Oil Gauge Fluxuation

Its normal for oil pressure to drop when idling. try using a synthetic and a

15w-40, I run 15-40 in my 4.3 in my S-10, have for the last 2 years, and I do it year round, oil pressure never drops below 40lbs and when idling and its extremely hot outside. Some might not like the idea of 15w-40, but it works great for me. I also run Schaeffers Supreme 7000, its also available in 5w-30. But the bad thing is it cost me $4.75 a quart.

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give it a shot

By the way, being the engine is started to get up in milage, I would stick with a thicker oil.

You got 150 thousand miles out of a 4.3L V-6? Wow! That's over twice the miles that I averaged on a typical 4.3L V-6. If you are the adventuresome type, you can retard the timing so that your truck won't ping on regular, but it will probably feel like you're pulling a trailer. I set my timing up so that the truck was optimized for premium gas.

Your story sure brings back memories. I had three different 4.3L V-6 motors in my 1990 Scottsdale. When I sold my truck, it had 219 thousand miles, so I was averaging around 73 thousand miles per 4.3L V-6. And yes, all of these motors had the widely-variable oil pressure that you describe and it was directly related to the motor RPM and/or idle speed.

My truck had a manual transmission and air conditioning. When the AC was on, I would get the huge fluctuations in oil pressure that you have described. The idle compensation for the air conditioning never worked properly, so at stops or during shifts, the engine RPM would drop and the oil pressure would go down to nearly nothing. With the AC on at stops, I would put the transmission in neutral and press down on the gas pedal enough to get the compressor operating properly and get the oil pressure up to 30 pounds. With the AC on during shifting, I would need to compensate for the drag of the AC compressor by goosing the gas pedal between shifts. Otherwise, the shifting would be very jerky.

My guess is that you have an automatic transmission and this would create extra drag on the engine when you are idling in the Drive position.

No, this type of engine speed/oil pressure fluctuation is not normal -- except for certain GM vehicles. After warming up to its normal operating temperature, my new 2004 Silverado (4.8L V-8 with 4-speed automatic) idles consistently at 500 RPM. It doesn't matter if the transmission is in Neutral or Drive and it doesn't matter if the AC is on or off. The oil pressure does vary slightly with engine speed, but it is nowhere near the extreme fluctuations that I experienced with my three beloved

4.3L V-6 motors.

I used 5W-30 during cold weather and 10W-30 during warm weather in all of my 4.3L V-6 motors. (On my 2004, I use the factory-recommended 5W-30 all year round.) I did notice that the oil pressure would be different with different weight oils. If I recall correctly, the lighter oil would give a higher oil pressure reading when cold, and when warm, both weights would be about the same.

I changed the oil and filter religiously every 2500 miles. I also did the tune up procedure twice as often as the factory recommended.

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Well a bit of dyslexia jumped in there. I have 105K miles on it. I am not sure as I would be as concerned if it were 150K

If I ever have to replace this motor, I will be doing a V8 crate motor swap. Got a fair amout of literature on what I need to do to do it, and it seems not much harder than a standard swap. Just a few extra dollars for the exhaust and whatnot.

Yep...automagic

Ok, so I am translating that as it is normal for your V6's (as you have had three), but not for the V8

Planning a swapover to Amsoil here in the very near future. I am impressed with the statistics of the product, ,and like the fact that all I have to do is change the filter at more regular intervals than the oil itself. I'm all about the 5 minute job so I can get on to something else, vice the 30 minute full on oil change.

my oil gauge does the same thing on all 3 of my chevy's. moves with the rpm's. on my 04 desiel 23,000,my 97 tahoe vortec 5.7 90,000. and my 95

350 z71 178,000. Have a Great One ! Bob :)

Eightup, perfectly normal.

Doc

Seems a lot of people have this problem. The dealership told me its normal and not to be alarmed, and my mechanic told me the same too. Idleing the engine obviously doesnt require as much oil pressure as opposed to driving down a free way or a road at 55-60 mph. I'm not concerned with my 4.3 in my

97 S-10, my dad also has an 4.3 Liter in a 95 GMC 3/4 Ton Vandura, his also does the same.

OK...cool. I trust ya Doc...I have been reading your posts for a while now. Actually I just changed the oil today. Pressure only fluxuated between 40 and 60, never below 40. I am happy with that!

I've never been concerned as long as an engine has had at least 15 psi with the engine idling and the transmission in drive.

If your vehicle only had idiot lights, you would be blissfully unaware of the fact that your engine oil pressure can drop to as low as 3 psi on some vehicles before the light comes on.

Put it this way, if the oil pressure DOESN'T change with engine RPM's, then it's time to worry! A healthy 4.3 V6, 5.0 or 5.7L V8 will idle between

15-30 psi HOT idle with the correct weight oil, and should run 40-60 psi at anything above 2500 RPM.

Doc

You just changed you oil? No wonder the oil pressure was up there, when you start driving it, it will drop as it warms up and thins out. When you change the oil, its fresh and cold compared to the used oil your taking out.

My new 2004 V6 Chevy van does that. Looks to be between around 20 PSI at idle when hot. It concerned me until a GM engineer on another board said it is due to the 5W30 oil. Apparently this 5w is recommended because of tighter clearances now in use. The manual says you *CAN* use 10W30 if temps do not go below 0, IIRC. What would concern me at low temps would be cold start lubrication with the 10W30. Apparently the low PSI when hot at idle are not an issue. Then again the dash gauges are notoriously inaccurate and there may well be more than 20 PSI. FWIW YMMV DFB

OK...I DID take it out on errands and get it hot before the report. Maybe I needed to be more clear. I guess common sense on my part is not the same as someone elses. But thanks for pointing that out.

Hey man, no one is perfect, I thought the same once too, then I stopped and thought for a min. Needless to say I am still thinking..........:-)

I have had 3 4.3's in 3 different gm trucks...they all bounced between

20 at idle and 60-70 at highway speeds...that is perfectly normal.

Ford explorers/rangers have a gauge needle, but it doesn't move....they had too many complaints about the needle moving, so they changed it to read in the middle unless it dropped below 5 psi.....what good does it do then?...might as well have an idiot light

yep

Sure enough. My most shining moment was when I did a tune up and forgot to put the rotor under the cap, and spent about 30 minutes tring to figure out why I had not spark. Luckily I tripped over the cap while walking aroung the car!

There is one engine that I will always have a love for, 5.7 Liter, I will always, and her little sister, the 4.3 liter. Engines are as tough as nails. I've even noticed my 350's oil pressure fluxuwates now and then too.

Ok, my spelling in this is terrible, its eairly and I am getting ready for work, so piss on it, I'm only running on 87 octane coffee, usually its strong (112)