If you’re interested, I created a spreadsheet based off this guide which lays out the required materials in a grid and displays all the ore required for leveling up engineering. Let me know if you’d like to have it.

Orange – this is not guaranteed. This is a small chance that crafting an item will not gain you a level. I suspect the success rate is something like 99 out of every 100 attempts, so it is very rare not to gain a level
Yellow – in my experience this will usually give a level in about 7 out of every 10 attempts.
Green – in my experience this will usually give a level in about 3 out of every 10 attempts.
Gray – this will never increase a level.

I’ve noticed one thing with all your guides. I think this is wrong:

Orange – High chance of increasing Engineering level when crafting this item
Yellow – Moderate chance of increasing Engineering level when crafting this item
Green – Low chance of increasing Engineering level when crafting this item
Gray – No chance of increasing Engineering level when crafting this item

Orange is guaranteed to level.
Yellow is High chance
Green and Grey are fine.

I would say Yellow is High chance because it levels more than it doesn’t.

Cheers.