Hey everyone. I just changed the oil last week with Royal Purple 10W-30. I used to use 5W-30 conventional with Lucas. I was camping for most of this past weekend (in 92 degree weather I might add) and I noticed when I was driving the car to pick up stuff from the nearby store, I would notice that after driving it for a few miles, the oil pressure would go down by about 10-12 PSI at idle and at speed. I would normally get 60 at startup and 40 at idle. After driving for a few miles, I would get just below 30 at idle and 45-50 at speed. I also drove 250 miles total roundtrip this weekend between where I was camping and where I go to college and noticed the same readings and I was driving ~65mph on the NYS Thruway. Is this normal for hot weather or am I noticing a warning sign of early failure? Should I grab the Lucas, take some of the oil out and put it in?

 

it could be a bad gauge, check the oil pressure with one that threads into the block and check it that way to see if the two gauges read the same

 

The figures you give are fairly common, so I would not worry about it.

 

Common for the 4.3 or common for hot weather?

 

For the 4.3 and perhaps some other engines. If you're seeing noticable differences in the pressure readings between hot and cold ambient temperatures, then I would say you have internal issues. As far as engine temp goes, as the oil heats up, of course you will see a pressure drop compared to a cold engine.

 

I mean I notice that in hot weather and sustained long distance high speed drives (120 miles)(especially when it is hot enough outside for me to use the A/C on full blast) I notice that drop, but not so much on shorter drives of only a few miles. I wasn't really noticing much of a drop after the oil change a couple weeks ago when it was around 40-50 degrees (maybe around a 5psi drop). This is with 10W-30 Royal Purple oil. It did almost the same thing with straight 5W-30 oil, but it seemed that with 5W-30 and the Lucas, it increased the oil pressures. Should I be looking into anything such as a small external oil cooler? I am trying to make this engine last at least 300k with minimal repairs if possible.
If it matters, the temp gauge ALWAYS stays just below 210 once the engine is fully warmed up, even when it is 95 degrees out. I just had the coolant flushed also since there was some mud in it, but the radiator guy said it was not oil or anything else to be worried about. Does this mean I need to use higher viscosity oil if I do not use Lucas? Thanks

 

I'll put it this way - mine shows ~40psi at idle and ~55psi at cruise. The old 'rule of thumb' is that you need 10 psi for each 1k rpm you're showing. Living where you do, 5W30 should be fine year-round.
If you really want to get into info about motor oil try bobistheoilguy.

 

Maybe it was because it was hot. I am back in the college town I live in and I am not seeing the pressure decreases I was seeing last weekend in the hot weather and high speeds. It is holding well at 38-42 at idle. 60-65 at 40-55 mph