Originally Posted By: shDK
But are there other reasons beside lowering fuelconsumption? Like the use of the car. Ones drove with with a collegue from the us who was moved over 2 month before. We drove from Denmark to ulm i southern germamy. And he was pretty amased and a few times a bit nervous on the trip simply because og the speed people where going. Especially down thrue germany. Can higher operating speeds be a reason ?
No it's the Green party in Germany who push real hard to reduce oil leaks and engine oil waste. The move from 5/30 to 5/40 for older cars was partly the result of leaky VW TDI's running out of oil after a good full power session on the autobahn, as that resulted in most lube shops erring on the heavy side in terms of what is listed in their oil guides.
At present the German auto sector are just sticking to using the best oils for the job, not for fuel economy, although they have moved slightly lower in terms of some auto box oils to reduce fuel consumption figures.
One point about modern engines, is that if you use an oil that is too thin, the engine won't fail like old ones did, a valve won't drop or a bearing won't fall apart, they just start burning and leaking oil. Even when the rings start to break up they still run, so most owners scrap them because of leaks, high oil consumption, smoke or emissions tests failures, assuming they don't just run out of oil first.