I'm very curious about this too, as I'm facing a similar decision regarding replacing coupling caps on my phono. Thanks to Pepericoz for posting this question.
I've not tried Mundorf silver/oil, but I use silver/gold in phono stage & line stage components-- particularly in higher values where V-Caps become cost-prohibitive for me. The Silver/Gold are clean and neutral, and IME do not lack for bass as some have commented. Mundorf wrote to me that Silver/oil it tilted up in midrange and bass and that Silver/Gold is more faithful to the music "as recorded." Also, if the caps are to be used in a hot tube amp chassis, consider that the silver/gold are rated to a much higher temperature.
Whatever you decide, allow several hundred hours for the caps to relax and sound natural.
The OEM Jensen/BAT PIOs in my VK75SE are surpassed in all respects by V-Cap TFTF. I don't know if those Jensens are copper or alum. I have not compared Mundorf directly to Jensen PIO.
I think you'll find that PIOs in general have less clarity than teflon and other good film coupling caps. (Mundorf Silver/Gold are not oil caps.) If you want to experiment with a nice oil cap on the cheap, consider russian K40Y-9s on ebay. Knowledgeable posters at AA believe these to be the best of the PIOs. I have a bunch that I haven't yet installed. They appear to be built to a very high standard.
Indeed BAT oilers look identical to Jensen. My assertion as to their identity follows several posters and webzine reviewers who have stated that BAT PIOs are specials developed by Jensen.
Of the Mundorfs I have tried only Silver/Gold. They have handily surpassed REL RT and Hovland Musicap in my line & phono stages. But the most immediate & dramatic improvement was replacing BAT PIO with V-Cap TFTF. V-Cap TFTF was also a major improvement over REL teflon in my LS. In my system the phono passes signal through two Mundorf Silver/Gold and one V-Cap TFTF coupling caps. The CDP passes only through two V-Cap TFTF. These sources sound damned close, which I believe testifies to the quality of Mundorf.
Dgarretson, thanks for all your inputs,you have help me saving time on the path of trying different caps, i have installed jensen copper PIO on my cary superamp and so far not passing the break in time but it sounds pretty good comparing to the stock kimber caps, i have ordered some mundorf caps silver/gold for my cary rocket88 as coupling caps also for my audible illusion L1.i will let you guys know how they sound with cary rocket88 and AI L1,my next adventure will be V caps if my budget allows me.Have you changed out those electrolytic caps on your equipment power supply with better one? if so, is there any improvement? and which one is good and affordable eletrolytic caps available today. Many thanks and have a happy holiday
Tim, Jensen 4-pole caps are good, if expensive. Rubycon ZA and ZL work well in small filtering positions. Space-permitting it's effective and cheap to parallel Rubycons up to whatever capacitance is necessary. This can get large in battery supplies.
I put the Jensen/BAT PIOs into Cary 2A3SE monoblocks, where they improve upon the stock Audio1 coupling caps.