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Why do we change oil?

7K views 18 replies 11 participants last post by  Renfrick1 
#1 ·
This thread is not meant to cause controversy, but out of genuine curiosity.
What is your reason behind needing an oil change? Is it because of dirtied oil or because of some arbitrary number of miles a manufacturer or your mind has told you that the oil has surpassed its ideal lifespan?

I was planning on changing my full synthetic oil (I shall not name the brand in order to prevent a brand war, and because I’m I’m not being paid to sponsor) at 10,000 miles but it has been pushed back and now has hit 12,000 miles. I checked the dipstick, and that stuff is near golden... i see no reason to change it. Seems to be a waste of time, money, and honestly perfectly good oil. With a clean air filter keeping debris out of the engine, and high mileage oil filter and oil, I see no reason to change before starting to see signs of dirty oil. With modern day full synthetic’s, there is practically no break down of the oil in such low heat conditions. I have never broke 230 degrees oil temp even while towing decent weight in summer heat.
Vehicle in mention is a 300c with a 5.7 L engine. I plan on running for another 3,000 miles to reach 15k on the oil, and sending the oil in for analysis if all looks well.
 
#3 ·
Because people with more letters behind their names than I have IN my name have spent MILLIONS of dollars and years of time to research how long your oil should last before the lubricity/viscosity becomes hazardous to the lifespan of your engine. Hence the manufacturer recommendation.

I say go for it though. Why not stretch it out to 20, 30 or even 50k miles? While you're at it, don't bother changing the air filter, rotating or even replacing tires. Never change the trans fluid or rear diff fluid either. It's all sealed up and dirt free right?

Am I being obstinate? Yes. With ever fiber of my being and I won't apologize for it either.
 
#4 ·
Because people with more letters behind their names than I have IN my name have spent MILLIONS of dollars and years of time to research how long your oil should last before the lubricity/viscosity becomes hazardous to the lifespan of your engine. Hence the manufacturer recommendation.

I say go for it though. Why not stretch it out to 20, 30 or even 50k miles? While you're at it, don't bother changing the air filter, rotating or even replacing tires. Never change the trans fluid or rear diff fluid either. It's all sealed up and dirt free right?

Am I being obstinate? Yes. With ever fiber of my being and I won't apologize for it either.
You say that in jest, but there are a whole lot of folks out there that do just that.......and they usually either end up paying for it in the long run or dump the vehicle onto some unsuspecting victim. I have a niece that did that to her Suburban and ended up wasting the engine. Some folks have to live and learn the hard way. Personally, I use top quality synthetic oils/fluids in everything.....engine, transmission, differentials and on the 4WD the transfer case too. I also you a high quality oil filter in the engine. My engine oil is changed every 6000 mi. and everything else is changed at 30000 mile intervals. My philosophy......oil/fluids and filters are a whole lot cheaper than the components they're hopefully protecting.
 
#6 ·
I'm an old codger. My Dad changed the oil in his vehicles back in the 50's and 60's every 2,000 miles. Those old Chevy 6 bangers prior to 63 would be worn out and pumping oil by 60,000 miles anyway. I have been changing the oil in my vehicles every 5k miles because it's easy to keep up with. Do I need to change it that often? I don't know but I do it myself and it doesn't cost that much. I do believe that if you run it 10k miles or more the engine will sludge up quicker. And some of today's engines running at higher tempertures with cam phasers and other stuff working off oil pressure, it might be a good idea to keep the sludge out.
 
#9 ·
I'm an old codger. My Dad changed the oil in his vehicles back in the 50's and 60's every 2,000 miles. Those old Chevy 6 bangers prior to 63 would be worn out and pumping oil by 60,000 miles anyway. I have been changing the oil in my vehicles every 5k miles because it's easy to keep up with. Do I need to change it that often? I don't know but I do it myself and it doesn't cost that much. I do believe that if you run it 10k miles or more the engine will sludge up quicker. And some of today's engines running at higher tempertures with cam phasers and other stuff working off oil pressure, it might be a good idea to keep the sludge out.
I hear you on the "old codger"......me too. I remember to that when we took long trips, Dad would stop and get the oil changed, sometimes 2 or 3 times over 5000-6000 miles. I've had the heads off of all three of my Hemi's and, I can tell you that today's oils/fluids are really the "cat's meow". The engine innards look like brand new and I could still see the factory honing cross hatch marks on the cylinder walls....the 6.1 after 164K miles.....zero sludge anywhere.
 
#10 ·
Oil is cheaper than an engine would be my main reason. An ounce of prevention is worth a pound of cure, yeah? No matter how it looks, chemistry is happening inside the ol' internal combustion engine and that oil is not as it was out of the bottle - it's been contaminated in some way.

To know what's really going on why not have a used oil analysis (UOA) done? They're $20-40 through Blackstone, Polaris/Amsoil, Wix, CAT, et cetera. Send in an unused virgin sample and a current sample to compare them. There will be a difference.

The key value is Total Base Number (TBN) as it indicates the amount of additives left before diminishing to become acidic and letting sludge form. The site BobIsTheOilGuy has articles fully explaining how to interpret an analysis and then there's the associated forums if you really want to go down the rabbithole.

If you really want to see how far you can extend your oil change interval, supplement the standard full-flow 20-micron filter with a 2-micron bypass filter!
 
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#13 ·
I worked with a brilliant mechanical engineer in Wisconsin for a couple of years. His brother who has a degree in chemical engineering worked for Conoco in Texas. He said his brother saw the results of a test where they ran engines for 100,000 miles with synthetic oil and they held up fine so he never changes the oil in his vehicles, just changes the filter occasionally and adds oil as needed. I can't do that. I have a mental block.
 
#17 ·
Lifetime bumper to bumper warranty, i won't change my oil for another 5 years. Its been 11 years so far, i change engines more than oil.:stir:



:bahdumcha: LOL
 
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#18 ·
My BIL ran synthetic and changed the oil on his HEMI pickup every 15k, and bought a new engine this spring - sludged and seized some lifters I believe. I saw the pictures of when they took the valve covers off, no idea what the oil in the pan looked like. Dirt, soot, carbon show up in the oil, but I don't know that Nitrogen based contaminates the exacerbate sludging are visible. The oil change indicator is based on number of revolutions turned and oil temperature and is a good tracker of the oil life (very high and very low temps shorten oil life, friction additivies can only handle so many shear events), and it's capped to make sure you don't over do it for sludging too. Trust your local powertrain engineer.
 
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