How to draw a cross section of an engine in TikZ

Question

I would like to convert the following picture, which is a cross section of an engine, into a TikZ code:

• How to start with this picture?
• How to draw the walls and pipes in an easy way?
• How to draw the oil (the hatched area)?

Answer 1

How to draw the oil (the hatched area)?

One way may be to use pattern=north east lines from patterns library described at page 730 of the PGF Manual:

\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{patterns}

\begin{document}

\begin{tikzpicture}
\fill [pattern=north east lines] (0,6) -- (0,0) -- (10,0) -- (10,6);
\draw  (0,10) -- (0,0) -- (10,0) -- (10,10);
\end{tikzpicture}

\end{document}