I have had my 04 Astra Diesel for a couple of months now but over the last week, it has been sluggish to start - as if the lights had been left on. This has not improved even though I have since done 500 miles- with few short hops. The engine cranks slowing for 3 or 4 seconds then starts & runs fine. No engine lights other than the oil light which stays on for 4 seconds after the others. Oil level is fine and car seems reasonably well looked after. Before last week starting was almost instant.
The battery is a Vauxhall one and looks like a 400a maintenance free unit - probably the original.
It read 12.7 volts when checked today but I am not sure if I can recharge it. The reading said it was 83% efficient.
I reckon it will fail to start at all sooner rather than later. Any advice please?