Low Oil - No Reason??

[LizB99]

Hi, when my husband checked the oil level recently in his S-Type Jag, it was only just above the min. mark. He topped it up to the max, drove it about 300 miles, checked again, and it was below the MIN! As he could see no oil leaking onto the drive, he assumed the worst - that he must be burning oil. (He's had the car 3 years, and never had to top up the oil between services before)
He took it to the local dealer, who spent ages checking it over, but could find no problem with it!
It all seems a mystery - just wondered if anyone else had experienced anything similar?
- (He has recently started travelling a lot more with his work, and so does a lot more motorway driving, so we're wondering if that could be why its started drinking oil?)

[LizB99]

Thanks for your response zacsaster.
Yes the engine was cold, (overnight), and the car level.
Its done 57,000 miles, the last service was at 50,000. Its being serviced every 10,000 miles, and as I said before, never needed topping up before between services. (Although that was mainly over pretty short journeys of around 30 miles a time, as opposed to the much longer, motorway journeys he now does.) Its a 3.0 ltr V6 petrol engine.

[Teddio]

There are two simple tests you can perform to check whether the engine is burning oil:
1. Drive down a long descent without touching the accelerator pedal. Floor the throttle pedal for a couple of seconds. If you hear a knocking noise and see smoke from the exhaust pipe it is likely that the valve guides or seals have worn or failed,
2. If smoke appears under heavy acceleration (normal for a diesel engine) it is likely that an oil control ring has failed.