Hello all, I have a'96 classic 4.0 with 138,000 miles, my mechanic was putting in 5-w30 oil in the winter, so I'm guessing that being we got our first real heat here in NY 85-90 degrees, i should bump it up to 10-w30? Here's what's happening, when it was 90 degrees, I was local driving for about 45 min and noticed that when I come to a stop, the OP drops to 20, should I be concerned? Or could thus be a sending unit problem? I will be taking her on the beach so I just want to make sure this isn't a major problem. Thank you

 

5-30 is fine and 20# at hot idle is also fine. Minimum spec is 13# hot idle and you are well above that.
5-30 and 10-30 are the same viscosity at operating temp.(30wt) They are different only when cold.

 

Ok great! TY

 

x2 you're fine. Quick check:

- Can you see oil on the cylinder head if you pop off the oil filler cap with the engine running? It may or may not splash at you
- Is your engine making knocking noises? Liter tap doesn't count

Should be "yes" and "no"

 

Life was alot easier when all we had was an idiot light!

 

Hence manufacturers turning gauges back into the equivalent of idiot lights. Either they read normal, or they do not. When the gauges actually move the average owner gets worried.

 

Mine makes a knock at idle... I rev it up and it goes away.

Oil pressure reads 10psi when its hot. (I have not verified the gauge accuracy or cleaned the sender elbow)

But its the knock/tap that I worry about..

 

Yeah you might want to look into that. Follow some of the tips on here about verifying the sending unit and cleaning gunk out. And if you have a FRAM filter... toss it

 

First thing I did was change the oil and put a WIX filter on there.

I'm going to put my ScanGage II on there and see what oil pressure it reads.

 

Whatever is causing the knock is probably what is causing the low oil pressure. Welcome to the club of 2000 4.0s with low oil pressure, a common problem with that year. There are a number of reasons, the most often blamed is the cracked head scenario BUT this year also has a history of blown head gaskets and wrong cam bearings. If you are not losing coolant you can out rule the cracked head and gasket. I have the same issue (less than 7 psi) and a slight knock at idle which is most likely lifter noise. Since your noise goes away with an increase in rpm it is probably a leaky lifter that can't keep up with the low amount of oil it is getting at idle. Mine has been doing this for a long time and I really don't worry about it.

 

Thanks for sharing... now I'm not so paranoid. My oil looks clean and I'm not seeing any coolant loss either. I'm just gonna run it, and try to keep it cool.

 

You said that you mechanic did your oil change for you. What brand of oil filter did he put on? Like salad said if he put a fram or any other off brand get rid of it and replace it with a Mopar, Wix or Napa Gold filter. A crappy filter can give you a lower oil pressure reading.

 

+1
I got a noticable increase in oil pressure (7-8LBS) going from Fram to NAPA Gold (WIX supposedly).
I'm getting ready to do an oil and filter change soon and been reading on various sites about how the 4.0's do well with Rotella brand oil. Especially T6 5w40. My motor has always done well with NAPA 10w30 std oil. Even in our coldest weather I get no noise at start up ('96 w/136,000) so I may go with Rotella's 10w30 std or blend.

 

i run the rotella tb 1030 synthetic blend with a mopar or wix filter at 5000 mile change intervals

 

I'm going to try the Rotella 10w30 blend next change too... lots of good things I've heard..