Kneale Brownson

from 7.1 to 11S and, again, told dealers that 11S was backward compatible with 7.1. Audi did not say to substitute 7.1 for 11S with the newer pumps, racks and boosters, but did say dealers could safely put 11S into 7.1 systems. Audi started supplying dealers with 11S when they ordered G002000 and expected it to replace 7.1 on the dealer's shelves. Audi didn't care about aftermarket suppliers of hydraulic oil still having 7.1 around. After all, if you bought oil from aftermarket sources instead of from an Audi dealer, that was your problem, not Audi's.

shortyq

I equate this to a debate on Castrol GTX 10w30 vs Mobil 1 10w30, with the same issues. If you don't consider a PS flush part and partial to hydraulic system preventive maintenance, the 11S will stay off viscosity and thermal breakdown longer. You can fill, backdate fill, mix and partially fill any G002000 system with either non-synthetic 7.1 or synthetic 11S as both meet the G002000 specification oil listed, and should be considered 100% compatable/interchangeable.

My rule of thumb is that a leaky system should use the cheaper 7.1 until the system is fixed. Once fixed, the 11S has a better heat range than the 7.1. All that said, flush the system every 2 years, 7.1 works just fine.

This misunderstanding has been around since the TSB in 1990. I get more road panic calls on this than any other on old school audis. P7.1 AND/OR P11S meet all requirements to the G002000 specification oil tag on the PS fluid resevoir. Any other claim to the contrary I consider to muddle a very clear interchange of the specification.

My .02

Scott J

anolin

hehe wow I thought I was asking such a simple question :-)

shortyq

The difference between the two fluids is only in the heat spec. The 7.1 is high temp rated at 100C, the 7.11 is rated at 140C. The cold spec of the two fluids is identical.

Again, this indicates that if you have a turbo car, or spend a lot of time in stop and go traffic, or in hotter climes, the 11S is going to resist 'viscosity and thermal breakdown' better than the 7.1. For a non turbo car, one that's on the highway all the time, or driven in the colder climes, the 7.1 should prove more than sufficient.

IME, I really don't see any difference between the two in terms of 'longevity'. Heat cycles of the car, eventually takes it's toll on either. A 2year interval of system flush does extend the life of both equally IMO/E.

More .02

Scott J