[bracka]

I conducted a small experiment on my BMW 530xd 2021 (G31 LCI) to determine how effective the auxiliary heater is at warming up both coolant and engine oil temperatures compared to just starting the car or starting to drive immediately.

Test Details:
Data logging via BimmerLink.

Test 0: No use of auxiliary heater. The engine was started and left at idle. Ambient temperature was -5°C.

Test 1: Preheating with auxiliary heater for 15 minutes before engine start, then left at idle. Ambient temperature was 1°C.

Test 2: Preheating with auxiliary heater for 15 minutes before engine start, then left at idle. Ambient temperature was -3°C.

Test 3: No preheating with auxiliary heater. Engine was started, followed by mild driving. Ambient temperature was 0°C.

Data and charts are available here: https://docs.google.com/spreadsheets...it?usp=sharing

Observations:

Coolant Temperature: Using the auxiliary heater for a 15-minute preheat demonstrated minimal increase for the coolant temperature compared to no preheat at idle. Within about 5 minutes, the preheated coolant was 5 to 10°C warmer. However, actually starting to drive resulted in the quickest and highest temperature increase, reaching 58°C at 3 minutes 50 seconds while other tests had only reached ~30°C at this timestamp.

Engine Oil Temperature: For engine oil, the auxiliary heater showed no significant effects. In all tests, besides driving, the oil temperature increased only by 2°C within 5 minutes. Driving 5°C in 5 minutes.

Conclusions:

Based on my tests, the auxiliary heater does not significantly contribute to heating coolant or engine oil under moderate winter conditions. You are better off just starting to drive mildly to get oil up to temperature. Auxiliary Heater primary practical benefit appears to be cabin heating and improved comfort upon entry.

I'd be interested in hearing your experiences or if you've observed similar outcomes!

[Knifeedge2k1]

Originally Posted by bracka

I conducted a small experiment on my BMW 530xd 2021 (G31 LCI) to determine how effective the auxiliary heater is at warming up both coolant and engine oil temperatures compared to just starting the car or starting to drive immediately.

Test Details:
Data logging via BimmerLink.

Test 0: No use of auxiliary heater. The engine was started and left at idle. Ambient temperature was -5°C.

Test 1: Preheating with auxiliary heater for 15 minutes before engine start, then left at idle. Ambient temperature was 1°C.

Test 2: Preheating with auxiliary heater for 15 minutes before engine start, then left at idle. Ambient temperature was -3°C.

Test 3: No preheating with auxiliary heater. Engine was started, followed by mild driving. Ambient temperature was 0°C.

Data and charts are available here: https://docs.google.com/spreadsheets...it?usp=sharing

Observations:

Coolant Temperature: Using the auxiliary heater for a 15-minute preheat demonstrated minimal increase for the coolant temperature compared to no preheat at idle. Within about 5 minutes, the preheated coolant was 5 to 10°C warmer. However, actually starting to drive resulted in the quickest and highest temperature increase, reaching 58°C at 3 minutes 50 seconds while other tests had only reached ~30°C at this timestamp.

Engine Oil Temperature: For engine oil, the auxiliary heater showed no significant effects. In all tests, besides driving, the oil temperature increased only by 2°C within 5 minutes. Driving 5°C in 5 minutes.

Conclusions:

Based on my tests, the auxiliary heater does not significantly contribute to heating coolant or engine oil under moderate winter conditions. You are better off just starting to drive mildly to get oil up to temperature. Auxiliary Heater primary practical benefit appears to be cabin heating and improved comfort upon entry.

I'd be interested in hearing your experiences or if you've observed similar outcomes!

But that’s what it’s for, to warm up the cabin, not the engine. If that was the goal, get a block heater

[d4700]

Thanks for the test. I had been wondering about this for a while.