The analysis of the Jaguar XJS oil problem was abysmal. They were equating the fuel gauge to the dip stick measurements, whilst the owner's concern was the reading of the oil pressure gauge, thinking it related to oil level. So they need to get that car back and check the oil pressure.
The Jaguar E-type air filter they replaced the outer mesh but did nothing about the inner mesh or the fine filter sandwiched between the two.
In all, there are now 2 Jaguar engines which lined up to seize.