Valve knocking when I put regular gas on my 2002 F150 I hear valves knocking when the truck is cruising and then I switch back to higher octane is fine ,what can I do ?

If it sounds like a sort of knocking noise, it could be that you are using a gas with to low of a octane level. See what happens if u put higher grade gas in or go to auto parts store and try a 5 dollar bottle of octane booster on your next fill up. If that quiets your noise that could be your problem.

87 octane--this least expensive one

If it has a lot of carbon & other problems
try 89 octane if it knocks

Wrong spark plugs?
Make sure you use iridium plugs by NGK or Denso.
NGK V-Power Plugs BKR5E-11

Carbon Buildup?
Get some Techron and run several tanks

Wrong Octane?
Your engine should use regular gas. But you might be getting some low grade gas. You can try using a higher octane fuel. Or try adding a octane booster.

The only reason to run higher octane fuels to to reduce the chance of (engine ping) or (engine knock).Try the regular gas(dont completely fill car) and take notice under hard acceleration if engine makes a pinging noise.If pinging happens then add some high octane gas to compensate for regular.Unless this is a modified engine the regular gas will not do any damage it will result in pinging and loss of fuel milelage.

No it will not hurt and there is no reason to switch to a higher octane gasoline with this engine. Certain engines in Corvette, Cadillac, etc with special combustion chambers utilizing different types of metal for performance need higher octane gasoline. Your v6 does not. If you hear knocking, have your valves checked and make sure you oil pressure is good. If you switched for no reason, switch back and save yourself $$$

87 OCTANE REGULAR UNLEADED.

do not use any fuel additives at all. and only use 87 octane fuel nothing higher. 4.6 and 5.4 ford engines do have a pinging sound especially with a load. but it is normal

If you mean regular as in to the octane rating, is yes. The octane rating for your car is 87 octane, you could use the higher rating with out harming the engine. But that's just money out the tail pipe. Good luck and hope this helps.

Fuel comes in different grades due to octane levels, the higher grade the higher octane, the higher price. If you have the owners manual or window sticker, you would see that the car was probably made to run on 87 octane (regular unleaded), I have been through the different octane levels for more than 30 years and I have decided that the cheapest runs as well as the most expensive. The higher octane will sometimes cause an engine to ping or rattle under acceleration, if this happens to yours go back to the cheap stuff and everything will be fine. That is my opinion, others may differ, but I run my BMW on the cheapest I can find and I still get 31 MPG hwy.

The pinging noise that you hear is detonation occuring in one or more of the cylinders. The dealer suggested to move to a higher octane inorder to prevent this because the higher the octane the higher the prevention of Detonation.

The Probable cause of the pinging, would be that you refilled with a bad batch of gasoline. Premium should be used in this vehicle no matter what. Due to the clearances of the heads and valves in the motor. And also due to the material used to make the cylinder heads, if severe detonation occures then the valves could be damaged.