1992 Isuzu 3.2 DOHC oil/hot issues. Oil recommendations?

Any 15w40 or 5w40 is a good start.
Use a Napa Platinum or Wix XP.

Mobil1 15w50 is another option.

You should pull the pan and/or valve covers and inspect for sludge.
 
I used a 20-50 as it was the thickest recommended in the owner’s manual. I may try a 5-40 in the winter as we are at the tail end of cold in my state. I pull my boat and motorcycles with this, engine temp never gets on warm side but oil seemed to thin on hot days and the valve train would rattle.

I will report back with results.
 
Ok, flame on, I went with this. Valvoline VR1 racing/high zinc 20-50, I think it’s dino not syn but I liked that it had higher zinc. It fired right up and ran smooth w/ ~60 psi oil. I took it out on the freeway after warmup and ran it hard in top gear to build up heat, then would downshift into 4th and hold it to 5k rpm. Ran like a champ, now that it has heat I took the off-ramp and let it fall to idle in town ~15 psi this is where it would usually rattle like diesel on the valvetrain and show barely single digits on pressure. nothing, no noise at all. Super quiet. I hope this keeps up when it gets above 80° here and I pull my boat with it.

Very promising so far. I’ll run this for 5k or so then do synthetic version of the same oil.

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Ok, flame on, I went with this. Valvoline VR1 racing/high zinc 20-50, I think it’s dino not syn but I liked that it had higher zinc. It fired right up and ran smooth w/ ~60 psi oil. I took it out on the freeway after warmup and ran it hard in top gear to build up heat, then would downshift into 4th and hold it to 5k rpm. Ran like a champ, now that it has heat I took the off-ramp and let it fall to idle in town ~15 psi this is where it would usually rattle like diesel on the valvetrain and show barely single digits on pressure. nothing, no noise at all. Super quiet. I hope this keeps up when it gets above 80° here and I pull my boat with it.

Very promising so far. I’ll run this for 5k or so then do synthetic version of the same oil.

View attachment 145137View attachment 145138
I think that is Valvoline's version of Castrol GTX Classic.
 
Just checking in, still runs quite even on warm days. Hoping no more issues, fixing AC now, compressor froze up. I’ll have more money in this than I paid for it, sigh, but still cheaper/better than a new truck. $35k for a Chevy Colorado? ***? The world is insane now.
 
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I don't know why there is a constant infatuation or usage of conventional VR1.

Went to walmart.... Conventional VR1 quart was $8.50. Synthetic Mobil1 15w50 was $8/qt. Conventional VR1 was $10 more for a 5 quart jug when compared to synthetic Mobil1 15w50 jug.

I see ever thread on every forum mentioning vr1 as a joke. Blind sheep!
 
Well, I wouldn't go so far as to call people sheep, but I agree it's nothing special and not needed.

Personally, I would put lower cost 10w-40 or 15w-40 in it and expect the same good results.
 
I don't know why there is a constant infatuation or usage of conventional VR1.

Went to walmart.... Conventional VR1 quart was $8.50. Synthetic Mobil1 15w50 was $8/qt. Conventional VR1 was $10 more for a 5 quart jug when compared to synthetic Mobil1 15w50 jug.

I see ever thread on every forum mentioning vr1 as a joke. Blind sheep!
I bought it because it was the only one on the shelf in the weight I wanted. But thanks for puffing up and pounding your chest trying to virtue signal. 👍
 
IMO you have a failing bypass and/or oil pump.
Back in the day I had a 95 Rodeo with the same 3.2l engine that I bought with < 70k miles. It had the same oil pressure that the OP reports and the last I knew, it lasted to 240k when the family member I gave it to sold if off. It lived on a diet of Delo 400 or Delvac 15w-40.

Edit: When I said "a diet of", I meant exactly that as it would consume a quart of oil in just under a thousand miles from the time I bought it.
 
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Those are pretty notorious for spinning a bearing if run even moderately low on oil, and they also are know to be oil burners with some frequency.... not the best combination.

By any chance have you checked the oil level right right after the oil pressure dropped?
 
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