About sludge and varnish

[hungdynasty]

I took off my 95 BMW 740's valve cover to change the gasket 2 months ago, I saw there was no sludge but some varnish(brown color) on the cam shaft area. Not really serious and I though it's clean enough( I've been using Mobil 1 or Castrol RS since I got my car in 1998). Last week I helped my friend to change the gasket for his 97 BMW 525, WOW! There is ABSOLUTELY no sludge and varnish, everything I saw was like new.(He's been using Mobil 1 too)My car's engine is still running very smooth, nothing wrong but I'm just wondering why we've been using almost the same oil(all synthetic) but my engine is not just as clean and nice as his. Any idea?

[ September 19, 2004, 09:35 AM: Message edited by: hungdynasty ]

 

[dickwells]

I am not familiar with Castrol RW but you have to watch Castrol oils very carefully to determine which is real synthetic and which is group III, this may be the difference between the two engines. The usage and oil change interval also may play in to this.

 

[hungdynasty]

Hi dickwells, Castrol RS is grade 0W40 or 10W60, very close to what you call German Castrol in North America, pretty sure it's a group 4+. I and my friend 's OCI is arround 10000km(6000miles), not much different.

 

[satterfi]

Maybe

The surface finish is different.

The previous owner used a different oil.

The cars operate at different temperatures.

The rings don't seal the same.

Different gasoline is used.

Pollution control equipment doesn't operate the same.

There are more free radicals in the blow-by on one car.

AMI professionally maintained your car.

 

[Ugly3]

Driving style, hiway vs city, PCV valve, and 50 other differences. No two engines are the same and a little "varnish" won't hurt anything anyway.

 

[Tim]

quote:

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Originally posted by satterfi:
Maybe


The previous owner used a different oil.

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Bingo!

Three years can do a lot....


Tim