Porsche 968 CS Black Exhaust sheen on rear bumper?

[wasserkuhl]

Greetings from Australia.

I have a 1993 968 CS. The motor is a Porsche exchange replacement with only about 3k miles on it.

Anyway, I recently changed from a Castrol 15W 40 Blend mineral oil to a Brad Penn 20W 50 green oil (ZDDP in it, recommended etc...)

Anyway, there seems to be a mild black sheen on my rear bumper now, just above the exhaust tip, which I have noticed since using Brad Penn.

Could this be related to the Brad Penn oil and a side effect from the ZDDP through the Catylitic converter? or a faulty O2 sensor caused by this type of oil?

Or completely un-related?

I am going to drain the oil and have it analysed next week and re fill with Castrol synthetic 10W 60 (Hot summers here)

I have always used castrol products but could see the benefit of ZDDP oils as well for Porsches of this vintage.... however Brad Penn have advised to me that its the wrong oil and I should be using a modern synthetic or a mineral like I had in previously with more frequent changes(car gets driven hard)

Any commentary would be much appreciated:

[Rasta Monsta]

Brand new 968 motor in Oz? Holy cripes, what did that cost you?

[wasserkuhl]

Originally Posted by Rasta Monsta

Brand new 968 motor in Oz? Holy cripes, what did that cost you?

Just under AUD 10k exchange, so about 10k USD atm.

Cheaper than a rebuild down here. Makes very good screaming power as well.

Anyway, any commentary about the oil?

[VII]

Originally Posted by wasserkuhl

so about 10k USD atm.

wow. $10k for just the engine? A stock engine?

[wasserkuhl]

Originally Posted by VII

wow. $10k for just the engine? A stock engine?

Yep, about 9.5k exchange long motor.

Not too many specialists down here who can rebuild one of these for much change out of 8 grand so a brand new motor from zuffenhausen made sense to me.

on topic. any comments about the bumper sheen?

[962porsche]

a motor with only 3k and you want to use a synthetic ? i would not ! the black crap on your bumper is it running to rich of oil ?

[Rasta Monsta]

Well, is it an oily sheen, or more black carbony dust, like unburned fuel?

[ernie9944]

Originally Posted by wasserkuhl

Greetings from Australia.


I am going to drain the oil and have it analysed next week and re fill with Castrol synthetic 10W 60 (Hot summers here:

Any commentary would be much appreciated:

My car 93-968 81,ooo klms or a little bit over 50,ooo miles oil in it since new Castrol GTX 20w50 conventional ,ex 83-944 same oil 110,ooo miles no black sheen on either bumper .Why don't you try that oil for a while & see.

[wasserkuhl]

thanks guys for the comments, the sheen is actually unburnt fuel *slaps forehead, I have a chip in it and intake / exhaust improvements. After careful analysis with an expert we worked out its fuel.....

I have changed the oil to castrol 10w 60 anyway as I have gotten some very good results with it.

i would like to get some of the Castrol GTX 20w 50, however we don't have it down here :-(. only 15w 40.

Anyway, keep wassergekuhling guys and thanks!