According to GM engine design they are definitely related! The 4.6 Northstar is a shining(?) example. Designed for 300,000 miles but 1 qt./ 1000 is considered normal usage! Not unusual to open an engine with 100,000 miles+ on it and still be able to see the original hone pattern on the cylinder walls! The real problem is the wide viscosity rated oils rely on VI improvers that lock up the rings in short order if driven gently...increasing oil consumption. Hence the STRICT 10W-30 vis. recommendation from GM (up to 1999 m/y at least). Use of synthetic oil is discouraged probably due to the resulting high cost/mile.
Once again, highly discouraged by Cadillac engine designers. You may be correct Dr. T, but I need more facts before doing that expieriment. What do you suppose would be the long term effects of a "heavy" synthetic on a Northstar with stuck rings/excessive oil consumption? Probably just a lighter wallet. What about 0W-30, purported to be "thicker" than 10W-30 M1? What if the owners manual were completely ignored right from the start and 0W-50 put in at 2000 miles? Regardless, the question was if oil usage and wear had any correlation. The answer is still yes according to GM. They may have applied this theory or design concept to the Saturn engine as well.
M1 0w30 may be "thicker" as in it flows slower at 100C. (only slight anyway) But its film thickness especially at the RINGS, cam and bearings is thinner.
I am refering to HTHS, a much better measurement to go by IMO.
[ February 26, 2003, 10:29 AM: Message edited by: Jason Troxell ]
I think if you have oil consumption then you have blow-by which is contaminating the oil. The fuel is thinning it, lowering the oils viscosity and the vicious cycle keeps getting worse. Then you dump the oil and start the degradating circle all over again. So yes I believe the two are related.
Chris, That depends on what your definition of "is" is. It just sounded familiar, sorry. No, really, blowby may actually be designed in to these engines! The only difference is that gasoline is not going into the oil, but oil going into the combustion chamber. Hence the new SL oils, which are easier on Catalytic converters. Starting to get the picture? The hone pattern on new GM Northstar engines is VERY aggressive. This is done to keep the rings VERY well lubricated promoting a very long engine life. Unfortunately, it manifests itself to the consumer as excessive oil consumption. Now couple that to the fact that most of us keep our engines OVERFULL on oil, resulting in some being scavenged off by the PCV valve, and you have real oilburner...right from the factory! How many of us check our engine oil with it HOT? That's what the manual tells us to do. Now thermal expansion on 7.5 quarts of oil(the capacity of a Northstar) can make a significant difference. I now keep mine on the "ADD" mark...giving me 7 quarts in the pan(cold). The engine is designed to run, full tilt, on 5 without doing harm.
It's all nonsense. You will NOT be experimenting. If it's not below -20 F in your area you can easily begin to use a 5-40 eg. Havoline Synth. and watch the consumption decrease from the water thin M-1 5-30's...then try going thicker. There CANNOT be any damage as long as the lubricant reaches all areas eg. it's not below the lubricant's pumpability limit...and screw GM and their water-for-oil recommendations. If anything...you will notice a smoother running engine and smoother power delivery. HT/HS is good so that one can rule out wear, but a thin oil will end up out the exhaust...even on new(er) engines...it's just up to the task...
Don't most all engines have compression rings to keep most of the combustion gases in the combustion chamber and oil control rings to keep most of the oil in the crankcase?
A very likely cause of oil consumption these days in cars that don't have really high mileage is the oil rings stuck in the ring groove from baked on carbon. Engine makers have been designing engines with shorter piston skirts for several reasons, and one result is that the oil rings are closer to the hot piston crown. The oil gets cooked in the ring groove oil drain holes and ring grooves, the oil rings can't do their job, and the engine burns oil. Here's one example...look at the photo of one of GM's not-so-better pistons: http://members.tripod.com/gmpistonslap/photos.htm
Actually the original post was not Northstar specific, just my answers. Reason for that is simply that I have a Northstar with the dreaded excessive oil consumption problem. Also, have been in constant contact with a GM Northstar engine designer for the last several months and these were the explanations/recommendations that came directly from him. To be fair, I alluded to the Saturn engine as another possible example of similar engineering and design.
From the included link, I must assume this could be part of the HUGE GM PISTON SLAP COVERUP!
Dr. T, I am not currently using M1 10-30, but when I did try it, oil consumption increased, so you may be right about the heavy oil. Problem is, I switched to conventional Mobil Drive Clean in the 10W-30 grade and consumption dropped significantly, as well as my oil cost/mile. The only other adjustment that I made was lowering my oil level when cold from the "FULL" mark to the "ADD" mark. The other problem is that GM does not recommend it and quotes possible engine damage as a result.
Keep in mind, I don't have a dog in this hunt! I'm only trying to learn from all of you experts, and adding the facts as they have been given to me. Do any of you think we can resolve the great motor oil mystery anytime soon? Probably no more than we'll see peace in the Middle East in our lifetimes!