skimants

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Bob W.

To me it sounds like they don't want you to use, say, 2 quarts of amsoil with 2 quarts of regular oil. After draining the oil and changing the filter, I don't think there would be much left to mix with the amsoil...just a bit of residue. BTW, it also says not to use amsoil with 'after-market products'. Engine flush an after-market product, isn't it?

Paul H. (in MD)

To me, as with virtually anything else, choosing the right oil was a trade-off. Since I have a turbo and drive it hard, I decided on synthetic, specifically because of it's ability to better handle the heat generated by the turbo. There are probably other benefits to using synthetic, but this was the only one that mattered to me. FWIW, I ran my last car (a '92 Saturn SL2) HARD (redline constantly) for 150,000 miles on conventional oil (changing it religiously every 3000 miles) and it was as healty at 150,000 miles as it was at 75,000, even with a +25HP "upgrade". Until I over-revved it going around a corner one day and spun a bearing (stupidity + oil starvation due to gravity and inertia). Oops. But I digress...<p>There are many good synthetic oils on the market. The two of them which are most available to me (for a reasonable price - except for AMSOIL which I have no idea where to get) were Mobil 1, and Castrol Syntec (Full Synthetic). So my decision was basically between these two. If I can find a good (i.e. AFFORDABLE) source for Redline or AMSOIL, I would consider these also.<p>Unfortunately I had two opposing goals: <p>A) Use thicker oil to protect the engine, because it gets hot sometimes here in the summer, and because I drive the car hard...VERY hard. <p>B) Use thinner oil for less parasitic drag(!!), better turbo spool-up, and better flow on initial startup. <p>As you can see, not an easy decision. In the end, it came down to kinematic viscosity @ 100C. This is where it mattered most to me. At this temperature, here is how they stack up (higher numbers are thicker):<p>(Kinematic Viscosity, cSt @100C; data gathered from the manufacturers' respective web sites):<p>Castrol Syntec 10W30 = 11.5<br>Mobil 1 10W-30 = 10.0<p>Castrol Syntec 5W-50 = 19.5<br>Mobil 1 15W50 = 18.0<p>As you can see, at the higher temperatures Castrol Syntec is slightly thicker at 100C than Mobil 1 in the 10W-30 grade. There has been some concern experssed here that that 10W-30 is still a bit thin if you drive your car especially hard (ME!!); but the next level, x5W-50, is said to be too thick. So if I HAVE to go x5W-50, I would go with Mobil 1 because it is the thinner of the two at a viscosity level that is already more than high enough. Since I don't think I HAVE to use x5W-50, I decided to go with the Castrol, because it is the thicker of the two at a viscosity level which may still not be thick enough (unfortunately only time will tell). I hope this makes sense to everyone.<p>The fact that my Audi dealer also uses Castrol 10W30 exclusively (they carry both conventional and synthetic) may have given me a little extra piece of mind (though not much since dealers all vary and it is usually a case of which oil manufacturer gave them the best deal).<p>So, no brand loyalty here (sorry Julia, even though I went with your oil anyway!). Strictly by the numbers. <p>I hope this helped, and I hope all my little editorial comments in the parentheses don't annoy too many of you English majors... ) (If so, sorry but you will just have to deal with it!)<p>Paul<br>'98.5 A4 1.8TQTipS in Pearl (Castrol Syntec Full Synthetic 10W-30)

Paul H. (in MD)

...but wouldn't the residue from the engine flush be worse than the residue from the conventional oil..?

Bob W.

Thanks Paul, very interesting...nt

Type SH

The engine flush is pretty thin, it really doubt anything would be left behind. But again, I'm not an expert hehe ... I'm just guessing that because the engine flush is really thin, it should bring out everything that's in the engine, which would let you safely pour in the syn. oil.<p>As for mixing conventional and synthetic oil, I still think mixing the two isn't a good thing. I mean, the conventional oil is just normal oil from the ground and synthetic oil is made of special chemicals with different formula. I wouldn't doubt mixing conventional oil and synthetic oil is better than mixing two different brand of synthetic ... however, I would avoid seriously avoid mixing conv. and syn. myself.<p>Finally, engine flush ... Amsoil has their own engine flush. So, it must be 100% compatible with their own engine oil. Besides, I don't think there will be residues left behind. I have seen people using Amsoil engine flush and switching to Redline, Castrol, Mobil, etc. oil, and everything runs fine.<p>~Prelude SH

DwayneC

I think they mean 'Junk 50' and the like.<p>Dwayne<br>94 S4

JETPILOT

The oil to get is ow/30. Amsoil series 2000 preferably, or Mobil 1 has one now. They will NOT void your warranty and that weight is FULLY compatable with the audi engine. I have been using it for the last 30,000 miles. <p>I live in South Florida and the oil temp never once rose above 190. Amsoil 0w/30 can go "to 20,000 mile drain intervals, and still be within specs for contaminants. Contrary to popular belief when oil gets brown it is NOT time to change it. <p>Synthetic oils are FULLY compatible for use with conventional oils. There is also no need for an engine flush. All your doing is pouring kerosene into your oil and destroying it's ability to film and protect during the 20 minutes your running your engine. And after it's drained flush will still be in your engine waiting to contaminate the new oil.<p>Viscosity plays little part in determining the protectivness of synthetic oils. Hence 0/W30. <p>Lets try to put the past behind and move with technology.<p>Definetly check out the Amsoil site. Get a case and some filters. Will cost about 100 dollars for 3 changes. But don't changer it for about 10,000 miles. They have great filters also.<p>My $.02

state

A trusted source (local OEM Engineer) told me that Amsoil is nothing more than re-pacakged Mobil-1 (first-hand account). Mobil-1 also scored the highest in a number of bearing and real world tests conducted by this automobile manufacturer. I have used Mobil-1 for many years (4 vehicles), and will continue to do so. Having removed the valve cover on a number of occasions, I saw the components were notably cleaner (devoid of varnish) and seemingly un-worn compared to engines that use dino oil.<p>Viscosity does matter. SOTP definitely has the turbo spooling faster with lower viscosity oils. Unless you live in a very hot climate AND consistently have big engine loads, I'd stick with a lower viscosity oil (I.E. Mobil-1 Synth 10w30). 0w30 is probably OK for many applications, but I won't be using it. The reason for offering such a spectrum of oils is directly tied to application. <p>These threads never seem to die (in every auto list I've ever joined) and pop-up all of the time. This should be an FAQ item along with fuel octane rating, MTBE re-formulated fuel/oxygenatd fuels, etc.<p>Regards,<br>Searl

ChrisWB

You live in South Fla, have a 1.8T w/chip, and your oil hasn't ever rose above 190F? Are you sure you've got the readings correct? I'm using Mobil 1 15W-50 it's regularly about 225 running temp, up to 240 at V_NE.