Mod = oil pressure change = switch viscosity?

[CaveatLector]

Question: Should I change to a different weight/viscosity synthetic oil as a result of a modification and resulting change in oil pressure?

1997 Chevy Astro 4.3 V6
170,000 miles
5w30 as GM Manual states (Mobil1)
Car Quest (Wix/Napa Gold) oil filter
location: Texas

I did the "oil cooler delete" on my 1997 Chevy Astro 4.3 V6. I removed the oil cooler lines, and the adapter from between the oil filter and engine block. Now my filter mounts directly to the engine block. I am very happy with this modification but my oil pressure gauge reading did change a bit.

Most people report a DECREASE in oil pressure as a result of doing this mod on a 4.3 V6. My oil pressure stayed the same or INCREASED, which is odd. Here are readings from my stock oil pressure gauge, the first number is psi with oil cooler, the second number is psi with no oil cooler: (oil gauge dial goes up to 80 psi)

at cold start: 40 / 60
parked, hot & idling: 17.5 / 17.5
parked, hot & rev'd up: 42.5 / 55
hot, cruising at 50mph: 30 / 35

I am not sure if the block or oil filter's bypass valves are opening at cold start and 60 psi and redirecting that thicker oil back into the oil pan. Not sure if the engine block bypass valve redirects oil back into the pan or through the engine to lube the engine. Since the delete, my oil gauge needle is much more responsive to changes in engine rpm.

I'm wondering if I should switch from the 5w30 as stated in my Astro manual to a different oil, maybe 0w30 to get that initial oil pressure down to what it was at cold start. I imagine there is less restriction now with the oil lines gone, which is why my psi went up so my oil filter must be getting more psi than designed and as a result my bypass valve(s) in the filter or engine block might be opening up too soon.

Thanks for any comments.

 

[beast3300]

No need to change anything. Your pressures are fine. GM specs 5w30 for 4.3 without oil cooler as well.

 

[CaveatLector]

Yes the non-oil-cooler Astros had the same 5w30 spec but I think they also had different oil pressure settings to account for the lack of oil cooler.

 

[45ACP]

Cool. But why would you want to do an "oil cooler delete?"

Let me guess.. does the oil temp being hotter make the engine run better?

Had the Vin "W" in a 1994 S-10. COOLANT temp would get to 240 degrees in traffic stop-and-go with the AC on. Anything over that and the AC had to get turned off for a bit. Now, i know the fan kicks on at 220, but would 40-weight oil help that? Or was 3-wt oil OK there. Had the digital instrument cluster and when it worked it was great. Had OP readings too, pretty sure (had 4 squares and then the main part. Batt, Gas, OP, coolant temp.) Also RPM and speedo of ocurse.

That motor is AWESOME.

Now, advice to oil as to temps i listed? And "Is that normal for that car." Was told by dealer it was, likes to run hot but as long as it does not get over 240 its ok.

 

[CaveatLector]

I don't tow, rarely use ac, drive conservatively, always use full synthetic oil with new filter. I just don't need the oil cooler function. The oil lines always end up leaking because GM insisted on using aluminum crimps and weak "paper clip" retention wires for the fittings. 3 fluid radiators tend to leak and mix fluids. Less parts, less in the way, less to break down or leave me with a blown out oil line and destroyed engine. In my opinion my van is MORE reliable now without the oil cooler stuff. If I ever need an oil cooler I will add an aftermarket external unit. It also makes it easier to work on the van without the oil stuff there. Astro vans are already cramped on space in there... coolant draining was a breeze without those lines there last week lol...