I think this might be normal but just wondered why it happens.

I started my car earlier when it was stone cold and somehow managed to forget that the ignition was already on and neglected to use the glow plugs at all. To my delight the PD engine starts flawlessly even at -0.5C and NO glowplug heat, but for the first 20-30 seconds the engine idled at 1100rpm instead of the normal 950 or so.

Anyone know why the car does this?

Its normal, aint it like an old choke

Its normal, aint it like an old choke

Didn't think diesels needed a choke

Cant say I ever noticed mine do that.

Cant say I ever noticed mine do that.

Nor me.

its all part of the cold start device which raises the idle speed to enable a smooth tickover before the engine warms.

My Astra Diesel used to go to 1300rpm for a short while then drop down to 950rpm.

Never noticed mine do that either.

My BLT runs faster on idle when it's really cold out.

Yeah mine too and mine's BLT. Only does it if it's really cold. Nothing to worry about.