I have a 1989 XJS V12. What type of oil should I use, synthetic or conventional?

 

You can use either dino or synthetic. The book calls for 20W50. People (and I) have used extended range 5W50 (Castrol) for year round driving with no problems.

 

I'm debating either Castrol GTX 20W-50 or Mobil 1 15W-50. Previous oil change Castrol Classic 20W-40 was used but the car only has 37,000 original miles on it. I think it could benefit using the Mobil 1 and maybe it would quite the engine down some. Thoughts?

 

Just make sure that you use motor oil Non synthetic.

 

Is there a reason not to use synthetic? It seems to me that the V12 generates a lot of heat and that synthetic would better handle the heat.

 

I had 2004 XJR I put Castrol full synthetic in it and drove it to my mechanic to check some electric issue to change the rear module. He was working in Range & Jag dealer for about 30 years. He spend about 5 minutes telling me why to change it to non synthetic he was saying about the seals and a lot of things. Just to make sure that he wasn't looking to up sale and adding money to my bill. He told me he doesn't have time to change my oil and begged me as soon I leave his shop I go and buy Castrol non synthetic and change the oil. He even told me If you couldn't find Castrol it ok to se other brands but non synthetic.

 

For handling the heat look for a better radiator & fan system.
try to see a good all aluminum Radiator maybe 3 or 4 core. I installed to my classic C3 corvette and it's a big relieve you I can go from MD to CA with no worries. I use Champion radiators High quality low price & life time warranty.

https://www.ebay.com/itm/3-Row-All-a...4383.l4275.c10

https://www.ebay.com/itm/3-ROW-ALUMI...4383.l4275.c10

https://www.radiatorexpress.com/prod...aia_id=1178793

 

Thanks for the advice. I'll have to look into what you suggest because in Central Virginia it can get hot here. I already put in a 180 degree thermostat and that seems to have helped.

 

Yes I did that to They sell $6.00 thermos but I bought the $26.00 Coper one.