Looking for input from anyone who’s installed the Stillen 19-row thermostatic oil cooler (P/N 400637) on a VQ37, specifically around post-install oil fill quantity. Running through what happened and want to sanity-check my understanding before the shop pulls the undertray tomorrow.
Car & Setup
2012 G37S Coupe, 7AT, ~95K km. Stock otherwise (running 5W-40 synthetic instead of 5W-30 — summer in Israel, this is standard practice here).
Just had three coolers installed at the same shop visit:
• Stillen 400637 oil cooler kit (19-row Setrab, thermostatic sandwich plate, Goodridge SS lines)
• Transmission cooler
• Power steering cooler
The shop isn’t Infiniti-specialized but does general performance work. I sourced all parts from Z1 Motorsports.
Install Note on Filter
Worth mentioning because it’s relevant: the shop initially wanted to install the OEM 15208-65F0E filter on the thermostatic plate. I pushed back citing Stillen’s explicit documentation that states the plate requires a PH3950-equivalent (larger sealing diameter to properly seal against the plate’s mating surface). They ended up using the filter that came packaged with the kit. So the correct filter is installed.
The Test Drive
~30 minutes, ~28 km mixed driving. Peaks of 150 km/h, RPM up to ~6500, calculated load peaking at 90%+. I was logging with OBDLink MX+ the whole time.
Everything on the logs looked healthy:
• Coolant temp: flat ~88-90°C throughout
• Oil temp: normal climb from 35°C to 91°C, then rock-steady at 91°C for the rest of the drive (cooler clearly working well)
• IAT: normal, ~30°C rising to 60°C as expected with heat soak
• Lambda: stable around 1.0, no lean events
• No DTCs, no warnings
I did NOT log oil pressure. The app I was using didn’t expose it as a PID. This is the one piece of data I wish I had.
The Event
Stopped at a red light after ~30 min. Heard a pop, white smoke came up from under the car. Shut it off immediately, pushed it to a nearby parking spot. Large puddle of oil under the engine bay, still actively dripping 7+ hours later (so something in the cooler circuit is still draining down via gravity).
Shop owner came by later without me there and reported it “looks like it’s coming from the filter area” but said he needs to pull the undertray to confirm.
My Questions — The Core of This Post
1. Fill Volume with 400637 Installed
Factory VQ37VHR capacity is 5.2 US qt (4.92 L) with filter change. Stillen advertises “Increases Oil Capacity” but doesn’t publish a specific number anywhere I can find. My estimate based on the 19-row Setrab core + two -10AN lines + sandwich plate is around 0.5-0.75 L additional volume when the thermostat is open.
The shop filled exactly 5 liters total. When I asked about needing more for the cooler, the answer was “that’s all it needs.”
Here’s what I think happened, and I want the community to sanity-check this:
The thermostatic plate keeps the cooler + lines empty until oil temp hits ~82°C. So when the shop filled 5L and checked the dipstick with the engine barely warm, it probably read full or near-full, because the cooler circuit was empty. Once I drove and the thermostat opened, ~0.5-0.7 L migrated from the sump into the cooler circuit — effectively dropping the working sump level by that amount for the rest of the drive.
For those of you running this exact kit: what’s your actual post-install fill quantity? Is 5L total enough, or should it be 5.5-6L?
2. Thermostatic Plate Failure Modes
The “pop” I heard followed by catastrophic oil loss at idle (not under load) suggests a sealing failure that finally gave way as hydrostatic pressure + heat soak combined post-drive. Most likely candidates in my mind:
• Sandwich plate-to-block O-ring (rolled, pinched, installed dry, or incorrectly seated in groove)
• -10AN fitting at the plate or cooler (over-torqued flare, cross-threaded, or improperly torqued)
• Filter seal at the plate (less likely given the correct filter was installed, but possible if the plate’s mating surface wasn’t properly cleaned)
Anyone experienced a failure with this kit? Any specific weak point in the 400637 I should flag to the shop before they start their diagnosis?
3. VQ37 Oil Starvation Risk Assessment
This is what’s keeping me up tonight. I drove for 30 min, multiple full-throttle pulls to redline, with what was likely a 0.5L underfill working-level once the thermostat opened.
Counter-arguments that suggest I’m probably OK:
• Oil temp stayed flat at 91°C the whole drive — real starvation would heat-spike
• The catastrophic leak happened at a stop, not under load — suggests seal failure under low-flow/heat-soak conditions, not pressure failure under load
• 5W-40 gives a bit more margin than 5W-30 would have
• Coolant temp was flat, no signs of any thermal distress
Arguments for paranoia:
• VQ37 rod bearing failure from oil starvation is documented
• I don’t know what the actual sump level was at any point during the drive
• Brief starvation under high RPM can cause damage without showing on temp gauges
Am I being appropriately concerned or overly paranoid? And what diagnostics would you consider mandatory before trusting this engine again?
My current plan for tomorrow:
• Oil pressure test: cold idle, hot idle, hot 3000 RPM (VQ37 target: ~14 PSI hot idle min, ~60 PSI at 3000)
• Compression test on all 6 cylinders (looking for ±10% variance)
• Blackstone oil analysis from the drained oil (or from fresh oil after 500 km) to check for bearing metals
• Preserve all removed O-rings, fittings, and the filter so they can be inspected for failure mode
• Listen carefully for any top-end tick or bottom-end knock on cold start
Anything I’m missing? Any other test I should run before considering this sorted?
4. Filter Mounting Stud
One thing I want to verify tomorrow: the 400637 install on a 2009+ VQ37 should require the short filter stud (the OEM long stud is for the factory oil cooler that’s being deleted). If the shop didn’t swap it, that could explain a filter-area leak — the filter wouldn’t seat against the plate correctly with the long stud. Worth flagging?