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06 DTS, 97 Eldorado Convertible
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Discussion Starter #1
Hello! I recently spent a long time trying to address the low oil pressure light at a hot idle, and figured I’d write a post sharing the solution.

On my stock ETC with 55k miles, the oil light would flicker and eventually stay on as the oil got hot, yet there were no unusual noises or anything along those lines. I went through the forums and tried all of the usual trouble spots - replaced the pressure switch/sender with a new AC Delco unit, re-torqued the balanced bolt, and changed the oil (10W-30 conventional). No luck. I did the overfill procedure, which didn’t resolve the issue. A mechanical gauge showed that my oil pressure was borderline adequate at idle, perhaps just a tad low.

Well, that slightly low oil pressure at idle was enough to trip the light. I called Northstar Performance, and was told that he has noticed a batch of 97 engines that can’t quite seem to keep the oil pressure up to par with the rest of them - and unfortunately there is no known solution. With 10W-30, they are about 1 psi too low at idle. I changed my oil to Shell Rotella 15W-40 (it is a summer car, not worried about the high cold rating) and that did the trick!
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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70,723 Posts
Regardless of a slightly low oil pressure at idle, using a 15W-40 or HD commercial diesel engine oil weight is NOT recommended due to the Northstar tight bearing clearances. Summer or not, Arabia or Mojave.

Oil flow is lubrication and cooling; pressure is bearing/passage flow restriction. 5 - 15 psi at idle, hot, is just fine. When you did the gauge test what was the hot pressure at 2,000 rpm? 45 - 55 ??

Use the 10W-30 as recommended by GM/Cadillac. Your pre-2000 flat tappet engine might like a so-called "high mileage" oil.
 

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2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
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1,860 Posts
Interesting comments on '97s.

I too had a '97 STS with the hot oil idle issue. Get it just off idle and the light went out.
I figured that the pressure was just below the threshold for the switch, but enough for lube at idle....just that creepy red light and ding, ding, ding of the chime was unsettling.
 

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06 DTS, 97 Eldorado Convertible
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10 Posts
Discussion Starter #5
I know it isn’t the factory spec oil, but being that there is no known solution, this is the best option in my opinion. Obviously a later engine would be an improvement, but I don’t feel like that is worth the expense. I also value its originality, as a dealer-ordered coach builder’s convertible.
 
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