I have an 8 ton Welbilt splitter, uses a bottle jack. Don't use it too often in the winter, but I needed some splits split down to kindling last night, and it seemed to wheeze on some of the denser pieces. I wonder if it is because of the cold (it was about 30), or maybe needed a top off? I haven't noticed any oil on the wood or concrete, but I think once or twice there might have been a light residue when wiping it down, so I am not sure about oil loss (I've had it for two years). I have never had to replace any oil, but the manual has the following cryptic (to me) words after giving instructions: "Add hydraulic oil until the cylinder is approximately 3/4 full. (Oil weight is approximately 0.7/1.543lbs)" Does that mean the weight of the bottle when the correct amount of oil is added, or the weight of the oil itself? Or does it refer to something else? Sorry for such a dumb-a$$ question, but I am always a little timid when attempting something I have not done before with something that will cost me money if I goof it up. Also, is there a particular oil that would work in both warm and cold weather equally well?