Need to define what 'fairly quickly' means, top the oil up to Max line and when it reaches the Min line find out how many miles you have driven in this period and report back.
5w30 will flow better than 10w40 when cold and 10w40 will be thicker when hot compared with 5w30 which might be advantageous if modified.
I tried 5w40 in my MK5 and it made a small difference to consumption possibly around 150mm difference over the same mileage as 5w30...so not a lot.
You should not use 10w ANYTHING because it will take longer (up to another 30 seconds when it's very very cold outside) for oil to fully circulate around the engine.
The best compromise would be 5w40 and this is what I used on my TDI and that had 110% more power than it left the factory with and was fine at 150k
Incase it's not known XwYY
x is the cold weight
YY is the hot weight
(lower weight = thinner/lighter oil). An oil which is too heavy/thick cannot circulate properly especially in turbocharged engines this is of concern.
I use Mobil1 in mine for the moment. I might try that Millers powermax oil or whatever it was called that Alex recommended. But it's twice as much as normal oil. That being said, it's cheaper than a new engine.
