5-40 is the weight of a synthetic I use: I prefer Redline, and change it about every 12 months average.
The running pressure seems correct, and the idle might be a tad low, but normal to me. When everything is warmed up properly and you have been running the T, all dials are about in the 12oClock position. Don't fret if a bit lower or higher, it's the averages you pay attention. IF you are shwing it near touching either side, then we should talk more.
It is not unusual to have 348/T senders/sensors go south and those should be fixed and are basically easily replaced. Even the speedos sensor. However, having said that, I have a faulty sensor on a 456 dial and, phufff, I know enough about my car to feel the dial reading ;D -- you will too in time: don't panic.
I would be more inclined to watch a 'bouncing' dial indicator especially on the oil.
Make sure to check your fluids. Oil is always a 'different experience' for the new member of the dry-sump club, which your engine has.
- Get it to operating temperatures: about 20 min warmup is very decent...can even do this in your driveway but I like to be driving so, get out there.
- Pull over and
- Spring/open your engine hatch and leave in open/locked position
- Keep engine running: I, this is me, like to then pull out the dip, wipe clean and do a quick check of what's on the stick, then replace the stick in its hole.
- walk to the cockpit, turn off the engine, and within 1-20 seconds put the stick out and check the results. If fast enough you 'may' even do this a couple times < 30seconds.
IF below the low mark a notch add about 1/2-1 qt. I suggest 1/2, then do the above again.
IF between the two marks you are probably ok.
IF touching the upper mark then DO NOT add any more oil: Too much is not good. Matter of fact if above that mark, solidly, I would very consider draining some oil out. Overfill is not good, and this is where the dry-sump newbies panic and can make a mistake.
So, some tips.
1. don't panic
2. not unusual to add 1/2-1gt, sometimes, after only 500 miles, but honestly, that doesn't happen all the time. You may be fine for weeks then not. Depends on the types of run. Check after every longish period/miles of 500miles or greater. You'll get better when you get more familiar.
3. make sure to check ONLY when it has been brought to temp and not cold or when engine is idle for over a few min. You won't get the proper reading and it will look EMPTY. That's where newbies start adding 1-2 qts by mistake. They think it's dry and just slap a bunch of oil in there and then the oil enters into the engine and and well, it's not fun.
4. IF in doubt, about the level of oil....get it warm, and check it as per above.
When the oil level is getting a bit low, and you get more experience with your car, you will notice the nuance of how slightly poorly it will sound and feel. Trust me, drive it a lot and those small sounds, feels, etc. will be there and you'll start to suspect 'something feels off'. BUT, refer back to #1 = don't panic---hitch hiker's guide to the universe.
I seem to always know when the oil feels a bit low, when a tire starts to decline, and can hear, in open cockpit and engine running well on a freeway with all the noise, that 'sound' somewhere that wasn't there before....and then, I start to pay attention differently, but, typically not much more than the usual suspects.
IF your car was preped and ready for action [thinking it had its major done correctly and you are withing those guidelines] that there isn't much to worry about on the 348 engine: they are about a rock as one could expect.
Guide to the Galaxy: Don't Panic
Rik -- LAH !
1990 Mondial T Cabriolet SN 86247 : Red/Tan
1995 456 GT 2+2 SN 99987 : Roso Metalizzato [Fer 311/C] & Tan