I have a 2001 318i Touring E46 with around 130k on the clock. In the last 8-12 months the oil consumption has been increasing dramatically, but there is no sign of a leak from underneath - no oil puddles left on the drive overnight.

In the last week or so it's also been guzzling water, again with no sign of puddles underneath, on the engine or in the belly pan. The water/radiator light is on almost all the time, and I can put over a litre of water in after only a short drive. It's been pressure tested and is holding pressure as it should. There are no big clouds of blue smoke from the exhaust, just occasionally a fine white vapour.

Is this evidence of a blown head gasket? Is it worth using something like Steel Seal as a preventative measure (I'm aware it's not a long term fix).