At idle, my oil pressure is just over 30psi
In gears 1-4, the oil pressure will rise to about 60psi at just under 2500rpms
So thats normal.

But in 5th gear going about 85-90mph, the oil pressure will drop to maybe 50psi or so. And if I floor it to full boost it'll drop even more than that. What could be the problem?


Its an 87' Turbo II. I was running 10w-40 royal purple. Just changed to 20w-50 today and it helped, but it still drops a bit, though not as much.

Thanks in advance
Jon