[aaccon]

Hi,

I came across an article discussing the `drawbacks` of replacing the oil too often in a diesel car. I had not heard of this before and was wondering what fourm members thought.

Listed below is the article concerned:


Quote:

engine oils (particularly diesel oils) contain detergents to clean the inside of the engine. The idea is that as the oil runs around inside the engine it picks up any foreign matter, soot particles and dirt, and these are trapped in the oil filter. By their very nature, detergents are "unstable" chemicals - in the sense that they have a basic pH and are corrosive. It is well known that alluminium alloys are easily corroded by basic solutions - an extreme example can be seen by placing some aluminium foil into a solution of drain cleaner (sodium hydroxide). The aluminium will quickly dissolve and there is even a fun release of hydrogen gas.

There are many, many aluminium parts in the modern vw diesel engine, and anything that comes into contact with coolant or oil is going to be susceptible to corrosive wear if the oil or coolant is basic. This is why coolant is mildly acidic (if your ever unlucky enough to get it in your mouth you will taste it, but it is also poisonous).

The important part is that if the interior of the engine is a little dirty, then the detergents in the oil are "used up" over time - like if you only add a little dishwashing detergent at the start of a big wash and never add any more, eventually the ph of the water goes back towards neutral and the suds dissappear - you need to add more detergent to keep washing the dishes. in the same way, it is by design that the engine oil runs out of detergents a certain way into its life cycle, so that no corrosive wear can occur. This is why if you lived in inner city sydney, you wouldnt use diesel engine oil in your petrol car, but perhaps if you were a farmer, you could with no ill effects, because the operating environment of the engine is so bad that it literally gets very dirty (inside and out - air cleaners can only do so much).

Having said all that - everything in moderation. I generally used to change the engine oil about every 5-6000km, now the oils are so good and I am using fully synthetic, I change it every 10-12000km.

Any opinions ?

Thanks

[samchuang33]

Originally Posted by aaccon

Hi,

I came across an article discussing the `drawbacks` of replacing the oil too often in a diesel car. I had not heard of this before and was wondering what fourm members thought.

Listed below is the article concerned:


Quote:

engine oils (particularly diesel oils) contain detergents to clean the inside of the engine. The idea is that as the oil runs around inside the engine it picks up any foreign matter, soot particles and dirt, and these are trapped in the oil filter. By their very nature, detergents are "unstable" chemicals - in the sense that they have a basic pH and are corrosive. It is well known that alluminium alloys are easily corroded by basic solutions - an extreme example can be seen by placing some aluminium foil into a solution of drain cleaner (sodium hydroxide). The aluminium will quickly dissolve and there is even a fun release of hydrogen gas.

There are many, many aluminium parts in the modern vw diesel engine, and anything that comes into contact with coolant or oil is going to be susceptible to corrosive wear if the oil or coolant is basic. This is why coolant is mildly acidic (if your ever unlucky enough to get it in your mouth you will taste it, but it is also poisonous).

The important part is that if the interior of the engine is a little dirty, then the detergents in the oil are "used up" over time - like if you only add a little dishwashing detergent at the start of a big wash and never add any more, eventually the ph of the water goes back towards neutral and the suds dissappear - you need to add more detergent to keep washing the dishes. in the same way, it is by design that the engine oil runs out of detergents a certain way into its life cycle, so that no corrosive wear can occur. This is why if you lived in inner city sydney, you wouldnt use diesel engine oil in your petrol car, but perhaps if you were a farmer, you could with no ill effects, because the operating environment of the engine is so bad that it literally gets very dirty (inside and out - air cleaners can only do so much).

Having said all that - everything in moderation. I generally used to change the engine oil about every 5-6000km, now the oils are so good and I am using fully synthetic, I change it every 10-12000km.

Any opinions ?

Thanks

Interesting...

I usually change my diesel engine oil around 15000ks even though the car said it should be ok till 20,000ks. I think changing at every 5000-10,000ks is a bit too much but leaving it to 20-30,000ks is too long too. Sometimes, it could take over 18 month for some owner to clock up to 30,000k for a service and i think engine oil will degrade significantly after 12month so my opinion 15,000 is a good average.

BTW, where did u find that info from?

[aaccon]

Hi samchuang33,

It was posted on the VW Watercooled forum

http://www.vwwatercooled.org.au/f77/...out-45648.html

Not being a mechanic or overly motor savvy I was interested in hearing what members of this forum thought - especially when VW/AUDI/BMW are similiar league of vehicles.

Cheers..

[samchuang33]

Thx for link. It was very informative.

I guess that changing every 15000 is still good from what they r saying. I did my first oill change for my 330d at 7500k and plan to do another one at 17500ks. After that, i will just get it service every 15000ks even thou computer said that it will last till 30000ks. When u pick up ur car, u will notice that the new LCI e90, there is a service check program in the car at 15000ks anyway, so it probably a good idea to get a oil change when they do the program check if u want.

I think BMW is really stretching the service interval too long for diesel cars to stay competitive in the market. Diesel has alway needed more service compared to petrol and servcing them at the same milage is risky. Better to be safe than sorry i guess especially when if u push ur car often.

When is u car coming mate?