I was using 20w50 (Castrol Syntec) in my 1996 XJS AJ16, but now
winter is upon us and I swapped it out for a 0w40 Mobil 1.

I checked the manual and it doesn't show what the range is for a 0w
oil. Does anyone know what the max recommended operating
temperature is for the 0w40 oil? I just would like to know how
long I can keep it in the engine. I'm assuming I'll put the 7,500
miles I need before it gets warm enough to worry, but I would like
to know what the recommended operating range is for this oil in the
AJ16.

Thanks!

 

I'm not sure if I have a handle on replying with attachments but this PDF should have all your answers.

 

Thank you. It doesn't seem to acknowledge the existence of the 0w40 just yet.

The 5w40 looks good from 105 degrees on down. I'm thinking that the 0w40 isn't going to be much different.

I won't be running anything lower than a 40 weight in this car.

I don't understand why the 5w40 weight would top out at 105 degrees, doesn't the engine run hotter than that typically?

 

Proper oil viscosity has been a topic of discussion for many years and will continue for many more. I had a 93 xjs 4.0 and put 5w-30w and on many occasions I would see a little blue smoke out the exhaust and would hear a little engine noise on cold starts. Changed the oil to a higher viscosity and all was good. My 95 xj6 4.0 the same thing. I recently went to 10w 30w in my 99 xk8. I should note that all three cars had over 100,000 mi and all were well taken care of. I am attaching a link to Bob the oil guy http://www.bobistheoilguy.com/cms/index.php This information will help you to decide on the oil you should be using. Good quality oil should not be compromised along with the understanding that your car has a few miles on it and the temperature range you live in. Pulling this together you should be in a position to select the right oil. Good Luck!

 

The numbers refer to ambient air temperature, not engine temperature. You should be able to find one oil that suits your climate year round.