[RedDevil]

It was just to see if it had any effect at all. It was very strategically placed.

And it did have an effect; it did indeed raise the intake temperature by a few degrees.
Also, seemingly surprisingly, it made the engine heat up slower. The cold engine light only went out when I passed my kids school, at nearly a mile.

Today saw almost the same circumstances as yesterday, same temperature but just a little less wind.
Without the hot water bottle the cold light went out way before I passed the school, in about a kilometer (0.6 miles).
I'll test tomorrow again with the hot water bottle and see if I can replicate the effect.

I can imagine that the slightly hotter air helps the combustion, burning the fuel slightly earlier, making it more effective therefore needing less of it.
But I cannot explain why the difference would be so big.

Up till now it was a one-off, more testing is needed, now with an added research goal: Does a raised air intake temp slow down engine warm up? Or was this a freak incident?

I'm enjoying this