Option to not have tar as by product on recipes where it does make sense.
From my perspective tar as a by product only makes sense when dealing with the crude oil,
So tar as by product seems very weird from the following recipes (already pure oil products are used as input):
- Heavy oil cracking
- Light oil cracking
- Solid fuel from light/heavy oil
- Lubricant
- rocket-fuel
- super conductor
- electrolyte

My personal "canon" is that heavy and light oil still have some amount of impurity in them, which is why they're byproducts from heavy/light oil. I don't think I'm going to add this as a setting, to avoid contributing further to settings page bloat... That said, this is an easy change to make in a tweaks mod:
ScrapIndustry.items["heavy-oil"] = nil ScrapIndustry.items["light-oil"] = nil
Tar is only directly added to oil processing recipes, . You can alternatively selectively disable recipes with ScrapIndustry.recipes["lubricant"] = {ignore=true}