I use 15w40
Yes, you can mix conventional oil with synthetic oil with no problem.
10W40 or 15W40
15w40
A diesel engine would use 15w40 a gas engine could use 15w40 or 10w40
I use 15w40
Total FLUIDE DA available at the Peugeot or Citroen dealer
15w40
12 quarts of 15w4012 quarts of 15w40
Total Fluid DA, available at your peugeot dealer, anything else will cause problems
15w40 with an api rating of cj4
15w4015w40