Think your diagnosis is correct, timing chain/tappets just pressurising on start up. Doesn't sound like anything to worry about as long as rattle goes quickly.
These engines are sensitive to Oil type and viscosity. I only use a good quality fully synthetic 5W/30 Oil that meets the latest jag spec. I use GM 5W/30 (because I can get it cheap!) low ash Oil, that exceeds all Jag, BMW, Merc specs. Made by Mobil I think. Don't be tempted to us Halfords Comma oils etc.
Keep level at max on stick, dipped with oil hot after allowing no more than 3 minute drain down. I always used to dip the oil on a morning but was told this is wrong for modern engines using low viscosity oils as they hold a good half litre up in the top of the engine. Guy who told me this is jag/lotus trained engineer so think he'll be right.
He also said I was wasting my money using engine flush or any additives as these high spec oils do the job even with 15k mile change intervals.
4.2 V8 Engine
in 2003 Onwards XJ
Posted
Think your diagnosis is correct, timing chain/tappets just pressurising on start up. Doesn't sound like anything to worry about as long as rattle goes quickly.
These engines are sensitive to Oil type and viscosity. I only use a good quality fully synthetic 5W/30 Oil that meets the latest jag spec. I use GM 5W/30 (because I can get it cheap!) low ash Oil, that exceeds all Jag, BMW, Merc specs. Made by Mobil I think. Don't be tempted to us Halfords Comma oils etc.
Keep level at max on stick, dipped with oil hot after allowing no more than 3 minute drain down. I always used to dip the oil on a morning but was told this is wrong for modern engines using low viscosity oils as they hold a good half litre up in the top of the engine. Guy who told me this is jag/lotus trained engineer so think he'll be right.
He also said I was wasting my money using engine flush or any additives as these high spec oils do the job even with 15k mile change intervals.