I had a similar situation with my Subaru 1800 cc H4 a few years ago.
My solution for many years was to burn 91 or 93 octane fuel.
At 175,000 miles, I had to replace my radiator due to flow problems. To my surprise, after I installed my new radiator, all pinging ceased even using 87 octane fuels.
Please note, I didn't see a significant reduction in coolant temperature on my dashboard oem guage.
Perhaps, you might try a cooler thermostat and see if that helps.....
Good luck.
My solution for many years was to burn 91 or 93 octane fuel.
At 175,000 miles, I had to replace my radiator due to flow problems. To my surprise, after I installed my new radiator, all pinging ceased even using 87 octane fuels.
Please note, I didn't see a significant reduction in coolant temperature on my dashboard oem guage.
Perhaps, you might try a cooler thermostat and see if that helps.....
Good luck.
