i was at a buddy's house last night and when i started up my truck to leave and when i was driving away my friend called me and said to put oil in my truck because it was knocking, but you don't hear it all the time but it defiantley knocks a little bit when it starts. And its filled all the way with oil..Whats up with that? Is that Lucas heavy duty oil any good? what should i do its a 1990 F150 300. Any responses would be great..

 

If it knocks mainly when it's cold, then you're probably just hearing the normal wear 'n' tear on your mechanicals. Over time the clearences in the lower end will loosen up from wear and you'll get some noise. I'd guess either you are hearing piston slap or some slight rod knock due to wear. When it's cooler, the clearence will be at it's greatest and allow either the piston to "slap" at the top of the cylinder due to the rings, or the rod bearings have worn slightly outside the normal tolerance range and the rod is "walking" a bit. Once the engine warms up a bit, the clearences tighten up again and the noise goes away. Pretty normal for an engine thats older or high mileage. You could try something like a Lucas heavy oil or a high mileage specific oil, but they may not completely get rid of the noise.

If you mainly hear it only when it's cold and it doesnt bother you a lot, just keep up with the regular oil change intervals and keep driving it. I would guess the engine will probably last ya quite a bit longer anyways. The only way to completely cure that noise anyways, would be to rebuild/replace that 6'er.

 

Hey GDDYUP thanks for the reply man, i won't let that bother when i start it up...and yes it does it mainly cold but then it will do again after it was ran like an hour before. I'll try the Lucas next oil change ...thanks for all your help....Jake