Re: synthetics

[John Graham <jgraham1@erols.com>]

Sargent Schutt wrote:
> 
> John Graham wrote:
> 
> > > It would be interesting to compare your engine oil consumption over the
> > > next few months with your pre-synth days. I made exactly the same
> > > changes as you on my 91 200q about 5k miles after I bought it, and noted
> > > that with the change to synth my car started burning oil (1/2 qt per 4k
> > > miles). Since then I've switched to dyno engine oil (20/50) and have
> > > noticed less oil consumption. This all due to the detergent effects of
> > > the synth engine oil.
> > But were you useing a 20W50 synthetic?
> 
> Yes.
> 
> > >
> > > In the tranny, I originally put in Mobil 1
> > Bad move. Mobil 1 is a GL-5, even Mobil says don't use it in a
> > Quattro.
> 
> Hmm, the Audi tech said the mobil-1 tranny oil he put in was the appropriate
> weight. Sure was dirty when I changed it 20k miles later, though (to the
> Redline).
Mobil-1 gear oil is GL-5 and is corrosive in a Quattro tranny.
Redline MT-90 is a GL-4 and is ok.
> 
> > > ( at143k miles, made an
> > > improvement), then recently changed to Redline - BIG improvement in
> > > shifting with the Redline. I highly recommend it.
> > >
> > > Anyway, keep me posted (the list) as to the change in oil consumption
> > > levels (if any) you see in the coming month or so.
> > >
> > Make sure it's the same grade oil like 20W50 dyno to 20W50 synthetic.
> 
> Why should it matter as long as the weight is appropriate to the outdoor
> temperature? That would seem to be the important thing. Regardless, the
> detergents in the synth clean out the buildup that has become part of the
> motor (after high, 100k + miles), particularly after 140+k miles when I
> switched. (currently 167k miles), That's is what I'm after here. More proof
> of that phenomenom - I have heard about it, I experienced it; How many more
> out there?
> 
Because synthetic oils don't act the same as reg. oil under pressure.
A 5W30 synthetic may look like a 5W40 reg. to hot runing engine.
You don't need more proof of the phenomenom because it's true.
But it's the why. Just how much gunk doe's one let build up in the engine?
I my old days before synthetics, I use an engine flush every other oil change.
Because you don't want oil pump by pass valve to get stuck.:-(  

John
1990 CQ