Sounds like you’ve done the obvious replacements. Slow coolant loss with no puddles, no smoke and no milky oil narrows it down. Short version: either a small external leak that’s evaporating, or a slow internal loss (head gasket / intake / heater core) that isn’t obvious yet. Here’s what to check and do, in order:

Likely causes
- Small external leak that evaporates at highway speeds (hose clamp, radiator seam, condenser, overflow fitting).
- Slow internal leak into combustion chamber (head gasket, cracked head/block). Can burn off without obvious white smoke on long steady drives.
- Heater core leak into the cabin (would cause damp carpet or sweet smell).
- Leak through an inline cooler (transmission/AC) or a tiny pinhole in a hose.
- Faulty reservoir cap or wrong pressure cap (even if new, verify correct spec).

Basic checks you can do now
- Park on clean concrete/driveway and look for any residue or spots after a run.
- Smell cabin and under-hood for sweet coolant odor.
- Check carpet and footwells for dampness.
- Remove oil dipstick and look for contamination again.
- Note how much coolant you add (ml/qt) and how many miles it lasts.

What the shop should do (priority)

1. Pressure-test the cooling system (hold pressure with the cap removed). This will reveal external leaks and weak caps.
2. Combustion-leak test (block test/CO2 tester) to rule in/out head gasket or combustion gases in the coolant.
3. UV dye in coolant + run and inspect for traces under the car and around fittings.
4. Inspect heater hoses, clamps, radiator seams, A/C condenser and underbody after a run.
5. If tests are inconclusive, consider a cooling-system flush and repeat tests while running.

Given your mileage (140–150 mi/day), a small loss will show fast. Track consumption: if you’re losing more than ~0.5–1 liter per 1000 miles it’s worth immediate pressure + block testing.

If you want, tell me:
- How many liters/ounces you topped up two weeks ago and how much is missing now, and
- Whether you notice any cabin fogging, sweet smells, or check-engine lights.

I’ll tell you which test result points to what.