Should of went with fast intentions.

Surprised to see so many people with this problem... I got curious so I went and looked at the Z1 install manual, and I would be willing to bet the problem is right here:
Either these aren't getting tightened during install, or the rubber washers aren't sealing well. I'd probably try removing them and using the thread sealant mentioned earlier in this thread instead.

If it does turn out to be something like this, you could tell Z1 to update the kit/instructions to include sealant.

For those of you wondering if the thread sealant works. The permatex stuff that ChaseZ recommended to me worked great and now I dont have any oil seeping through the fittings. But I did buy new lines, fittings and a new gasket for the sandwich plate just to be safe. To be fair to Z1 I bought this oil cooler used so thats my fault. I called Z1 and they said they updated their lines because of this reason.

How much did that cost you since you didn't buy the cooler direct? I am buying used as well and am concerned I will run into this issue.

If I were to do it over again I would just buy it new. I got my oil cooler for 350 then spent about 160 on new lines/fittings. Im still coming in under what a 25 row would cost with setrab/thermostat but, I would have gladly paid the extra $60-70 to have an oil cooler that was just one and done. When you are buying these things new you have to consider that there are rubber gaskets everywhere so when you unscrew it the gasket no longer seals correctly, add into the high oil pressures these things see and its easy to see why its leaking. If you are going used I recommend you buy new gaskets for everything including the sandwich plate.

Definitely not the answer I was looking for. I'm getting the setrab/thermostat 25 row with sheathed lines and ~3K on it for about 100 off retail.

I guess my remaining question is how many of these issues come from those who installed themselves as opposed to letting a good shop take care of it or didn't tighten those fittings. Guess we'll find out.

Mine has been on the Z for 6 yrs now. Still tight.

I just checked mine about 2 weeks ago doing oil change. 20k mi since install and not a drop.

Wow, this thread still alive. Sorry that I abandoned the thread.
Solution was expensive.
1) I replaced ALL fittings with Aeroquip. That solved fitting leaks, but at $35 x 4 plus work to take all apart and put back together.
2) Mocal core burst. I called Z1 and they informed me that Mocal is not good for Z because of spike in oil pressure on 370 cars at start up. They no longer offering Mocal core with that kit.
3) I ordered Setrab 19 row core and sent back Mocal core to Z1 for warranty refund. Incremental cost(net of refund) was about $100
New installation costs....don't want to talk about it :(

All work was done by very high end shops catering to track day crowd-I am not familiar with fittings/fluid lines to tackle it myself.

At the end all is working and no leaks.

I appreciate help from Z1, but they really need to look into what brand/quality fittings are used on their hoses.
tip: you have to use "shorty" oil filter with this kit, unless you have very tiny and burn proof hands and a LOT of patience:)

This is my 2nd oil cooler from z1 and love the quality and customer service

Z1 fo life lol