Well I was ASSuming he had a radiator fan. If he has no fan, he should add one of course.
If he's overheating in stop/go traffic, my guess is inadequate airflow across the radiator is the problem. In this case, adding an oil cooler is not going to increase air flow across the radiator.
If he's overheating at idle, then he needs a good fan/fan shroud setup to improve airflow at idle.
If he's overheating at low speed cruise, then shrouding needs to be added to increase the pressure delta across the radiator.
If he fixes the overheating problem and then finds his oil temperatures are higher then they should be, he should add an oil cooler to cool the oil.
Does this sound crazy?
He has a shitty slimfan zip tied to the core. Shrouding makes a huge difference, a fan zip tied to the core doesn't do shit, he needs a real fan and a real shroud.
The way its setup right now the fan isn't pulling air across the core, thus no cooling effect at idle so even when his car does move the little bit in stop and go traffic he trying to overcome serious heat soak.
An oil cooler with a fan will drop 15-20*F off of his oil temps and will also help with his cooling.
If you see my build thread, I've got pics and info of where I put a ford fan inside a miata fan-shroud. Made a big difference in airflow over the stock fan in the stock fan-shroud, and costed 6 bucks and an hour, and I have an OEM high quality fan, not a made-in-china knockoff bullshit fan. Fan shroudings is important, and is often neglected. The 99-00 miatas had excelent fan shrouds, but the fans themselves are just average.
IMO, urban could put a better water pump, super heavy duty oil cooler, water-wetter, etc and each one would help "a little", but none address the root problem. I'd be damned if I'm gonna spend time/money doing BS stuff before doing the easy/obvious stuff.
The reason I put the Ford fan on my car was because the temperature of the freon exiting the condenser at idle was 50-60*F above ambient at idle. This translated to no colder then 48-50*F A/C on max at ilde on a 95*F day. The new fan dropped condenser exit temps to <20*F above ambient, and now the A/C air falls to 42-44*F (40*F expansion valve limited) at idle. Before and after datalogs show the fans run about 15 seconds less then before to pull coolant down from 200*F to 197*F, so that improved also.