After three months ownership of my 1985 XJ6 Series 3 sovereign (RHD); and after completing two long distance round trips and various short day trips, I thought that I would note a few experiences and upcoming "tasks". I purchased site unseen and paid more than I wanted but less than asking.
1. Fuel consumption is 13L/100km (18 mpg US) using 98 octane. It took some explaining to my wife that it did not cost what she thought it did in petrol for my first round trip. She included the first full of both tanks, from empty to full, and I finished the trip with two full tanks.
2. Oil pressure 60psi, temp just below 90 degrees C when going 100km. Oil pressure drops slightly to 45-50psi when going 50km.
3. It did leak a bit of oil on my garage floor, but after a few long trips and the oil on the half way mark on the dip stick it has stopped. It does have a healthy oil film on the underneath of the car.
4. It has had upper head and valve work done according to records within the last 2 years. I assume tappets were set correctly then and have not come loose. I can not feel or see a tappet retaining shakedown plate installed through the oil filler cap. I will buy and install one myself soon (after reading strong recommendations to fit them). The engine could do with a general tidy up and few parts painted or polish at some stage too.
5. Green coolant. Not sure if I read some where not to use the green coolant as it isn't good for the aluminium heads? I will research and flush if required. All the hoses look and feel good.
6. Engine Belts need replacing asap. I have a spare black fan that came with the car with correct OEM part number. I will replace the current white fan when I do the belts.
7. Radio and only the front passenger speaker works. I will check connections at some point or replace all speakers. Tape player is not working (it is a shame as my regular journey has an hour that not radio frequencies are available and I still have a few good tapes). I will pull it out and see if it is repairable or broken for good.
8. Automatic Aerial did not fully retract. The aerial had been bent and cracked prior to my ownership. I pulled the whole unit out and was able to force it down and reinstalled it. I cut the nylon cord and disconnected the aerial motor so it will always stay down. I intend to install a hidden / stealth aerial in the boot.
9. Trip computer wasn't working. Changed fuses and after battery fully charged it now works. The data doesn't make sense to me, but I only use the clock.
10. Wet front passenger footwell. I am fairly sure it is just a blocked air con drain and not rain water leaking in, as I removed the carpets, dried the area out and drove 3hrs home in sunny conditions. Area under carpet looks pretty good still. Carpets and underlay could do with replacing at some stage. I reached under the car and cleared the drains. Going for drive tomorrow so hopefully this is sorted. Floor pan looks okay.
11. After removing carpets and central side footwell panels, I noticed two wires with inline black fuse holders, connected to a brown wire and pink/white wire. Not sure why? They can stay until I check out the wiring schematic to find out what the brown and pink/white wires are.
12. Cold air doesn't seem to make it through the back via the rear louvers. I need some one else to drive for me to sit in the back and check it. (I haven't tried the heater yet, as it is really hot and humid still).
13. No ram air. I think it is a design flaw having no ram air and only air con, especially when I have a problem with my drivers window (see below). I will make the modification to allow ram air via the head lights mention on this forum and others.
14. Front Passenger interior door light not working. All other interior lights now work after replacing fuses and wiggling a few bulbs.
15. Drivers window slows / stops on the way up. I need to help it up when it gets half way.
16. Map light lens missing. I will keep an eye out for one...
17. One rear fog light lens missing, somehow it fell off in transportation. I found a lens only, after a bit of searching online. The bracket / wires inside the lamp unit were also broken / loose. I fixed these and fitted the lens. I have now purchased a pair of new (old stock) fog light lamp units for sale for not much more than what I paid for just a lens. The two lens I have currently fitted are a noticeably different shade of red and my repair to the lamp unit may not last. The price for the pair was a third of the price I have seen one lamp unit for elsewhere. I am already collecting spares!
18. Corrosion around one of the rear passenger window frames on bottom rear corner. This is the only place I have found corrosion that I need to urgently attend to so far.
19. Bonnet or hood popping open while driving. I adjusted one of the hood prongs out half a turn to stop it and the other side needed adjusting in. I hasn't popped since. It was very annoying on my long trip, if only I remembered I had a tool kit in the boot.
20. Front passenger mirror glass loose.
21. Front passenger door lock loose.
22. Drivers door lock could be opened using any key or flat blade. It will be parked in secure places for awhile.
23. Water spots on black paint. It is hard to stop getting water spots, as where I live it can be hot summer, then be like the middle of winter and then half an hour later full hot summer without a cloud in the sky again. I will need to do a full cut and polish after trying a few liquid products that claim to be as good as a full deep cut.
24. All interior in good condition for age.

We are happy with our car and intend it to be a long term vehicle. With a little bit of Italian ancestry in my mix, I think the styling of the series 3 appeals to me. There is plenty of time to get to the above tasks and any ongoing maintenance carried out.

I feel like an Engineer, I know the theory and have read a lot, but I haven't used a spanner on a Jaguar in anger yet. (I hope not to offend any Engineers out there).

My two young sons and daughter have named our car Conish Cash (I wanted to call it Johnny [Cash]). I didn't want a project car at this stage, due to young family, other things going on and house DIY projects; but I can handle the above tasks over time. It is a step up from previous non luxury British cars I have owned. I am already trying to figure out when I will be able to buy our second Jaguar.

I debated putting the long post up, but in the end it is a good record of my ownership for me and it is what the forum is about (I think in my limited experience). If I come across any thing interesting when working on my above tasks or any others I will post separately.