I have a well maintained 2009 Mazda6 S Grand Touring with the 3.7L V6 Engine (Ford Duratec) with 109k miles on it. I am the original owner of the vehicle. I've always had the engine oil changes done (on time) at the Mazda dealer and they've always used the semi-synthetic oil. Last time I took the car for the oil change to the Mazda dealer, they used full synthetic oil, which they didn't inform me of ahead of time and I only found out when time came to pay the bill. I was quite surprised and upset over it as I heard that you shouldn't switch to full synthetic this late in the game. But their explanation was that now they only stock full synthetic oil. So now I've driven the car on this oil for about 3000 miles and I haven't noticed any issues (no leaks). My question is should I go back to the semi-synthec or continue with using full synthetic going forward?
It's up to you. I personally have never had any bad experiences even going from conventional to synthetic and back (although I'm sure others will disagree). I'm sure it's even less of a gamble going from semi synthetic to full.
Don't worry about it too much. As long as it's clean oil that's the right viscosity, that's the most important thing.
The main issue with semi-synthetic is how much full synthetic is in the oil? 50% 5%? To me either go with natural oil or full synthetic. The blended oil is just a money grab. I only use full synthetic in my vehicles. I know it's better for the engine and for me it's not that expensive. In short, I recommend full synthetic
Just watch your oil level. If you don't notice much of a loss you're fine.
either is fine
