FYI, if you send it to Leica, turnaround will depend on where in the world you live.
I had one very stubborn, persistent spot that I could not remove with wet cleaning. I don't believe it was lubricant, rather, something else from the environment. Anyway, I happened to be in the NYC area and inquired with Leica NJ about same-day sensor cleaning. They did it, but also explained that when an M240 is sent to Leica, even for something simple like sensor cleaning, it is required to go through a specific inspection procedure and checklist that involves an expensive dedicated piece of hardware. My understanding is this includes checking sensor alignment, etc. Apparently not all Leica service facilities (at that time) have this hardware, which means forwarding the camera to a location that does... Obviously, this results in significant service delays.
I'm just mentioning this as a warning. If your local Leica service center isn't fully equipped, then for something simple like sensor cleaning, you're best to have it done by a competent service center/dealer/friend, etc. if you're unable or unwilling to do it yourself.
Having used the M9 for over three years before switching to the M240, which I've used now for nearly two years, I have not noticed any difference in quantity or type of sensor dirt/dust/oil. Every once in a while I will get what looks like a spot of something sticky, but typically this happens during the process of blowing out the sensor with a blower bulb. Difficult to know if it's from the camera itself, or something from the external environment that got stuck in in the lens mount area. Lately I blow out the lens mount and shutter area with the shutter closed before doing the actual sensor cleaning to remove as many loose particles as possible that could potentially blow onto the sensor while trying to clean it.
I find most of the time M240 sensor dust can be blown out. I remove most of the remaining persistent specks with a sensor pen. Very rarely do I resort to a wet cleaning.
Compared to other digital cameras I've used, the M9 & M240 seem to attract somewhat more dry dust, therefore requiring more frequent inspections and blower bulb cleanings. Oily/sticky spots are definitely in the minority.
Originally Posted by btgc
Are those same people who say "Lens cleaning? I grab bottom part of my T-shirt and wipe off all moving crud and leave what remains after three strokes" ?
If the t-shirt is of the breathable, moisture wicking synthetic variety, then it is very much the same as the microfiber material used for reusable lens cloths. The problem with a t-shirt is whether the section of material intended to clean the lens has made contact with the skin, or how well the laundry detergent was rinsed out during the last wash...