OK.
Now as you're feeding Havoline 20/50 SG Grade, which is pretty much thicker oil. So if will go again to use 10/40, it may not bring good results as once can expect.
So, I'll suggest to stick with 20/50, but there is seriously need to change the oil company
Never use ZIC hiflow, its 20/50 because it is of API SM grade.
I've recommended to lot of people here to use PTT Performa 20/50. This is API SN grade. And most importantly, it’s the best oil in 20/50 nearly 2 times better than havoline (as per my personal experience).
Try to find this oil (PTT Performa 20/50) and feel the difference. Can keep the changing interval as 4K.
Frankly, Suzuki cars are not good to use the synthetic or semi synthetic oils. Their new cars need 10/40 oils and after a short time 20/50 for rest of engine's life. So just put aside your working to feed the oil to the car according to API's rating or grade recommended in manual or Engine's requirement. And just try 20/50 Performa oil. I can assure your experience will be far better than Havoline.