The oil filler plug had a bad thread. I filled in the oil, being very careful not to over-tighten or over-tighten (a pet peeve of mine and why I never go to "quick-lubes"), but the threads were too loose/fine. The connector is not properly tightened. The plug fell out within 1 hour of use and spilled oil on the leg and floor. Reordered in the hope that this is an anomaly and not a normal manufacturing issue. If so I will come back for a refund. ***EDIT: *** A new hammer arrived and the oil filler plug was very tight. My guess is that the first one was removed during assembly because it was overtightened. After the plug was removed, it was snug and tight again. Very happy with the performance and incredible value compared to others on the market! 5 Stars. Otherwise it hits hard and is a great tool for the price. The only problem (other than the oil plug) is that you have to "hit" it to engage the hammer, making it difficult to accurately remove the shavings. Luckily I have a small jackhammer to finish the edges with.