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Shell Helix has about a dozen different variants - those two words define nothing. I'll disagree with Skidpan that there's little difference between 5W-30 and 5W-40 - it's enough to ruin a good engine!
To try to answer the OP - the car maker will have designed/developed the engine to run on a particular viscosity of oil, varying little around the world despite big variances in climate as the internal running temperature isn't affected much by ambient heat, that just generates more waste heat.
So if the car maker says xxx-30 then use a xxx-30 oil - the first number is the cold viscosity and better protection is given the lower the number, as the thinner oil will protect the engine quicker during start-up which is where most wear occurs - so if a maker specifies 5W-30 then 0W-30 can be used and IMO is better - but 10W-30 shouldn't be used and neither should 5W-40.
The oil recommendation should include an ACEA grade - that's even more important than viscosity as it affects things like catalysts and DPFs.
Recently, my cars have needed 5W-30 ACEA-C3 so I've used 0W-30 ACEA-C3.
In the case of VW Group cars, there's an additional layer of specification, eg VW 507.00 or whatever - but oil containers will have that marked on the back IF approved, along with other brands approvals - websites like Opie oil allow you to search by manufacturer approval code.
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