@harryberry15
For Cultus, use only recommended SGP-Suzuki Genuine Oil Premium(Silver Grey Packing) in API SG 10W-40
Do not use 5W-30(It will be too thin) and thus not suitable for your Engine.
As per my knowledge, your 5w-30 shell hx 5 is coming in SN grade which has less ZDDP which is not recommended for Hydraulic Lifter present in Engine of your Cultus. You should use SG(Maximum to SJ and that is only when SG or SH is not available to u) otherwise stick to API SG providing by Suzuki 3S dealers
Use only SGP oil with Guard Oil filter & Air Filter. If u could find QAIM oil filter & air filter, it will be plus for your car otherwise Guard will also be OK please but do not use any other brand.
If u could write your city, then pakwheelers can better guide u . If you are in Karachi then i can guide u 3S near our location.