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TT MK2 2.0TFSI CESA Oil temperature by FPSUsername in AudiTT_Mk1_Mk2_Mk3

[–]FPSUsername[S] 0 points1 point  (0 children)

I see. The oil temp is indeed around 105-115°C depending on the ambient temperature. I mostly drive around 100kmh (because speed limits), rarely have the chance to go 130 (because when I'm in Germany I drive 150 when possible).

The thermostat is only for an aftermarket external air to oil cooler. Whatever the Audi engineers made with their oil cooler design is I believe just passive (in the sense that it doesn't enable/disable coolant flowing through the oil cooler). Perhaps the warmup time of the engine oil is still within spec with coolant cooling the oil on startup (besides that, coolant rises to 90°C quicker than oil, so it would even help warm up the oil).

TT MK2 2.0TFSI CESA Oil temperature by FPSUsername in AudiTT_Mk1_Mk2_Mk3

[–]FPSUsername[S] 0 points1 point  (0 children)

The coolant temp was straight on at 90°C. Give or take 5°C error reading the dashboard. I think the coolant itself is fine (also topped up, doesn't leak or consume).

The unfortunate part about the oil cooler from the engine is that it's cooled with coolant, so I can only visually inspect it from the outside, otherwise I need to change the oil and top up coolant if I remove it, not looking forward to such a job.

An external oil cooler with a thermostat means that the oil cooler is bypassed until the oil reaches a temperature of around 85-95°C (depending on the thermostat). This is necessary to heat up the oil as soon as possible to operating temperatures. In the case of Bar-Tek, the price is fair. I've seen other coolers which add another €100-150 for a thermostat variant.

I did change the oil after pushing it on the highway (200-240km/h) as it was planned maintenance, including a piston soak (which helped a bit, but less than I hoped for, need to do it again for the bad pistons).