The aversion would be that the OP claims he switched to the oil and was immediately noticing new noises and issues. He has since recanted that statement and now claims all is good.

All that aside, I haven't looked into "experimenting" with alternative viscosity oils not covered/specified by the warranty until this thread. There is a good amount of support for the Mobil Euro 0W40 and plenty of approvals. Due to the OP's flip flop opinion on the oil, I have taken it with a grain of salt and decided to try it myself.

There is definitely a noticeable reduction in engine noise and it even seems the exhaust noise has become quieter. Throttle blips aren't as pronounced. The car seems to have a little bit of a "smoother" feel and the engine seems more refined. We'll have to see how this affects MPG's due to being slightly thicker. I don't really care, but I am just curious.

The previous oil I had in the car was Mobil 1 Advanced Fuel Mileage Synthetic 0W30 (bottle specifically calls it out as maintaining warranty coverage for 5W30).

It's only been a few days with the oil but so far, so good. Nothing similar to what was originally reported by the OP.

 

Is there little to no concern about all the extra viscosity modifiers needed on a 0w40 oil?
Maybe that's why mobil1 starts with a better base oil...because they have to pump it full of non-oil modifiers to get it to behave like a 0w40.

 

My engine is built by GTM so I'm a bit different than an OEM G37.
When I had Specialty Z tuning the car he recommended 0W40 Mobil 1 European Car Formula for my engine.
The car has 23K total miles (13k since the build). I hear a bit of engine noise (slight chatter/lifter noise), but never loud or concerning. I haven't tried any other types as I trust my tuner and haven't run into issues.

 

Same here, GTM twin turbo kit, I change the oil myself every 3k with 0w40 European formula Mobil 1. Had same oil in my old G35 coupe for 100k m iles with no prob. Sometimes I also use German Castrol but it's very hard to find.

 

Does anyone uses royal purple? Is this just over hyped brand?

yay or nay?

 

Here's an independent test showing how RP stacks up.

AMSOIL vs Royal Purple

There's a lot of emotion that people put in their choice of oil. RP isn't a bad oil. Best thing to do is research it and go to bobistheoilguy.com and research used oil analyses for the VQ37. Go with where the facts lead you and select what you like, as long as you run something compatible with manufacturer's spec.