From a cold start (first fire up in the morning), the Blazer Oil pressure goes from 0 to about 60 psi (at idle). At run temperature (temp guage sitting at approx. 170 degrees) the Oil Pressure runs at about 40 psi. At acceleration, the Oil Pressure will drop to about 20 psi briefly then return back up to about 40 psi.
The oil has been changed regularly, since I bought it (3 years ago). I'm using 5W-30. The oil is jet black (no milkshakes here). She idles smoothly, runs strong, and there are no leaks. There is no blue smoke and the oil level is always within the proper capacity range when checked (cold).
Is it normal for the Oil Pressure guage to "fluctuate" like it does or is this a possible harbinger of a failing oil pressure sending unit? Any thoughts? Thanks for the input.
NOTE: all pressures are approximate based on eyeball to guage readings.

 

Fluctuations and running 40-60 psi are both perfectly normal. I think it is a little strange that upon acceleration the pressure dips to ~20 psi momentarily, but I wouldn't be concerned about it. You're good down to ~6 psi at idle. The old rule of thumb is 10 psi per 1,000 rpm.

 

Not too mention the oil being "jet black". When was the last time the oil was changed? Is the oil level full? How old is the oil filter?

 

I would change the oil, cause the oil should be a nicer light brown color. Also while your at it replace the oil filter. As for the psi mine runs between 40 and 60psi, most of the time 60psi especially when accelerating. When it warms up and is just idling (like at a light) it sits about 40 psi or a little higher, never did that till recently but I think it is cause we finally have some warm weather and I switched to a synthetic blend.

-Lenny

 

Actually, color is not a very good indication of when to change the oil. If oil is holding dirt or other particles in suspension, it's doing what it is supposed to do. Some oils will turn dark sooner than other oils will (sometimes within 1,000 miles).
Junkmonkey, what brand of oil are you using and what type of oil change intervals are you running?

 

I generally run oil changes at about 3000 to 3500 miles, and I always change the filter at the same time. Because of the frequent oil changes I use whatever is on sale, so the brand may change. Of course I recognize that the oil is "cheap" and it'll turn black in a short time frame (thus my reference to jet black oil, color noted upon removal from the pan) but considering the short intervals between oil and filter changes I can't justify putting in expensive oil, only to be throwing it away (recycled, of course) a couple months later. I remember back in the day when my Dad change the oil in the ol' Pontiac every 10,000 miles and that beast ran forever and a day. Was oil any better back then, than it is today? I doubt it.

Based upon the input so far, it sounds like the Blazer is A OK (as far as oil pressure goes). I have / had no major complaints with this vehicle. She's been good to me since I got her and I keep her running as well as I can for my 16 year old son who has claimed her as his own. Now, if I could only get him to change the oil.....or at least to show a modicum of interest in getting his hands dirty I'd be a happy man.....sighhhhhh!

 

Sounds like a plan.

 

If you don't beat the **** out of the truck, when running a good synthetic, you can do 7 - 10 thousand miles on one oil change, easy!

maybe throw in just a filter change at 3 - 4 thousand...