89 S-10 Blazer: 4.3LV6: oil pressure question

have made the following observations lately on the vehicle in question. These pressures and observations are made before and after an oil change, and are the same:
cold idle pressure: approx 70PSI <gauge is the stock Chevy graduated bar, so this is an estimate based on the markings on the gauge> cold cruise pressure: approx same warm idle pressure: 15-20PSI warm cruise pressure: approx 40-50PSI. this is true if the throttle is pressed at all off of idle <ie: if I'm sitting at a light and barely tap the gas slowly, the pressure shoots straight to 40ishPSI>.
Idle pressures are with car in gear. If I put the car in park, while warm, pressure raises probably 5-10PSI <I know I need a mechanical oil pressure gauge for better troubleshooting, just don't have one>
Also-- if I nail the throttle while cruising, the oil pressure fluctuates between about 35-60PSIm, rapidly, and then stabilizes.
Oil is Castrol Syntec 10W30. I live in Charleston SC <subtropical climate>. Should I change to a different weight? Given that pressure comes up when revs do, I don't think I have a problem here-- but want to ask people who kow more than I do. For comparison, my 1990 Jeep Cherokee with the 4.0 straight six with over 2000,000 miles on it, using same oil, has rock-solid 40+PSI indicated at hot idle, and 60-70 at cold idle.
After this concern is addressed, I'm going to a bypass filter for my transmmission and oil filtration. See it here: http://www.bypassfilter.com/ . I am not affiliated with the product or sales, just VERY impressed with what I've seen from several friends who're running these. It's a GREAT way to save money, save wear, save the environment <not that I'm a treehugger>, and reduce our dependance on foreign oil.
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There is no way to do an analytical comparison with using a known accurate mechanical gage.

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sure there is.
Anyone got the same engine? See the same results?
I'm not looking for Oil Analysis by Proxy, here- just "hey, is this what you've been seeing in your vehicle" sorrt of bit.
Anyone got useful input?
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Have a 91 S-10 4.3 L.and my pressure is maxed out all the time. (guage reads 0-40-80) The only time I've ever seen it get under 40 PSI was after driving about 600 miles on the Interstate, took an offramp and then onto city streets with the old engine using 5W-30
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So your estimated readings on a un verified dash gage and sending unit are some how supposed to be compared to "what"?

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ok, I get it. You don't like the comparison.
Noted. move along till you have useful input, please? :)
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Those don't sound out of line for tolerance on the Crappy Chevy Gauge (CCG). My 88 S-10 with 4.3 has a new motor 25ish K ago, and is only slightly higher than that with Mobil 1 5W30.
Big Chris
snipped-for-privacy@gmail.com wrote:

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Thanks Chris-- this is what I'm talking about. ;)
I've got about the same mileage on this engine. I'm doing my final flush before going to Amsoil Synthetic 0w30 lube. I'll be using a motorguard bypass filter, preoiler worked into the start sequence, and oil analysis.
Once I drain this thing and go withthe above, I think I've pretty much seen my last oil change. ;)
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