This is what I found on the Janome website.
"I have a Janome 6600 and in the manual it says nothing about oiling the machine. Does anyone know if you are suppose to oil this machine or not? I've always oiled my other machines but don't know if I should this one or not. Thanks!"
"QuilterPj, The 6600 is a self oiling machine and we do not need to oil it in the same way we did our old mechanical machines. Having said that... it is ok to place a drop of oil on the wick after many hours of sewing. The wick is located beneath the bobbin holder. If you remove the needle plate and remove the bobbin holder you will see a white plastic ring with a steel ring within it. In the center of that is a small hole with what looks like a tuft of lint. DO NOT REMOVE IT because that is the wick. It should appear oily. If you are not sure then use the tip of the tiny brush supplied with your accessories to poke it LIGHTLY. If you see oil then there is not need to add any more but if it appears dry then a drop of oil is all it needs. I will inspect it each time I clean under the bobbin case but I do not nessescerily add oil it. I also recommend that you talk to your dealer. Not all are comfortable with customers fiddling with their machines. My dealer is all about empowerment so he has shown me a few maintenance tips. Oiling the wick is one thing he said was ok as long as you do not get carried away and add more than a drop or two of oil."