S4er

comment like "it is a good way to get new turbos" is not helpful : )

Vtec_Killer

much thicker than 0-30. It takes longer for it to heat up, thus will not get "into" your turbos fast enough(i.e. like in the morning when you first start it). Furthermore, since it is thicker, you have more chance to clog the oil line going into your turbo if you do not do a sufficient cool down.

Just wondering, why do you ask about such a dramatic change in oil(15-50)? Most others ask about 10-30 or 10-40. Why the choice in this oil?

NASA racer

there aren't all that many modern cars with oil passages large enough to smoothly flow 50 weight oil and there is NO lubrication advantages in a car that wasn't designed for it.

Nogaro

Most turbo cars actully use pretty thick oil for better protection, but seems its not so in our case

captainbilly

It's not bad for turbocharged cars in general, just the S4-2.7t. It seems that Audi has recognized a lubrication problem on the turbos on the 2.7t engine related to high viscosity oils. One the engine is hot you could probably use 15-50 or anything else but when the engine is cold the heavier weight oils don't flow as well due to the higher viscosity. The general idea of multi-weight oils (5-30, 5-50, 15-50, etc as opposed to 30, 40 ,50 etc.) is that they flow like the lower number when cold and the higher number when hot. With conventional (non-synthetic) oils the additive that gives the oil it's multi-weight characteristics breaks down over time and you end up with the lower number all the time. With the synthetics, that I have experience with, the multi-weight rating is inherent to the base oil and does not break down over time. The reason that some people are concerned about light weight conventional oil is that when it breaks down under hard use you are left with a very light weight oil that will not support the bearings under heavy load. By the way, the biggest problem with lubrication is at high load low RPM. Most bearings in cars are hydrodynamic, which means that the bearing rests on a film of oil that is caused by the rotational motion of the bearing surfaces (sort of like a water ski on top of water but not exactly).The faster the bearing turns the more force it takes to push through the oil film. High RPM is hard on the viscosity improvers, VIs in conventional oil because high rpm generates a lot of heat and heat is what breaks down the VIs. This is generally not an issue for synthetics.

DrHandball

In either case this is not good for vehicles with tight tolerances such as the S4 and A6 2.7T.

Synthetics have better flow characteristics at all temps as well as improved lubricity when compared to dino oil of the same spec.

DrHandball

Good response captainbilly. You an engineer??