(02-01-2011, 04:30 PM)yankneck696 but much more longevity out of the Mercedes.

(02-01-2011, 05:26 PM)mantahead Both VW diesels and Mercedes diesels experience very little wear on full synthetic- either will easily last over a million miles in most situations.

The VW diesels just seem to have a particular problem where carbon builds up behind the rings, presses them out into the bores, and destroys both the rings and bores in short order. This problem is 100% eliminated on synthetic oil- people have torn down VW diesels with over 300k miles on synthetic and found no measurable wear. The rest of the VW engines (bearings, etc.) wear just as well as Mercedes engines, even on non-synthetic.

I don't understand why VW diesels have this problem, and Mercedes do not- but I doubt it has anything to do with the weight, size, or power output of the engines.

(02-01-2011, 08:09 PM)DieselSchlepper You could try changing oil - a slightly heavier weight.

(02-01-2011, 05:58 PM)casioqv Wayne- the grammar in your post is very confusing to me, but you might want to try your question on a TDI forum like tdiclub.com.

Sometimes when VW diesels are just beginning to suffer symptoms of low compression from stuck rings, the condition can be still be remedied by switching to synthetic oil and running the engine hard whenever possible. Smoke when cold can be caused by other things also- worn injectors, improper injector pump adjustment, etc. Most of my knowledge pertains to the older IDI engines.

(02-01-2011, 02:24 PM)DieselSchlepper ... IN the US the failure rate was high on the narrow cam lobes, everywhere else almost nonexistent. One of the problems in the US is that everyone has trouble understanding that if VW specifies 505.0x oil they mean exactly that. ...

(02-02-2011, 03:59 PM)DeliveryValve I am in the camp who believes changing oil early on a TDI or even a Mercedes CDI will cause more wear then keeping it in for 10,000 miles plus.

(02-02-2011, 04:21 PM)casioqv ...

I think that's true with most engines... oil analysis of metallic wear generally shows higher wear rates for the first few thousand miles after a change. 15k mile+ change intervals on group IV synthetics are probably ideal for minimizing wear; perhaps much longer if an oil analysis shows the oil to still be functioning properly and isn't experiencing fuel dilution, etc....

(02-02-2011, 05:29 PM)ForcedInduction Thats fairly difficult to convince of anyone in the USA since the average person does only 13k/year.

Combined of my two cars, I only drove 9,160.7miles last year. If I were to go by your suggestion of 10-15k on synthetic, my 300 would see an oil change every other year and my 240 once every 3 years! Once/year for both is fine.

(02-02-2011, 09:44 PM)DieselSchlepper Now that's an interesting thought that flies in the face of conventional "wisdom". Longer oil change intervals leading to less wear.

(02-02-2011, 10:18 PM)casioqv ..... I have no idea what the underlying mechanism is here, however. .....

Quote:STOP STOP STOP!

The ORIGINAL factory APPROVED oil change interval is 30,000 miles! YES 30,000 MILES!!

Did you comprehend that?

THE ORGINAL OIL CHANGE INTERVAL APPROVAL IS 30,000 MILES!!!

Now that I have that off my chest,

VW reduced the interval from 30,000 miles to 10,000 miles in the US market...any guesses why?

Because people like you either:
1) Can't read the owners manual
2) Don't trust the car makers
3) Can't follow directions
4) Fail to adhere to the service indicator in the car

VW does NOT want oil change intervals of less than 10,000 miles due to how the oils function in the engine, shorter intervals INCREASE WEAR, Don't argue with me about it, if you take the time to track wear rates during an oil change at 250 mile intervals you can plot the reduction and stabilization of the wear rates out beyond 25,000 miles!

Think of oil as having 2 types of wear reducing additives, the first provides protection by/thru detergancy (cleansing of internal surfaces), dispersing soot, neutralizing acids (not an issue now with ULSD), and several other types as well. These additives are generally very specific to diesel engines and must pass specific tests in VW Diesel engines.

The next type of additive is a wear additive. These protect the engine where the thickness of oil may be too thin to prevent metal to metal contact. Other additves in this type range also provide protection to the cam and lifters, engine bearings, piston wrist pins etc.

Now pay attention, the 2nd group of additives account for less than 3% of the total volume of the oil. These additives also account for 90% of the engines oil protection! These additives require heat and pressure to bond with the critical wear surfaces, but due to the low percentage of additive in the oil they require time to fully place on those surfaces by the pressures of the component they are protecting. Example, an engine at operating temperature at the point where the cam presses on the lifter generates in excess of 90,000 psi, that pressure and the heat of the engine causes the 3% portion of the 1 micron thick oil film to form a crust or sacrifical layer at the point of contact. Since only 3% of the oil contains the wear additives, it requires hundreds of thousands of passes to generate a sufficient film to stop the wear at this specific point in the engine.

