At the last oil change for my '76 300d about a week back it turns the filters height was perfect but it's not as wide as it should be. So instead of a fairly tight fit in the cannister there is probably 1/4th inch space between the outer wall of the filter and the inner wall of the canister itself.

So is this a cause for concern? Will the filter still do it's job over a 3000 mile change interval or should I order the correct size (which I thought I did..) and reinstall it?

What is the manufacturer (the brand name of the maker) and part number of the filter that you installed?
Was the Old Filter fatter than the newest one?

On my later model 300D there is at least 1/4 inch space between the outer housing and the Filter Element. However your oil filter is not the same as mine.
I have used Filters made by Mann, Mahle and Bosch and the all have about the same 1/4 inch of space between the housing and the Filter.

If it is the correct filter for your car and made by a good quality company there is no reason it should not last for 3000 miles until the next Oil Change unless you are having some unusual problem with your Engine that would cause it to plug up earlier.

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84 300D, 82 Volvo 244Gl Diesel

It's made by Bosch, part # 72127. The oil I use is Mobil 1 5w40 diesel oil.

For argument's sake lets say theres a 1/2 - 3/4" space between the outer wall of the filter and inner wall of the cannister.. Will the oil filter still do it's job or should i find the right size and re-install it?

And btw, having the wrongs parts sent to me seems to happen far too often. Can you recommend a source that doesn't make these mistakes?

Your notion that the filter should fit tightly in the housing is a mistaken one. In fact, a tightly fitting filter element could not function properly.

Just for referance this place shows the same 72127 Bosch Filter for your vehicle. But, I would assume it is for Vehicles sold in the US. Euro 300Ds may or may not have the same Oil Filter.
http://www.**********.com/search/product.aspx?sid=nfma0w55apflri45i4r45fey&makeid=800016@Mercedes&modelid=1193666@300D&year=1976&cid=oil%20filter%20kit@oil%20filter%20kit&gid=5341@Oil%20Filter%20Kit

I also noticed when I checked a filter cross referance that the same filter is used on a lot of American Engines including industrial type equipment.

To address the size issue the only way to find out which of the filters filters best reguardless of the outside diameter of the filter would be to look at the newest ISO test specs for different companies filters for your year and model. The newer tests I believe also test how much the filter can trap.
I think it is the type of Filter Media that is used inside that makes a differance. A skinny Microfiber or Celulose filter may filter better than a Fat Filter filled with packed Cotton or Cotton Gin.
With any Filter how long it will last will depend on how clean your Oil is.

Another problematic area as far as I am concerned is that when I cross referanced the Bosch Filter to Wix; it said it the Wix version was a 30 nominal Micron filter (on the Oils 1st pass through the oil filter 50% of the 30 Micron or larger particles are filter out). To me this is poor filtration.

Unfortunately few filter companies supply the filtration info on their filters without asking them directly. This means there is no way to tell what level of filtration you are buying even from a well know Brand.

In General from reading the forum I have not read of any particular Brand of filter that plugs up sooner than another brand.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the help, much appreciated.

um, how about
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1976%40%401976&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6183%3AMBC|1502%3AED|10000131%40%40300D&keyword=oil+filter&subcatid=P:240348@@Oil+Filter+Kit&mode=PA

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