Performed 100 hour inspection on ENGINE. Compression: #1 70/80, #2 70/80, #3 70/80, #4 68/80. Drained oil and serviced with 8qts. Phillips 66 100AW oil. Replaced oil filter CH48111-1, cut open old filter and inspected, no metal found. Cleaned re-gaped and tested spark plugs, replaced spark plug gaskets P/N 07-00778. Replaced element filter P/N BA-6108. Tightened and adjusted 4 oil return hoses. Checked MAG timing. Work performed in reference to Cessna 172M MM, and IPC. I certify that this ENGINE was inspected in reference with Cessna's 172M 100-hour inspection checklist and was determined to be in an airworthy condition.