XC70 Regular 91 RON or Premium 98
My parents bought a used first owner XC70 2003 Volvo AWD Turbo Cross Country. I checked on the manual and I see it uses RON 91, 95 and 98.
The manual recommends to fuel the car with 98 Premium which cleans the engine. I called Masons and they said you can use RON 91 because it doesn't harm the engine but the previous owner use Premium 98.
So, should I allow 98 to keep the engine clean or use 91 to save money but builds up the dirt.
VOLVO XC70 2003 AWD 160,000KM