tyre pressure loss (Vauxhall Astra 2005)?

No. You have a leak.

That's a small loss but no leak is an acceptable one.

The tyre might not be sealing fully on the rim or the valve may be slightly faulty. It's also possible that the rim has been damaged or that the inside edge of the rim has corrosion and both of those can prevent the tyre from making a good seal. Another possibility is that the tyre is old; after about five years the rubber compound has significantly hardened from when new and the tyre can fail to maintain a good seal with the rim..

It's probably not worth the cost of having the tyre removed (possibly replaced with a new one), a new valve and refitting, so unless it gets worse just maintain the pressure by topping up every week/fortnight. You should also ensure that the valve still has a dust cap as they do have a very slight indirect role in maintaining the tyre pressure. You can also try letting the tyre down completely, rolling the car forward one complete tyre revolution, and then re-inflating the tyre. That can re-seat the bead on the rim, but it can also make the problem worse and so sometimes needs a few attempts.

All tyres leak, end of story.

If the conditions you tested the tyre are the same (cold tyre and roughly the same ambient temperature) then 1-2 PSI is normal. I'd be more worried with 4 Psi leaking - that's a slow puncture.

Take the wheel off and double check it for nails/tears just in case.

You should check your tyre pressures weekly and in the morning or before you start driving.

Check and make sure the valve is tightened and that it is not leaking any air.

Personally I would also check to make sure a small tack/nail has not penetrated the tyre causing a slow puncture to develop.

Best to take a few minutes carry out the checks and at least set your own mind at rest - happy motoring.

Best regards

I really wouldn't sweat about such a small difference. I check tyres on 3 cars once a month and frankly i'm disappointed if I don't put in about 6 lbs in total for 4 tyres. We are always reading about doing checks on our cars but many motorists don't check anything between services and some never touch their cars or even service them. Congratulate yourself. Your car will be more economical, Your tyres will last longer and your car will handle better.

Have a look round the tyre, you more than likely got a small nail in it

If the outside temperature remains close as it was when you last checked the air pressure then it should not lose any in that period of time. If the temperature has dropped considerably since you last checked the pressure then all the tires would seem a little low as the air has become denser.

It will say the tyre pressure on the drivers side door

No.