My car is a GM / Holden / Vauxhall / Opel Astra (AH). The Holden owners manual says to use a 10W-30 or 15W-40 oil that is either A3/B3 or A3/B4, no mention of API. They say to change the oil every 15,000KM or 12 months.
Reading some UK & Vauxhall web sites, many people in Europe use oils like M1 0W-40, and Vauxhall give a OCI of 30,000KM and 24 mts. Wow !!
So the car is I-4 but everybody tends to run 40wt oils in them, so the GTL SHU 5W-40 is not out of place in this engine. Which BTW is a little ripper.
My previous few oil changes were with things like Valvoline DuraBlend 10W-40 semi-synthetic A3/B4 at 12 mts OCI. A great oil, and many other Astra owners run a 10W-40 semi-synthetic and change annually.
So running the DuraBlend 10W-40, the engine had a slight tick when cold (cold engine, but I live in a warm climate), but this tick went away as the engine warmed up. Changing to the GTL Shell Helix Ultra 5W-40, I noticed no tick on a cold start. The engine was quiet right from the beginning. The engine was also smooth and quiet when hot (fully warmed up - std operating temp). But, when half warmed up, after a few minutes of driving the engine tick returned, and stayed for quite a few minutes until the car was at full temp.
It most noticeable when you go to the local shops to grab a few items. The car half cools down, and when you start it up, tick-tick-tick-tick like a box of rocks, as you drive through the car park. Never got that with the 10W-40 DuraBlend.
I think it's a good oil, and I thought at first it stopped my cold engine tick, but it more just moved it slightly up the temp range. Not a problem, just an observation.
I think this is a very good quality oil, and I should be able to extend the OCI and do two years on it. But, I'll probably just change it at Christmas like I always do, it's easy enough. Nice to know I can go a little long with my OCI if I have to, and not worry, if life gets a little busy.