Knocking sound

[1996FordExploder]

I have a 1996 Ford Explorer V6 4.0 it has 252k miles. Just recently it started making a knocking sound. It's louder when the vehicle is still, but when the vehicle is in motion it doesn't really seem to get louder. A local mechanic said he thinks that the motor needs new rod bearings. A buddy of mine also said it needs new rod bearings, crank bearings, or possibly main bearings. I was wondering if any of you on here knew of common engine problems with this model of Explorer.

I have been using 10W-40 oil and I recently changed my oil and used what the car actually calls for which is 5W-30 so I don't know if this could be the cause of the knocking sound or if it's just started by coincidence. That's why I decided to ask people who have more knowledge on mechanic type stuff than myself. Any feedback would be appreciated.

Thanks, Jarrod

 

[ron3110]

A 252k mile engine should use 20W50. It is a thicker oil and will help in filling the gaps due to wear. You may also use oil additives to help reduce the knocking. I tend to believe that the answers you have received are correct. 5W30 is for low mile engines. Also use regular gasoline 87oct.

 

[1Aauto]

I think it just may be due to the mileage.