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Did some catch can testing - JLT and RX cans - results here


Papa Smurf
I had an opportunity to run some testing in a track environment with two catch cans over the past couple months. I had purchased a JLT can right after I got the car as it was quite common. It caught some oil as I drove, so I figured it was doing a reasonable job. Through a forum member over on MustangSource, I got connected up with the guys who sell RX brand oil separators. I'd never heard of them, but they offered me a can to run some testing - figured why not.

Summary of my findings are below. I realize it's limited data points, but the results are pretty clear, especially in the couple days of testing with the RX first in series with the JLT.

I ran either the JLT first in series with RX or visa versa.

I ran 5 track days with a bit of street driving intermixed.
3 days at Thompson Speedway Motorsports Park
- 1 day with JLT in line first
- 2 days with RX in line first

2 days at Watkins Glen
- Both days with JLT in line first

Thompson seems to result in MUCH more oil coming through the separator, as shown in the results. It's a lot of hard on the gas, hard on the brake with minimal shifting and basically the whole track is done in 3rd gear.

Watkins Glen is a much faster track overall with more time at WOT, mainly in 4th gear

With the exception of the first outing at Thompson with the JLT first in line, it essentially caught no oil whereas the JLT caught just about everything with only trace amounts getting past the can

And below are the numbers from my testing. I'll clearly be keeping only the RX going forward, as the JLT catches almost no oil. I realize it seems to be well known that the JLT is not very effective, but having data to support this is good proof.

Lastly, I was amazed at how much oil was caught in only 2 days at Thompson (plus about 200 street miles with almost no revs over 3500) this past week over 2 outings. About 124 mL is what I measured coming out of the RX can. That's over 4 ounces...

Good work. This is not a comment on either of these cans but if you're on the track a lot go straight to an oil breather like in the thread below.


Papa Smurf
Good work. This is not a comment on either of these cans but if you're on the track a lot go straight to an oil breather like in the thread below.

Yeah, I have started considering this too. Might end up going that route next season. Largely dependent on if I get out more than this year, but appreciate the input!!

302 Hi Pro

Boss 302 - Racing Legend to Modern Muscle Car
So happy I went with the Peterson set up. After I installed the JLI, I thought it worked, then after running the JLT for a few thousand miles, I pulled the TB. Found light, ever so light trace oil. Knew then the JLT was helpful, but had to get something better.

Engine oil stays much cleaner now. After 3k miles it's still clear and light golden honey color. Before the Peterson set up, the oil would be black in 1,500 miles or so.

From the data, the RX looks to be doing a good job. If your on the JLT or closed PVC system, the engine will really suck oil as you come off throttle and during idle periods when max vacuum conditions exist. The left side, (passenger side), hose connection is on the vacuum side of the TB.

This is also why no oil is seen in a catch can installed on the R/side.

Have fun with your Boss and if she is a keeper, then install one of these systems to limit, or eliminate carbon deposit build up on your intake valve faces and pistons.



tree hugger
On my last car I had a TVS blower and a JLT catch can. It did a mediocre job. Instead of swapping to a different brand I caught a deal on another used JLT can and ran two in series. This worked much better as the second can caught almost as much oil as the first can. I had very little oil residue in the intake after this mod.


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