I use amsoil in the diffs , and the engines of my other cars and bikes. Just not in the rover....I'm sticking with tried and true Rotella for this engine.

 

Amsoil makes some very good true PAO synthetic HDEOs (unlike "synthetic" mobil 1 or rotella) so if you got the money Amsoil 5w40 or 0w40 or 10w40 or 15w40 would be a better oil. You will not see that difference in 5k mile OCIs though.

 

Its not a perception of low idle, before this oil change it would idle in drive just above the 3rd mark and sound healthy, after the oil change (and for the last year of walmart oil) the needle sits about just over 16/th under the third mark and has a slight roughness similar to a plug misfire, almost sounding like it wants to stall....turning the heat on seems to make it sound a little more unstable.
i do have a bad plug wire, and the coolant was about a coke can low. Bad wire is not visibly arcing...(wire rested against valve cover and melted a bit...did a temp fix by covering that part of wire with high temp goo glue...works!)
i'll just change the oil again next week and post back with the result

 

Thanks for that info, Lipadj46...good stuff!

 

Again oil does not affect idle, something else is going on like your idle solenoid is dirty or dying or you have a vacuum leak or you need a tuneup etc.

 

To thin of a oil could cause more resistance inside the engine by not properly lubricating the moving parts inside the engine and thus increasing friction and making the engine work harder at idle.
But it still wouldnt make a noticeable difference to the driver.

And lets not forget that the tach is far from accurate.

 

well hows this for ya....
was waiting for the engine to warm up while while topping up coolant (another thread!)
i noticed the idle was unusually high (around 1200) so i unplugged the idle control valve, the rpms came down to "normal level" i then throttled the car once and then engine revved then started to die...then died...
i turned off the ignition, plugged the ICV back in then started the car again. now the idle is perfect, both in park and drive.
is the valve cleanable?

 

Yes, yes it is.
And it is recommended to be cleaned once a year to keep this running smooth.
Just make damn sure you do NOT move the plunger when you take it out to clean.
Spray with carb cleaner, clean the port it goes into also, put it back and go.

 

after cleaning the idle control valve the car is back to running at rough idle....time to replace i think

 

Thinner oil will not cause more friction at the same oil pressure. Thin oil lubricates as well as thick oil and actually with lower friction when oil pressures are equal. Where a thinner oil will break down is if the temps get too high and pressure drops off (due to thinning) or if the oil clearances have become too large and the pressure drops off.