I have made the mistake of letting brand name shops do oil changes on my 2011 Mazda3 2.5L and they have been putting what I am assuming is thier regular generic 10w40 or 10w30 at $2.95 a quart. I decided to get the equipment to start doing the oil changes myself and noticed the engine oil calls for 0w20 synthetic... Which I am assuming the car came with. Long story long, is this doing any sort of damage to my engine? Should I be trying to get ahold of the shops and get some sort of fix done?

Ive got oil changes done every 3k at 3 different shops since I have owned the car and I have 27k miles on it.

Thanks for your replies and your time,

Axel

 

Do you not keep your receipts? It should say on there what they used. If it was synthetic it would also be expensive. Without receipts, you will not be able to claim warranty, especially on a new car. I recommend oil changes at the dealer for first while at least; this way you don't have to worry about receipts as it is in their records.
The oil cap is more than likely stamped with oil type needed (or at least viscosity---0W20), so they would put the same in unless you ok'd otherwise.
Synthetic is better for your car, especially in winter. Damage---depends on oil viscosity used.

 

I have a couple receipts, and like I said they were charging $2.95 a quart which is definitley not how much synthetic oil costs.

The reciept does not specify the viscosity if oil used