Which weight oil should I use for my 3.4?

[sx460]

I've got a '95 Lumina with a 3.4. It says to use 5w-30 but the car has 120,000 miles on it. I've got a friend with a '85 Mustang GT (5.0, carburated). His car is "supposed" to use 5w-30. He always ran either 10w-30 or 10w-40. I talked him into using what the car says it should use (5w-30) and with the thinner weight oil he gets a constant valve tap. He explains it that the oil is too thin and it passes through the clearances faster than a thicker weight oil would, and so it isn't doing as good of a job as a thicker oil.

 

What do you guys suggest for oil weight on my 3.4? BTW: I do get a constant noise from my motor, but not sure what it is. Could be a vacuum leak or something. Either way, just thinking that a thicker oil might not be a bad idea for a 7 year old car with 120,000+ miles on it.

[dykz34]

5W-30.

[NORBI]

I will not say DONT USE Synthetic old but i used it once on my 94 CS with 3.4 DOHC and car started to burn a lot of oil and it only had 57k miles and when i stoped it didnt burn anymore oil. I say use 10W 30 thats what i used after that and never had any problems but i even used a 10W 40 and didnt nottice any difference so i say its safe to use both.

[sx460]

Thanks for your suggestions guys. I guess if it doesn't hurt I'll just try a thicker oil after winter and see how it works. I've always used synthetic and so I don't know what it's like without it. I've often considered just using a decent quality blend/dino oil (but also in a thicker weight). My car is always 1 quart lower in oil when I change the oil. So maybe dino oil won't burn as much.

[STR]

5w30