Change Oil light- Condition not mileage- accurate?

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Orlando, FL
'95 Caprice lt1 57k

Quick background: car was neglected. Sludge/carbon/varnish. All pics can be seen clicking on the link below. Currently on first OCI since purchasing the car. Full background can be seen here-
https://bobistheoilguy.com/forums/ubbthr...flu#Post4208603

793 miles into the OCI, the Change Oil light came on. I checked the owners manual and to my surprise, the light comes on by determining the condition of the oil instead of by the mileage.


Car is currently on 4 qts of Havoline dino and .5 qt of PP. Well really a total of 4.5qts. I'll explain: these cars normally take a total of 5 qts. This one however only took 4.5qts to get the dipstick to full. I'm assuming because there's about an equivalent of .5 qts of sludge laying around inside and on the oil pan.

How accurate can this determination be? Especially from a '95 vehicle. Maybe I have Blackstone Labs at my finger tips haha.
 
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The system worked very well in my Chevy HHR. Now if they had only installed a proper timing chain tensioner:( You probably did not reset the monitor when you changed the oil.
 
Yes, GM began gradually phasing in their OLM in the late 80s or early 90s, and almost every GM car since 2000 has it. What were your driving conditions during the OCI? How long did it take you to put on the 793 miles? The newer OLM algorithms are even more sophisticated, taking into account coolant temp, oil temp, ambient temp, oil pressure, rpm, cold starts, idle time, and possibly more.

Remember that the SG/SH oil from the mid-90s is nowhere near the performance of today's modern SN/dexos oil, and synthetic was nowhere near as popular as it is today (for example, SH allowed 25% NOACK, compared to 15 with SN, and 13 with dexos). Therefore, factory OCI's were shorter back then, and that includes OLM-calculated intervals. Back then, they mainly had Group I, whereas even the cheapest SN has some synthetic in it (cheap Smitty's at Kmart is 10% PAO, and most SN "dino" has some group III in it)
 
You should add some MMO towards the end of the OCI.
wink.gif
 
It doesn't test the oil directly. I cant see sludge, it doesn't know what oil you put in it. It uses a bunch of engine parameters to determine when to change. Unless the car was idled for the whole time or lots 2 min trips. I have never seen a OLM go off in that amount of miles unless it was for time. I would say the OLM was not reset. I have had more than one car in my career where I thought I had reset the OLM and had not and 4 wks later the light comes on. The newer stuff isn't as big issue because you can the OLM in a percentage instead of just waiting for the light.
 
What does the color of the oil look like? I was would just reset the oil light and run it for your OCI.

When you change the oil take a look to see if any of that sludge was cleaned up.
 
793mi. 70/30. That 30% is parking lot not moving rush hour traffic being on the highway and hour and half to move 6mi. Oil is getting pretty dark already. Could it be that .5 wts of PP cleaning?!
 
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My '99 Chevy 5.7L OLM has come on twice since I owned the car - a total of approx 6,000 miles in 5 years. I don't think this vintage is particularly smart. I think it's just 3,000 miles. All my trips are 14-25 miles long on average. I get to operating coolant temp within 3-5 minutes. The car is never idled for more than a couple minutes. Basically once it starts, I drive it continuously at 1,600-4,000 rpm. There's no way the oil is spent at 3,000 miles. In any case, I change it annually which is only 1200 miles. No need for an OLM.
 
Originally Posted By: gallydif

I checked the owners manual and to my surprise, the light comes on by determining the condition of the oil instead of by the mileage.


Thats not what it says. It says it determines the condition of your oil based on driving habits and conditions, engine speed, temperature, vehicles speed, etc. It is not doing an oil analysis. I suspect you didn't reset it when you changed it.
 
That's certainly possible. One has to make sure the pedal dance, as noted on the bottom of the manual page in the original post, is done correctly. I've goofed it up myself over the years.
 
Originally Posted By: gallydif
Oil is getting pretty dark already. Could it be that .5 wts of PP cleaning?!

Yes, that's exactly what it is! That half quart of Pennzoil Platinum Internal Engine Degreaser, Brake Parts Cleaning Solvent, and also Motor Oil© has cleaned so much sludge that the computer is telling you to replace it before it starts eating the iron block. Pennzoil Platinum is really that effective! Next time use only a quarter quart and you may make it to 1k before the oil light comes on. Powerful stuff!
 
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