As Iggy said, Stick to 10w40 Semi. If you go for something thinner, thats when your Rear-main will probs start leaking. Mine did on my old 850 T5 !!. DB.

ta, I had kinda figured as much but just wanted to make sure.

always use fully synthetic on a turbocharged car if you want the turbo to last. find oilman's posts. prob the reason your car is smoky on boost tom, is the fact its had cheap oil in it all its life and not mobil 1. check over on VPC about the oil people use as well. I am fully aware that it can cause RMC leaks and weeps, however if you put a can of seal rejuvinator in you are 95% going to be fine and your turbo's life will be significantly lenghtened.

so why would Volvo recommend 10/40 semi? Surely they know what is suitable for the car they designed and made? No? The turbo has done 139K, it isn't smoking and had new inner seals 18K or so ago. If it really was that bad for the turbo, it would have needed a new one by now as many cars with this mileage have had to have.

hi have to say my 850 has now covered 200 k on semi synthetic from new so i wouldnt have to many worries, of course a full synthetic is in theory superior,...... but in practice maybe not that superior!

semi will be just fine for your t5, although i like a 5w just to be sure i am getting the best for my turbo as early as possable without jepardising seal security...... semi is good enough for the t5's despite what anyone may or may not say on the vpcuk site and a mineral 10w 40 is perfect for the n/a versions..... regarding seal rejuvinators, i understand that forte do a product, which i was very sceptical about although several people did say it had worked for them...personally i cant see it.... cheers jod