OK, just got the 940T at 220,000. miles and changed to synthetic. I did a 50/50 blend for the first oil change, then the full synthetic. The cars original mechanic told me to 'drop the oil right away and go back to 10W30' or risk creating oil leaks. According to the forum posts, I am doing the correct and smart thing to upgrade the oil in this volvo. I love the car, any advice would be welcome, rooster11

 

Synthetic Oil does NOT create leaks, however if your seals are old and somewhat weak, then they will find the weak spots in your system and sometimes leak. Essentially anywhere in your system where the seals aren't making a full closing seal, then with the slippery nature of Synthetic, it will run thru. In all honesty, some use this as a test to see what seals in the system need to be replaced. If your seals are good, then you shouldn't have any issues with them. if you don't find any leaks, then drive like you stole it!

 

thanks for the reply, the timing belt, water pump, seals were replaced at 207,000. I just ordered a lower radiator hose and thermostat last night. Now, will a K&N airfilter be worth the expense as this car has a flat filter. I use them in all other vehicles with noticable improve gas mileage?? thanks, rooster11

 

Synthetics will cause no issues, but I personally question whether they are worth the extra money on older engines. The wear is already there, engines wear faster as clearances open up, so just use a high quality mineral oil I say.

Regards, Andrew.