A lot of the box store units have a problem associated with the return line and the tank, in as much as the return line is located too high or is simply dumped back in the axle tank from top either way it allows for a bit of air to get mixed into the oil. On some it is pumped in the side but the flow rate causes turbulence at the top of the oil level again possibly mixing some air with oil. In a worst case scenario an over filled tank will foam out the fill port. A small expansion /fill tank( 1-2 gallon) mounted higher the main tank in some fashion connected to the original fill port solves this. This gives you a completely full main tank as any expansion backs up into the aux tank and it also acts as a bit more area for cooling, eliminates any possibility of air mixing and adds an area for any air from any other source a place to dissipate. Other areas that are friction culprits- hard lines that are less than 1/2" internally, right angle fittings that are restricted to 3/8" or less internally, even straight fittings again restricted internally to 3/8". Haven't seen any box store units running 3/4" so the comments here are based on 1/2" materials. When I rebuilt my splitter I paid particular attention to the friction points and the oil tank system- my unit in original condition would give you a first or possibly a second degree burn if you came in contact with the cylinder. It now will run all day without any extreme heat issues.