Cessna 172S Frayed Aileron Cable During a routine inspection an aileron cable (p/n 0510105-364) was found shiny (worn) where it passes through the ceiling pulley cluster. When it was viewed through a strong magnifying glass, many broken strands could be seen. Part Total Time: 2311.0 hours Diamond DA42 Cracked Fuel Tank During a routine inspection a fuel stain was noted in the left auxiliary tank area. The tank was removed and inspected. There were cracks found at several of the weld points where an internal baffle is welded to the bottom panel of the tank. A new tank (p/n D6028141100) was installed. Part Total Time: 625.0 hours Diamond DA42 Chafed Rudder Cable During a routine inspection, a rudder cable (p/n CA13190) was found worn with broken strands where it exits the (guide) tube (p/n 157727) about two inches forward of the rudder bell crank. This is approximately on the rudder hinge line. Part Total Time: 1313.0 hours Continental IO-550-C Leaking Dipstick Housing During a routine oil change a puddle of oil was observed in the bottom of the cowling. No oil was spilled while filling the crankcase. Having seen this problem several times in the past, the mechanic immediately knew to look at the dipstick tube (p/n 6494061) in the chafed area. As in all the previous situations, the hole is located at the first inside bend below the filler opening. Fortunately, once the dipstick is in place, it tends to fill the chafed opening and very little oil can escape through the hole. Part Total Time: 1209.0 hours Sky-Tec C12ST3 Rev. D Starter Housing Separation The pilot reported starting difficulties. The problem was obvious upon inspection: The starter housing had partially separated between the adapter housing and the main starter housing. Exterior bolts securing the housings together were intact and tight. The starter was replaced. Part Total Time: 137.0 hours Slick 4373 Magneto Cracked Rotor Gears Prior to reassembly, the magneto rotor gears (p/n M3827) on both magnetos had numerous cracks in one of the gear teeth. Two new gears were ordered and numerous cracks were found in one of the new gears as well. All three gears had cracks in the same gear tooth. Part Total Time: 125.5 hours