Everybody is quick to make the arguement that the old oil had these additives so they are already in place, right? not quite!

Remember the first type of additive? In that 1st group you had "detergents" that cleanse the inside of the motor. These cleansers are used up very rapidly after an oil change since they attack the remaining oil that was left after the oil change. These cleansers if you will also reduce the effectiveness of the high pressure wear additives...See where this is going?

Before explaining further, after that initial period the dispersants in the oil work to prevent the adhering of the particles in the oil to any of the internal surfaces. These additives are often unique to diesel engines are also the reason why the oil looks so black so quickly, they are doing their job by preventing the soot from building up in any one place instead they are dispersed in the oil evenly throughout the oil sump which prevents sludging and other contamination related issues.

Back to the detergents and the high pressure additives, the layers of high pressure additives leftover are not being replenished after the oil change due to the cleaning process that is going on with the new oil to neutralize the remaining acids, and other contaminants in the engine. As the cleaners in the oil are used up in the first 500-1000 miles, the wear additives are able to re-generate a protective layer in the engine that stops the wear at that location.

You break down the oils life cycle like this:

Phase 1: Detergants attack the internals removing accumlated contaminants, neutralize acids and force those into suspenstion in the oil. This period of time lasts between 500-1000 miles

Phase 2: During the first 1000 miles the oils viscosity provides the majority of the wear protection by virtue of the film it creates on the surfaces. This phase generates relatively high wear rates but due to the short duration this is accepted due to the removal of contaminants that could result in long term damage to the motor. Wear rates in the period of time are generally speaking 5-10ppm per 1000 miles.

Phase 3: Detergents are now used up and the oil additives are forming their protective layers in the "extreme pressure" regions of the motor. Now the oil additives are working in conjunction with the oil film and the wear rates drop from 10ppm per 1000 miles to around 1-2ppm per 1000 miles.

Phase 4: Longterm peace! The oil is operating in a period of equilibrium, the wear additives are placed, Oil viscosity is in perfect range for the engine, Dispersants are continually working to prevent soot and other contaminants from accumulating on the surfaces and wear rates remain between 1-3ppm per 1000 miles.

Phase 5: Oil run out, the oil during this phase begins to increase in viscosity (or thin in some cases), Extreme pressure additives begin to lose effectiveness due to increased concentrations of wear particles (VW tests out to 8%, most oil changes never see in excess of 2% after 30,000 miles). This is when you begin to see a rise in the wear metal formation in the engine. Often wear metals during this phase rise to the 3-8ppm per 1000 mile range. Notice that the wear metals being generated are still LOWER than they were in the first 1000 miles?

--------------------------------------------------------------

When somebody says they are going to change the oil every 5000 miles or twice as often they are DOUBLING the number of detergent cycles and DOUBLING the number of cycles where the engine is running at it's highest wear rates!

PPM/Fe (generation of Fe in 1000 mile increments)
Short drain intervals
1K oil change
10ppm = 10ppm in 1000 miles = 10ppm/1000 miles

3K oil change
10+2+2 = 14ppm in 3000 miles = 4.6ppm/1000 miles

5K oil change
10+2+2+2+2: Change oil = 18ppm in 5000 miles = 3.6ppm/1000 miles

Long drain intervals
10K oil change
10+2+2+2+2+2+2+2+2+3 = 29 ppm in 10,000 miles = 2.9ppm/1000 miles

15K oil change
10+2+2+2+2+2+2+2+2+3+3+3+3+3+3 = 44ppm in 15,000 miles = 2.9 ppm/1000 miles

20K oil change
10+2+2+2+2+2+2+2+2+3+3+3+3+3+3+3+3+3+4+4 = 61ppm in 20,000 miles = 3.3ppm/1000 miles

When ppm of Fe per 1000 miles reaches 5-7ppm per 1000 miles you can consider the oil ready for a change...

The above is based on real world TDI oil samples.

I have personally used up to 25,000 mile oil drain intervals on my TDI and still never reached the 5-7ppm range! I changed it at that time due to soot and TBN depletion (high sulfur fuel at the time).

Anybody that tells you that short oil drain intervals are good for your motor don't know what they are talking about!

(02-11-2011, 07:29 AM)DieselSchlepper What about changing the filter at shorter intervals?

(02-11-2011, 07:29 AM)DieselSchlepper Sounds good to me. I'm sure there is disagreement over that though. I think I'll go with the OA on mine at 9K miles and see what it says. What about changing the filter at shorter intervals?

(02-01-2011, 03:08 PM)casioqv Yea, the Mercedes timing chains aren't that difficult to replace, just more so than some timing belts. The TDI timing belt is actually harder...