Assumptions based on oil sump capacity?

[ttsakai]

Hi All-

Just wanted to query the expertise on this forum regarding assumptions or expectations one would make based on different oil sump capacities.

Here's what I'm thinking about. I have an AMG automobile and the engine has an oil capacity of 8 quarts (using Mobil 0W-40, not sure this is relevant). Noting that this is 3 quarts more capacity than the normal 5 quart capacities (or 160%) that other engines use, are there any conclusions one would come to?

Would the OCI be 60% greater than normal? ..., etc.

Just curious.

Thanks,
Tracy

 

[mechtech]

I used to work for AMG Mercedes, before being taken over by Mercedes.
Which has nothing to do with your question, except giving me status.
Larger oil sumps [whether trans or engine] take longer to get to operating or hot temps. You can extend the OCI because of the added volume of oil. The extra oil dilutes the contaminants, and the add pack doesn't get depleted as quickly. Also, with less general heat, there isn't as much breakdown in the oil.

 

[blupupher]

Who had the OCI formula here? One of the factors was sump capacity, so I would say yes, the larger sump would allow for the posibility of a longer drain interval.

 

[Tones]

quote:

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Originally posted by blupupher:
Who had the OCI formula here?

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That would be Tooslick. I think his formula is also on the Paradise Garage site somewhere.

Edit: found it here

 

[Kestas]

Consumer Reports listed the 1.8L turbo as sludge-prone in the Passat and Audi applications. Interestingly, the same engine is used in the NewBeetle, but not listed as sludge-prone.

A little investigating shows the only difference between the models is the sump capacity - 3.8 quarts for the Passat and Audi, 4.8 for the NewBeetle - even though it's the same engine.

The difference in sump capacity is due to the vehicle architecture.... transverse engine for the NewBeetle, north-south for the Passat and Audi.

 

[blupupher]

quote:

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Originally posted by Tones:

quote:

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Originally posted by blupupher:
Who had the OCI formula here?

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That would be Tooslick. I think his formula is also on the Paradise Garage site somewhere.

Edit: found it here

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Yea, that was it, Theory 5: Kublin Method.

 

[haley10]

Good link, Tones. Yep, to estimate oci, you need more than sump capacity. Power density, and total amount of fuel burned are factors. Can't really calculated based on sump size alone.

Mechtech is of course correct, all other factors being equal.

 

[Ray H]

Could the 60% greater oil capacity be construed as evidence that the engine in question might also be 60% "harder" on its oil than engines with less oil capacity over the same OCI?

 

[ttsakai]

Thanks for the interesting Kublin method reference. I used it as instructed to see what type of OCI it would generate (assigning Mobil oil a TBN of 8). Entering all the appropriate information and just changing the value in the oil capacity field between 5qts. and 8 qts. generated the following OCIs:

5 qts. 6,705 miles OCI
8 qts. 10,728 miles OCI

This is interesting because Mercedes recommends a 10K mile OCI for my car. Seems to be in agreement with this method's result. Coincidence?


Cheers,

 

[Dave Hess]

The bigger the oil sump, the less contamination

 

[blupupher]

quote:

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Originally posted by LT4 Vette:
The bigger the oil sump, the less contamination

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Well, same amount of contamination, just diluted more.