Oil Change

Synthetic oil really do last that long... don't worry about it. I would say

12,000 miles is the maximum I would go with any synthetic oil. The new engine nowdays are very very clean burning engine so there is not much impurities ends up in oil.

If you feel more comfortable with twice a year interval, then you can request it at the dealer... although you will have to pay for that service.

I personally are running synthetics on all our cars now and changing them once a year. Older cars such as older than 1990, I'd probably will change it every 6 months because the filter are not designed for such longer intervals.

Why this arbitary figure of 12k miles? Is there not an 'intelligent' service monitor and indicator system fitted to the 2003 E320? If so, why question its advice?

The whole system was designed for a shorter service interval. Go with the recommendation as written in the manual.

Huw

The monitor service is excellent advice... most people would end up changing their oil at about 10K miles.

The 12K miles figure I came up with is because of an independent lab oil test result I read at Amsoil... it stated that most oil will last about 12K miles... maybe a bit more... but at that time, the protective additives are pretty much gone.

Amsoil however claims their oil last 25K miles... because of their higher additive contents... hence cost more.

My diesel ML270 did about 14000 miles changing by monitor.

Simplistic and mistaken. There are so many variables between engines, operating conditions and oils that a blanket statement is meaningless.

"The additives are pretty much gone"? Gone where? Depleted? How so?

Higher additive content than what? If they have more additive then they have less oil, right?

Huw

Hey, You are right... there is alot of variables and MB service sensor is a great tool. I am not trying to say that 12,000 is definite limit for majority of synthetic oil. However, I am not ignorant like those greedy people who says change your oil every 3000 miles... dino or synthetic. That's a waste of precious resource.

The additive get depleted to heat, wear and tear. It is not that oil that goes bad... that is why we recycle it... It is the additives that depletes over time and combustion waste that ends up in oil.

sensor

limit

The 'additives' do not get depleted in the sense that I think you mean. Think of a bowl of dirty dishes in a bowl of water and washing up liquid. As more and more greasy dishes get washed, the effectiveness of the soap diminishes but the soap is still prsent. It just gets saturated with grease. The same goes for oil. It gets saturated with contaminants. However, some grades of oil can withstand much more contamination than others while remaining effective, in the same way that Fairy does more dishes than BrandX. Oil is also subject to degradation from heat and pressure stress. The resistance to these is mainly dependant on the quality of base oil and this is where synthetics tend to excell. It should be pointed out that though synthetics might excell at this feature, the saturation properties described in the first paragraph are totally independant and may vary as much between synthetic grades as between mineral grades.

It is not that

additives

Actually the oil does degrade substantially. It may completely lose its viscosity, for instance, because it has lost its shear strength property due to high shear forces in valve gears for instance. Oil is recycled but this process may need the complete re-refining of the oil as if it was virgin crude.

Huw

Excellent info... thanks for reminding me... just too many things in my head.

i OWN A 1997 e 320. I change the oil every 3500 miles and only use Valvoline 10-30. I think 10,000 is a long time between changes.

gene

Why?

You must have a trip computer or service booklet that tells you when to change oil.

DAS