fatbastard Posted December 31, 2006 Share Posted December 31, 2006 OK...I know I brought this up once before but tomorrow I have to change the oil in the wife's A4 and the size of the filter is freaking huge. They increased the size of the filter due to sludge problems. Now I am not an automotive engineer but it just seems like an engine with 40% displacement should have a similarly sized filter. As you can see in the pic, the filter for the 1.8 liter A4 is the size of a coffee can and the filter for the 2.5 liter Subaru is maybe 1/5th the size. Does this really make sense to anyone? I know part of the problem with the A4 was their oil change interval of 10k miles on regular dino oil but I still can't see why the filters would be so different in size. Any thoughts? Link to comment Share on other sites More sharing options...
whitetiger Posted December 31, 2006 Share Posted December 31, 2006 Ask your self this question-Which car had a large recall for an oil sludge problem? The subaru, or the audi? That big filter means nothing. Link to comment Share on other sites More sharing options...
fatbastard Posted January 1, 2007 Author Share Posted January 1, 2007 Well I am not sure there was an actual recall but that doesn't really matter....What is different in the Audi design that makes it more prone to sludge to begin with? I know they changed the filter to hopefully catch the extra crap in the oil and not by-pass the filter but I thought they also made the change for extra cooling capacity. When I look at the Subaru design, the filter is incredibly small and right next to the exhaust so the oil will be picking up a lot of heat and potentially breaking down the oil. Link to comment Share on other sites More sharing options...
mickeyd2005 Posted January 1, 2007 Share Posted January 1, 2007 It's surface area that counts and not the external size. The OEM oil filter from Toyo Roki (sp?) is the best in that regards. There have been cut ups done on nabisco. If you're really interested, the OEM Honda Odyssey oil filter will fit and is twice as large externally. I have seen Acura oil filters cut up and they were primo quality. BTW, I think Audi's solution is a lame bandaid for a poor design. Sludge build up is usually caused by poor oil gallery design. Link to comment Share on other sites More sharing options...
fatbastard Posted January 1, 2007 Author Share Posted January 1, 2007 BTW, I think Audi's solution is a lame bandaid for a poor design. Sludge build up is usually caused by poor oil gallery design. What is "oil gallery"? I understand that the Subie seems to be much easier on oil and the small filter is enough but I would like to understand how certain designs or lack there of can cause the sludge problem. Is it even possible to tell before you buy if they did their homework? When I have done searches on this I was surprised to see several Toyotas have been affected too. Typically I would have thought they along with Honda would be pretty good. Link to comment Share on other sites More sharing options...
mickeyd2005 Posted January 1, 2007 Share Posted January 1, 2007 Oil sludge can be caused by many things. The obvious is poor maintenance, but some cars are more prone to it than others. These cars suffer from a design flaw. And there are many possible problems. The fact that Audi used a larger filter with presumably more surface area tells me that they are trying to reduce the oil pressure drop across the filter. I don't think it increases oil volume or oil coiling that much. Oil flows through the engine and heads through small passageways drilled into the blocks. Due to distance from the pump and/or some sharp bends or dips, it may be possible that oil is flowing too slowly in some passageways. Just my opinion. http://en.wikipedia.org/wiki/Oil_sludge Link to comment Share on other sites More sharing options...
fatbastard Posted January 1, 2007 Author Share Posted January 1, 2007 Gotcha...so by dropping the filter pressure drop they increase overall flow which will hopefully keep the oil moving fast enough in certain passages to keep it from breaking down. By the way I did see the wikipedia and several other sites but from everything I have read it seems no one really knows how the sludge forms. One article even stated that while they believe some are caused by acids breaking down the oil causing these byproducts, that they haven't been able to recreate it in the lab. Link to comment Share on other sites More sharing options...
WhatV8 Posted January 8, 2007 Share Posted January 8, 2007 I have a 'fair' understanding of filter design and the like, but still would prefer a larger filter to help increase filtering capacity and keep my pressure drop low even with my short 3K mile change interval. I will look into the Odessey filter, seems interesting. On my SVO Mustang (2.3L 4-cyl turbo) I added a factory 90 degree adapter and a full size FL-1A filter from the stubby FL-300 model to help ease my nerves. So far no issues at 99K miles with my output bumped up to ~280hp. Saab's are also well known for sludge problems. When I was looking into purchasing one, I found a whole host of information on the issue. Most of it appeared to be related to combining a 10K mile change interval with a turbocharged application with a less than optimal oil pump pickup design. Sludge would build up under the oil pan pickup until the 'pile' reached the pickup screen and clogged it, which would starve the engines for oil and burn them up. That is if one of the chunks of sludge dislodge and make its way to the oil pump and pop it. Even folks who ran synthetic from new seem to be susceptible to sludge. Link to comment Share on other sites More sharing options...
FPerron Posted January 8, 2007 Share Posted January 8, 2007 My concern with the Subaru filter is its proximity to the header. Consequently, I've fabricated a "filter condom" out of heat reflective fabric. It's held on by hose clamps so it can be reused when I change filters. Link to comment Share on other sites More sharing options...
GTTuner Posted January 8, 2007 Share Posted January 8, 2007 My motorcycle uses the EXACT filter! Change it regularly and you'll be fine. Link to comment Share on other sites More sharing options...
Fallschirmjaeger Posted January 17, 2007 Share Posted January 17, 2007 I let my dealer do all my oil changes. I looked down there and couldn't find the engine oil filter, only the filter for the power steering fluid. (Well, I Think that's what it was, it was the only thing the right size.) Link to comment Share on other sites More sharing options...
bugblatterbeast Posted January 18, 2007 Share Posted January 18, 2007 OK...I know I brought this up once before but tomorrow I have to change the oil in the wife's A4 and the size of the filter is freaking huge. They increased the size of the filter due to sludge problems. Now I am not an automotive engineer but it just seems like an engine with 40% displacement should have a similarly sized filter. As you can see in the pic, the filter for the 1.8 liter A4 is the size of a coffee can and the filter for the 2.5 liter Subaru is maybe 1/5th the size. Does this really make sense to anyone? I know part of the problem with the A4 was their oil change interval of 10k miles on regular dino oil but I still can't see why the filters would be so different in size. Any thoughts? Ever look at an A4's turbo after even a little spirited driving? The two that I drove (some years ago) had red hot turbine housings and manifolds after what I considered spirited but not abusive driving. They didn't stop glowing after nearly 5 mins of idle with the hood open. Upon closer examination I couldn't find any coolant lines to the turbo. The VW engineers might be compensating for a lack of CHRA cooling. Link to comment Share on other sites More sharing options...
bugblatterbeast Posted January 18, 2007 Share Posted January 18, 2007 My concern with the Subaru filter is its proximity to the header. Consequently, I've fabricated a "filter condom" out of heat reflective fabric. It's held on by hose clamps so it can be reused when I change filters. I've been using thin aluminium ducting tape. I was too lazy break out the tin snips. Link to comment Share on other sites More sharing options...
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