The twins need some grease to open up the pipes.
Oil is used for in all kinds of places.
Like restaurants.
Visit the Ramen shop and do some pixel hunting: ?
There is some grease dripping from the table.
Collect it. You need a container. A cup or similar.
There is an old mug in the Dark Alley. On the ground next to the Rocket Soda machine. Collect the grease into it.