you are right about it, but you can't just jump from standard oil to synthetic. you have to break the synthetic into it by using synthetic blend for 3 or 4 oil changes before switching to straight synthetic. Also as 2002XTREME said; you can not go back to standard oil after the synthetic has been ran through. Its like growing up, you can't go back no matter how hard you try.

 

Without starting a flame war, this is nonsense. It's a myth, and an incorrect one at that.

 

Just sounds like an old motor starting up to me. It's hard to guess on a youtube video but it does sound like lifter tick to me as well. 15w40 sounds good to me since you are in southern California. The thicker oil will take up some of the clearances in the engine. It won't cure anything, but it can create a little bit of a thicker barrier.

You could try an engine cleaner if you are worried there could be some sludge in the engine, and that could contribute to some engine noise. Especially if it's upper engine noise.

How is your warm oil pressure? In general worn rod bearings will cause an oil pressure drop when the engine is warm.

You can also rev the engine a little while in neutral (2k-3k maybe) and see what it sounds like as it coasts down. If it makes a rumbling sound it could be the rod bearings.

The bottom line is how far do you want to dive into the engine, and how much money do you want to spend on a 200k+ engine. If it is found to be rod bearings you can throw some of those in with the engine still in the truck. Not the most complete fix, but it might be the right price for an engine as old as yours.

 

ok well cold oil pressure is almost at 60 unless i give it alittle rev then it will go to 63. idle warm is around 36-42 after a 2 hour drive. never below 40 psi if its just a 10 mile drive which was the same as my sonoma. i listened to it yesterday and it sound like i have alittle knock lower on the driver side when warm + i believe alitle lifter tap. not to loud but im broke and this is guna kill my pockets / income. i would just like it to run like it is suppose to b4 it dies. this is not the original engine. i dont know how many miles are on this one.

 

If your warm oil pressure is that high then I doubt your mains are having issues, that is of course if your dash gauge is correct. If you wanted to check it further then you could use a manual gauge to check the pressure.

Here is how I look at the situation: You have an old high mileage truck. If it does indeed have an engine knock then there isn't really anything you can do right now to fix it. A thicker oil MAY prolong the life a little, but won't fix anything. If you don't have money to fix it anyway then my suggestion is just to drive it. if it blows you're looking at a new/rebuilt engine. If you fix it you are looking at a new/rebuilt engine. Same options just a different time frame. You just might not want to plan any trips to New York with it .

 

ok well the hotter the oil is the lower my pressure is but never hit 25 so im good there. knock is kinda fading away now at start up but my initial problem has come back. i was geting on the freeway, and the SES light came on, pep-boys read it to be lean bank 1/2 again damit. if im in drive and at a light it has some vibration and rms jump from 550 to about 650 and down again while the oil pressure gauge is having a siesure jumping all around from idle 35 to 40psi while im at the light but it just likes to jump with the rpm. at a light in neutral rpm is smooth at 650 and oil pressure is smooth at around 40.

 

You may have just had some junk in the upper end that is getting loosened up with some driving. As for the O2 sensor, can autozone check O2 sensor values with you or just check the code? If they can, check to make sure that all of the O2 sensors are switching values rapidly. If one is slow or stuck it's not doing it's job properly. Check the wiring too, if the wires have moved they could have burned on the exhaust. Check those things out first, it the O2 sensor checks out then you'll have to look elsewhere.

 

i will check that at my friends shop but autozone doesnt read codes any more, at least not in LA County, only pep-boys. what the o2 seconsor range suppose to be around?

 

It's not so much about the range of the O2 sensor, it's more important that it's active. They read from 0-1000 mv. I believe under 500 is lean and over 500 is rich. If you can check the values in real time in closed loop the readings should switch back and forth from rich to lean quickly. If you have one sensor reading fine and one sensor stuck in the 900's (or at any other value) for example it's probably gone lazy. If it's switching back and forth quickly you'll probably have to look elsewhere.

 

Yeah I found that out a week ago.

I was misinformed about it. Reinformed after I argued like an idiot with my oldest brother about it. He told me that it doesn't matter, you can switch to synthetic whenever you want without having to "break it in" first. Also found out that using the ac doesn't use any more fuel then if you don't use the ac. I dislike being misinformed lol