Cadillac 4.6L Northstar "Check Engine Oil" message when only 1/2 quart low!

I have been helping my neighbors with several cars. One was in poor health and wasn’t able to fully maintain the vehicles anymore. One includes a Cadillac Northstar 4.6L that was long overdue for an oil change. They had been adding oil but it was burning quite a bit. It was going through a quart every 200 miles or so! There were no leaks and no smoke from the engine which was surprising to me. I did some research and understand that this engine will stick rings if not driven hard once a week or so and/or isn’t maintained well. I am pretty sure the oil was something cheap from Wal-Mart and the filter was the basic Fram which appeared much smaller than the replacement. The oil was coal-tar black and two quarts low when I changed it for them.

Anyway, I put an AC Delco filter and a fresh fill of Mobil 1 0W40 European Spec oil in the car. I then took the car out and ran it HARD in second gear. The engine was running MUCH better with a lot less lifter noise and just sounded smoother all around. The oil usage also dropped but hasn’t stopped. The new oil turned coal-tar black within a 1000 miles or so. I told her it was time for an oil change again but could wait for another 300 mile trip.

I know several people, myself included, who run this oil in all their vehicles calling for 5W30. The ACEA specs endorsed by VW, Audi, Mercedes, BMW, and such are more stringent than what we have in the U.S. Oils meeting this specification tend to clean sludge and other engine deposits to a greater degree and allow for extended change intervals (with appropriate filter) specified by the European manufacturers. I also understand that this is a “thin” 40 weight by spec. It is more like a 0W35 from what I understand.

She has had this oil in her car for 1000 miles or so and then takes one last trip before I told her I would change it again. I have added a couple quarts since the change and made sure the oil was at the FULL mark before she left. She made it to her destination without incident. Soon after leaving her “Check Engine Oil” message lit up. She stopped at an AutoZone where an employee checked her oil and noted it was 1/2 quart low. She purchased a quart, added some, and continued on.

I am curious as to why she would have been 2 quarts low in the past and not had this. I have checked her oil and added an entire quart and this light was never on. I am wondering if this new oil dissolved deposits and crap in the engine from the neglected prior change. This would explain why the oil turned black so fast. I am wondering if her filter began to plug with gunk. Either way, we have a filter and oil on hand and are planning to do a change. I told her we need to do this ASAP! Does the sensor measure oil pressure or oil level? If pressure, crap could be clogging the filter or oil pump pickup screen.

Any other thoughts?

The “check engine oil” light comes on when the oil level sensor indicates the engine oil level is low. This sensor screws into the side of the oil pan. It’s a simple float device and if the engine is particularly sludged up could have been sticking in the past or now.

You’re a handy guy. Next time you change the oil, replace the sensor. The sensor just screws out of the oil pan (facing the front of the car) and you’ll have to twist and jiggle it just right to replace it.

You’re on the right track about engine oils. So many people grab a jug of whatever brand 5W30 is on sale and then wonder why their Audi or Mercedes engine only lasted 80,000 miles.

1/2 quart low normally wouldn’t trigger a CEL, whether the sensor involved measured pressure or level. I expect this is an oil pressure problem. It might just be the oil pressure sensor has failed. A mechanic could use a shop oil pressure guage, plug it in whre the existing oil pressure sensor resides, to independently confirm the oil pressure reading.

Is this new oil a synthetic? I’ve heard that if a synthetic is used on a car that has routinely used normal oil, problems like this can occur. The synthetics apparenently have better cleaning ability, and may dissolve existing deposits inside the engine. You’d think this would be a good thing, but there are downsides, like resulting oil leaks and plugged up oil filters. In any event, I agree w/you this needs to be addressed asap. You should also check with the dealership to verify the type of oil you are using meets the Cadillac specs for this make/model/year.

Well I’ve got the 4.0 Northstar and there is no way that 0-40 is the proper oil. Check the manual but I’m sure its going to spec 10-30 in the summer and 5-30 in the winter. 0 is too thin and 40 is too thick. There also is no need to use synthetic, especially if it is not well cared for and needs more frequent changes.

The oil level monitor is in the pan so I suppose it is possible that the thick oil was not draining back down fast enough and triggered the sensor. Not really worth pursuing though in my view.

NorthStars don’t tolerate neglect very well…If the oil was allowed to degrade into tar, the damage has been done…Switching to expensive European spec synthetic oil isn’t going to repair the damage. If the fresh oil turns black quickly, the engine is badly sludged. Good luck with that one…

I had her bring the new oil and filter down tonight when she got home and I decided to look into the situation. The good news is that the message said “Change Engine Oil” and NOT “Check Engine Oil”. I went ahead and changed the oil. Although the old oil was definitely black and ready to be changed, it wasn’t sludgy like other oils I have seen drain out. I reset the notification and all is well. She called me in a panic from AutoZone and I posted this before she was even back.

