"Ugly oil" tells me that there is a combustion issue. If you change oil and filter regularly with quality product and you have really dirty oil between changes either there are contaminants entering through the intake or being created due to a misfiring ingnition. That could be anything from a faulty sensor or engine management computer to bad coils or plugs. That also causes carbon buildup on exhaust valves and loss of compression and wasn't that the issue to begin with? Hmmmmmm...we may be getting somewhere Watson!