Hey Scotty! 

I have a 2019 F150 5.0 V8 with the 10 speed automatic transmission 4x4. It has about 50,000 miles on it. I purchased the vehicle used from a dealer March 2020. According to the documentation I can find, I am the second owner. I’m in the southwest portion of the country.

The issue I am having is under low to moderate acceleration, around 20-30 miles per hour, I am hearing a rattle/metal ping noise from under the engine area. It gets worse if the truck is going up any incline at the same speed. 

I’ve brought the truck to 2 separate Ford dealers. The first told me that the engine is just noisy and to drive my truck harder. I laughed and never went back there. The second dealer told me that the 5.0 V8 runs at a higher compression and if I run 87 octane gas, I could experience preignition detonation which they believe is the noise I hear. The recommend me use 89 or 91 octane and that should eliminate the noise. 

I have done some testing with running 87 and 89 octane in the truck and have noticed that with 89, I do not hear the noise as much and as loud. I also have read that preignition detonation is not good obviously.

I watched your videos about the different octane fuels and am just curious to your insight into this issue combined with the octane levels. Any thought? Thank you!