As for the performance oil, this is a performance engine designed to compete with BMW, Mercedes, Lexus, and the like. The manual for the 4.6L specs 5W30 all year and 10W30 in the summer only if 5W30 isn’t available. They also don’t require synthetic.

As for the 0W40, I got onto this as I have a Geo Metro for the 52-55 mpg I routinely get. These use a high revving 1.0L 3 cylinder engine which specs 5W30 from the factory. Of course these were a cheap car when new and many people weren’t really good about maintaining them. The general consensus on the forums seems to be that the synthetics, especially the Euro spec stuff, is a godsend for these engines. Their high revving nature is hard on oil and leads to sludging and stuck rings if neglected much at all. People routinely use 0W30, 0W40, 5W30, and 5W40 full synthetics in these engines with excellent results. There are even a few using 0W20 although I wouldn’t do that.

As for oil weights, the 0W means that the oil behaves as a 0 weight oil when cold and a 40 weight oil when hot (210 F). The oil thins as it warms so it is no thinner than the 40W when hot, plus you get faster lubrication when cold. If this was a conventional oil, I wouldn’t even THINK about using something like this in an engine unless specified. In this case, a lower cold number won’t hurt a thing. I was nervous about the 40W at first too but have been told they essentially cheated on the rating and that this is a very thin 40W. Either way, I know lots of people who use this oil in engines calling for 5W30 and 10W30 without any issues and they run forever. You can get the Euro spec oils in other grades and brands but for some reason this is all the parts stores and Wal-Mart seem to carry in the small town where I live. You can’t go wrong getting this for $22.50 per 5 quart jug at Wal-Mart. This isn’t much more than the cheapest dino oil!

All in all, I am glad this notification wasn’t a sign of something worse. I will remember the sensor in case it ever acts up.

I’m all for using synthetic oil, but what I would do with this particular car is:
-Pour in a can of engine flush or Seafoam and let the motor idle for about 20 minutes.
-Change the oil and filter with whatever name brand 10W30 dino oil is on sale. Run it about 500/1000 miles and change the oil and filter again, this time with synthetic if you want.

Mobil-1 is good oil, but I’ve been using Amsoil lately. I used to get about a quart of consumption between 5K oil changes with Mobil-1. With Amsoil, my engine uses no oil between changes.

Ah, oil wars. All cars can benefit from improved cold oil startups. All cold oil flows poorly. A motor spec’d for 5-30 can benefit from using 0-30. It is the hot spec that is most important. If owners manual sez use xx-30 than use 30. Using 40 weight is not good. Higher viscosity means less flow.

+1 for @Bing. You are using the wrong oil.

Ok, I will switch is back to a 0 or 5W30 on the next change. I think sticking with synthetic is the way to go as several of the issues this engine had either went away or improved during this last change. I wish I could find another Euro spec oil for a similar price. All are nearly double or more the Mobil 1.

Looks like it was all just a tempest in a teapot, just the ECM saying time for an oil change. I wonder how it decides? Just by the number of miles since the last one – providing it somehow knows when the oil is changed --or it might have a clarity sensor and if the oil gets too brown it triggers that message.

There must be a lot of funny stories about drivers who misunderstand what’s happening w/their cars. I was driving a rental car out in the desert, stopped for break, then got back in and couldn’t shift out of Park. I tried and tried, no go. Eventually I saw a big notice on the dash “If you can’t shift out of Park, try pushing on the brake pedal first!”. lol … My Corolla is a manual xmission so I’d never encountered the brake safety lock used on automatics. I thought I was destined to die of thirst in the desert. And another time I had a relative w/a SUV that had two gas tanks, and she called one day saying “Oh no, I ran out of gas”, but when I got there to help I discovered all she had to do was switch the tank selection lever to the other tank, which was full to the brim!

It doesn’t know when you change oil. You have to reset the oil life indicator and it starts its computations over again. If its not re-set, it thinks it hasn’t been changed. Just based on time, mileage, and start-ups is all.

My 89 Mustang GT 5.0 will trip the “check” low level oil light when it drops to 3/4 of a quart low…a nice thing to have if you forget to check the oil level between oil changes. When the light comes on shows nothing on the stick…add a quart and measures just over the full mark. 112k and loses some due to valve cover gasket seepage…about half of quart every 2500 miles…cheaper to add oil then having to remove the throttle body to get the valve covers off…Been like this for 15 years now…Change oil every 6 months using 15W-40 being in southern super hot FL. Had car since new.