of the top ring due to ring and groove wear. This wear is due to abrasion by engine deposits or by foreign matter that enters through the air intake or crankcase breathers. Abrasion by engine deposits usually increases with an increase in the severity of operating conditions, however that due to adventitious matter is usually indepent of operating conditions.

Provided that air filtration is satisfactory, the MAIN CAUSE of cylinder bore or linear wear is the corrosive action of inorganic acids derived from SULPHUR IN THE FUEL.

The MAIN PROBLEMS that arise in the lubrication of diesel engines come from the deposits arising from the combustion of the fuel and the lubricating oil, and from the partial oxidation of the lubricating oil.

The quality of lubricating diesel oils has increased exponentially over the last twenty or so years, while the quality of diesel fuel has dropped like a rock.

The deposits on the piston crown are derived mainly from the fuel with a contribution from lubricating oil additives other than ashless additives. Top land deposits are both from the fuel and the oil.

The BEST thing you can do for your TDI is to use high quality diesel fuel with the lowest possible sulfur content, lowest possible aromatic content, and a minimum cetane value of 50 to keep combustion deposits minimized. In addition, a high quality full synthetic oil with ashless additives can help with keep the rings free from deposit packing if the ring groove temperatures are excessive, ie above 250*C. Stationary diesel engines and marine diesel engines operating at constant loads for long periods of time have ring temperatures not exceeding 220*C and under these conditions ring-groove deposits are NOT a problem.

Get some top notch engine oil and use only top notch diesel fuel if you want the best for your TDI engine!

Remember, the fuel quality is even more important that the oil quality.

 

[SkyPup]

AMOCO PREMIER #2 MINIMUM 50 CETANE <300ppm SULFUR

Swedish diesel fuel is the highest standard quality in the world with the lowest sulfur content to date, and it is easy to see, that the particulate matter is MUCH LOWER than even the standardsvery high quality European diesel fuel (which is 50 times better than the crap diesel fuel in North America) supply when used in a VW TDI engine, resulting in MUCH LESS ENGINE DEPOSITS.

USE GOOD DIESEL FUEL AND GOOD OIL and you can ride forever!

LOL

[ August 31, 2001: Message edited by: SkyPup ]

 

[SkyPup]

Don't leave home without it!

 

[Turbo Steve]

Great post Thom:

Besides engine coldstarts with Boundary Lubrication, wear also comes from dirt, and driving style or conditions.

Last of all, the choice of a diesel oil to avoid grinding your camshaft to powder.

-Steve

P.S. Do they make any silver shoe polish? I'd like to give my cam a good going over before Pete takes a look at it!

 

[SkyPup]

Engine Manufacturers Association says exactly the same thing:

Piston Deposits
Buildup of ring belt deposits has been found in service experience to cause improper ring operation which can lead to high oil consumption and cylinder scuffing. This condition generally determines the life to overhaul for most diesel engines and may have an effect on emission levels. Two engine tests have been identified to measure this performance requirement. The Caterpillar 1K test is used for evaluating piston deposit control in engines equipped with aluminum pistons, while the Caterpillar 1P test is used for ferrous pistons.


Wear - Ring/Liner

Piston ring and cylinder liner wear are directly related to engine service life. Under conditions of retarded fuel injection timing, used to meet reduced exhaust emission limits, fuel soot induced wear is likely. The capability of an engine oil to protect the piston rings and liner under these conditions is evaluated with the Mack T-9 test.

Wear - Valvetrain

Increased valve train loading, coupled with higher engine oil soot loading, as a result of engine design intended to meet reduced exhaust emission standards, has created a concern over excessive valve train wear. Wear of these components may change engine timing, impacting performance and exhaust emissions. Wear also shortens engine life.


Valve train wear mechanisms may be either rolling or sliding depending on design. The Roller Follower Wear Test (RFWT ASTM D5966) is used to measure engine oil performance for its effect on axle shaftwear, indicating roller wear conditions, the M11 High Soot Test (M11-HST) evaluates wear of valve train components under sliding conditions. Both tests are necessary to properly measure all valvetrain wear.

http://www.engine-manufacturers.org/about/emalrg1.cfm


For the Global DHD-1 High Performance Turbocharged Diesel Engine Oil Specifications and Tests, click here:

http://www.engine-manufacturers.org/about/globalDHD_guidelines.pdf

 

[SkyPup]

 

[mickey]

1. Use a high quality synthetic oil, preferrably with a high Group V content.

2. Add Moly Disulphide.

3. Use a bypass filter.

4. Send angry emails to the EPA.

That's my plan of action!

-mickey

 

[GeWilli]

mickey - wouldn't #1 preclude using anything other than the evil S3000 stuff? I don't think the M word boys have as much Group V base stock in their thick stuff . . .

 

[Hyates]

Justme: Our old '87 Golf Diesel (1.6L non-turbo) didn't consume more than 1/2 litre of oil between changes (6000 km or 3600 miles). Sold the car with 275000 km (171000 miles). Oil consumption was constant throughout the 12 years we owned this car.

Harry.

 

[Hyates]

Idling causes wear as well.

Diesel engines idle at a cold temperature. Thus blowby, unburnt fuel occurs, thus SOOT. This causes possible metal wear.

As noted by Finning Oil Lab.

Harry.

 

[tasma]

It would be interesting to find out what UPS has learned about engine wear. Their drivers are required to shut down the engine at every delivery. I am wondering if short stops do not allow the oil to drain off the engine parts.

Has anyone done oil analysis on a TDI that has run on nothing but bio diesel?

 

[SkyPup]

Excessive oil consumption due to excessive oil blowby is the final kiss of death to any diesel engine. Sometimes the oil consumption may be due to turbocharger wear, however, it almost never is due to valve or valve guide wear since you need a vacuum to draw the oil into the intake tract and our TDIs operate without any vacuum.

Any engine that has used inferior oils and fuels (like Ric's) is going down for a rebuild sooner than someone who uses superior oils and fuels.

 

[justme]

The old 1.6L non TDI diesels definitely consumed oil because of worn valve guides though.

 

[tasma]

I took the oil filler cap off my 240D Mercedes and watched the oil pour out onto the cam. I did a cold start after the car had set for 24 hours. It took 4 seconds for the oil to start pouring out onto the cam. And this is with 0W30 oil!! It was really surprised at this. Watching the cam spin that long without oil was a real eye opener.

 

[mickey]

GeWilli: Why...yes! By golly, it would!

-mickey

 

[justme]

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Justme: Our old '87 Golf Diesel (1.6L non-turbo) didn't consume more than 1/2 litre of oil <HR></BLOCKQUOTE>

One of our A1s (I think it was the '80) definitely started to drink oil, and the mechanic said it was the valve guide for sure, that they were known for that.

I also wonder whether short stops cause as much wear. I'd imagine the cam at least, if not also the cylinder walls, would benefit from a residual film -- maybe especially if you're using a "thicker" oil. However then it's a bit slower to get going as well.

Today we took the '96 out for some errands. We must have started/stopped the engine 20 times in the course of 4 hours.

 

[jhedrich]

I am equally intrigued by the amount of wear that happens in an engine and how concerned everybody is about engine wear in the forum.

Let me ask this. Let's say we don't ever change oil in our engine, just the filter, which do you think is going to wear out first and cause us to discard the vehicle in favour of a new one: the chicken $#!t plastic dashboard or the high tech engine?

I think the longevitiy of the engine compared with every single other component on the car is the least of our worries, and probably not that expensive when you start pricing out replacing seats, steering wheels or odometers if those items should wear out before the engine! OH MY!!!!!!!!!