Hi All, after a bit of help with my S4.

I recently bought a S4 (4.2 V8) model which has a very recent top end rebuild and new timing chain (4k ago). It's done 184k and can also runs on LPG (not used much). I do a fair amount of miles for work appointments.

Driving around town and say 30-45min on B and A roads it doesn't show a low oil warning and I can probably do 1k without it asking. However, when I get on a duel carriageway or motorway chipping along at 70-80 at a constant rev position the Low Oil Warning then comes on. This has happened twice now. I top it up a touch (not much as can't really tell the level when hot, but probably 0.25-0.5ltr) and the light will go out for about 50 miles and then back on. I then continue to drive as I am happy there is oil for the next 200 miles. I let it cool down over a day and then the dip stick is saying full. The oil grade is 10/60 fully synthetic race oil. I do the long drive back again and the same happens. The next day I check it again (Light on and oil is low) and I top it up again with 0.25ltr as that was all I had left and have done nearly 200 miles with no light on A and B roads or town driving.

Do I have a dodgy sensor? Is the oil grade to thick and not circulating well enough to go back in the pan? What oil is recommended for this mileage? Very confused about it. Before I left to travel 300 miles all levels were perfectly topped up. Light came on after 70miles on duel carriageway, and has only ever come on Motorways or duel carriageways when cruising consistently at a fixed rev band.

It does all have a secondary air pump fault but think this is unrelated?

Apologies if I haven't explained it very well.

Thanks
Dave