Need help with oil pressure 87 tbi 350 with TH400 trans 4x4

[Matt Frediani]

Greetings.
I have an 87 V2500 GMC 4X4 3/4 ton with a TBI 350 / TH400 / NP 208
Truck is original one owner before me. speedo shows 93k. Motor runs great. I tested sending unit and it was bad. it showed low oil pressure so I changed it out with the correct delco unit. Now it shows 60psi at start up, when driving it shows about 50 psi on freeway. when its up to temp at idle it shows 45psi.

What oil should I use? I have Lukas Hot rod oil in it now that is 4qts of 10/40 and 1 qt of lukas oil stabilizer. truck is not driven much. I would like to keep it as original ass possible for as long as I can.

Should I be running Lukas 5-30 oil to lower the oil pressure? the oil pressure seems high to me? any help would be great! thanks!

 

[cstew47]

I have always been taught that oil pressure is like sex. You never get too much.

 

[Snoots]

Nah. You're good. When it gets colder, you being in Nor-Cal, going to a 5-30 may be better. As is it sounds like you have real good OP, nothing to be concerned with.

 

[Blue Ox]

Look in the manual. What does GM recommend?

 

[Grit dog]

What oil you use is far less important than proper maintenance, which I’m sure a beauty like that receives.
Save for zinc content, virtually anything you buy off the shelf today will be way better than whatever was reccomended in 1987.
Personally I use 15-W40 Dino diesel oil in virtually every 4 cycle engine I own. The only 2 that don’t are snow bike gets Rotella T6 5-w40 because it’s a winter time machine/wet clutch and Mustang GT Triton engine variety gets OW 20 syn as recommended. Because the Ferds have some very small oil galley passages somewhere in that engine that reportedly could partially starve components if high weight oil used.
Small blocks and big block Chevy motors, 6.4 Hemi SRT, 258 inline Jeep, mowers, diesel truck, all get 15W40 whatever is on sale when I need oil. And have for many years.
So that would be my recommendation

 

[JoeR Jr]

Greetings.
I have an 87 V2500 GMC 4X4 3/4 ton with a TBI 350 / TH400 / NP 208
Truck is original one owner before me. speedo shows 93k. Motor runs great. I tested sending unit and it was bad. it showed low oil pressure so I changed it out with the correct delco unit. Now it shows 60psi at start up, when driving it shows about 50 psi on freeway. when its up to temp at idle it shows 45psi.

What oil should I use? I have Lukas Hot rod oil in it now that is 4qts of 10/40 and 1 qt of lukas oil stabilizer. truck is not driven much. I would like to keep it as original ass possible for as long as I can.

Should I be running Lukas 5-30 oil to lower the oil pressure? the oil pressure seems high to me? any help would be great! thanks!

#1, As recommended already, it's not terribly important what weight oil you use. I'd run 10W30 with that oil pressure though. It's good pressure and providing plenty of lube and the lighter weight will help a little with the fuel mileage.
#2, Love that truck color scheme. Funny enough, I was working as a tech at a GMC dealer in those days. I ALMOST bought the same truck. We had one on the lot and I ended up buying a Monte Carlo SS instead.
Joe

 

[Rusty Nail]

pretty sure GM built it to run 5w-30.
I put conventional Valvoline in my truck.

it doesn't say on the oil cap?