Classic/Antique Car Repair: oil, weight oil, cruise speed

Question
I have a 67 xke 4.2 roadster-what weight oil do you suggest I use? Not sure of the exact mileage

Answer
Hi Dale,
If it were mine, I would use 20-40 in warm weather and 10-30 in cold weather. Be sure to change the oil and filter every 3000 mi. At the Jag dealers I have worked at we recommended Castrol.
With that weight oil and the oil temp up you should see 25 to 45 PSI oil pressure at idle and 45 to 60 PSI at cruise speed.