How long between oil changes with full synthetic?
#1
Racer
Thread Starter
How long between oil changes with full synthetic?
With this semi-synthetic oil that's coming with the free oil changes at the dealer would only give me about 7k miles between oil changes. I'm at 18,500 miles so I only have one more free one. I plan to switch to full synthetic after that. Should that give me more miles between oil changes? The customer service guy at the dealership said the factory programmed the car to only get 7K miles between oil changes whether it's full or semi synthetic but a local mechanic said the car should monitor for carbon in the oil and adjust accordingly.
#2
Race Director
I go by the Oil Life Monitor primarily. As per the manual also, do not surpass 1-year. Beyond that, I tend to use 5,000 miles as a guide for my vehicles. Having your oil "too clean" just helps protect your large investment.
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10K miles or 1 year between changes is usually considered sufficient except if you are tracking the car in which case you need to be running 15W50 during track events and then putting 5W30 back in. Most Corvette owners are **** (like me) and tend to change their oil more often than is really necessary. In my case every 6 months or about 5K miles. Probably overkill but makes us feel better.
#6
Moderator
C7 Oil Life Monitor takes time since last change (monitor reset) into account. Even if you put zero miles on your car, the OLM will read zero at 1 year. Follow your OLM (unless tracking as rmorin1249 states).
OP, your dealer customer service guy is probably off base on his description of the OLM. It use a lot more than miles to calculate the oil life remaining.
Here is an interesting read on the OLM system that I posted a while back:
OP, your dealer customer service guy is probably off base on his description of the OLM. It use a lot more than miles to calculate the oil life remaining.
Here is an interesting read on the OLM system that I posted a while back:
The following interesting post about the GM Oil Life Monitoring System is posted on BobIsTheOilGuy:
The system on the C5 and C6 did not seem to factor in time since last oil change (monitor reset). The C7 definitely does factor in elapsed time and will register 0% at a year.
One thing I can touch on and clear up.....the GM oil life monitor operation and my statement that ZDP (or ZDDP as you tend to call it here...most of the API literature just sticks to ZDP so I tend to use that) depletion is the basis for oil deterioration.
My spelling is poor but ZDP stands for zinc dialkyldithiophosphate which , as it sounds, is an anti-wear compound comprised of zinc and phosphorus.
ZDP is dispersed in the oil so as to be at a potential wear site if a surface asperity happens to break thru the oil film thickness causing the dreaded metal-to-metal contact. A molecule of ZDP must be present at that moment to prevent microwelding at the contact site which will cause material transfer, scuffing, scoring, wear and catostrophic failure. The concentration of ZDP in the oil will determine if there is ZDP present to work it's magic. The greater the concentration...the more likely a molecule of ZDP will be there...and vice versa.
By nature, ZDP is sacrifical. As ZDP is "used up" at a wear site to prevent micorwelding the concentration of ZDP decreases.... So...if you measure the ZDP concentration in engine oil in a running engine it will decrease at linear rate based on engine revolutions. Any given engine has a certain number of high potential wear areas where metal-to-metal contact could occur due to reduced film thickness and/or surface asperities....areas such as rubbing element cam followers, distributor gears, rocker arm pivots, push rod tips, etc...... The more of these areas the more ZDP depletion. The more often these features come in contact the greater the ZDP depletion. That is why, generally speaking, ZDP concentration in the oil, for any given engine, will decrease at a fairly linear rate when plotted versus cummulative engine revolutions. The more times it turns the more contact the more chance for wear the greater the depletion. This is as much of a fact as I could quote ever and is really not speculation or anything. It is proven beyond a shadow of a doubt in many studies. That is why it is ONE of the basis for determining oil life remaining and why it is THE basic premis of the GM oil life algorithm. It is only ONE of the things that determines oil life...but it is the one thing that can be tied to engine operation in a linear fashion and estimated very accurately by accumulating engine revolutions via a counter.
The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.
You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.
The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.
The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.
The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.
One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application. NOt something that oil companies or Amsoil do. They generalize....the oil life monitor is very specific for that application.
Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.
There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.
Please...NOT ALL ENGINES ARE THE SAME. The example above is an excellent practical justification of why you would want to add EOS and change the 15W40 Delvac in the muscle car at 3000 miles max and yet can run the Northstar to 12500 easily on conventional oil. You must treat each engine and situation differently and what applies to one does not retroactively apply to others. This is where Amsoil falls short in my book by proposing long change intervals in most everything if you use their oil. It just doesn't work that way. You can run the Amsoil to 12500 with no concerns whatsoever in the late model Northstar because even the oil life monitor tells you that for conventional oil off the shelf. Would I do that to the 502 in my 66 Chevelle...NO WAY. Amsoil says I can though. Wrong.
There are entire SAE papers written on the GM oil life monitor and one could write a book on it so it is hard to touch on all aspects of it in a single post. Hopefully we hit the high spots. Realize that a GREAT deal of time, work and energy went into developing the oil life monitor and it has received acclaim from engineering organizations, petroleum organizations, environmental groups all across the board. It is not some widget invented in a week and tacked onto the car.
My spelling is poor but ZDP stands for zinc dialkyldithiophosphate which , as it sounds, is an anti-wear compound comprised of zinc and phosphorus.
ZDP is dispersed in the oil so as to be at a potential wear site if a surface asperity happens to break thru the oil film thickness causing the dreaded metal-to-metal contact. A molecule of ZDP must be present at that moment to prevent microwelding at the contact site which will cause material transfer, scuffing, scoring, wear and catostrophic failure. The concentration of ZDP in the oil will determine if there is ZDP present to work it's magic. The greater the concentration...the more likely a molecule of ZDP will be there...and vice versa.
By nature, ZDP is sacrifical. As ZDP is "used up" at a wear site to prevent micorwelding the concentration of ZDP decreases.... So...if you measure the ZDP concentration in engine oil in a running engine it will decrease at linear rate based on engine revolutions. Any given engine has a certain number of high potential wear areas where metal-to-metal contact could occur due to reduced film thickness and/or surface asperities....areas such as rubbing element cam followers, distributor gears, rocker arm pivots, push rod tips, etc...... The more of these areas the more ZDP depletion. The more often these features come in contact the greater the ZDP depletion. That is why, generally speaking, ZDP concentration in the oil, for any given engine, will decrease at a fairly linear rate when plotted versus cummulative engine revolutions. The more times it turns the more contact the more chance for wear the greater the depletion. This is as much of a fact as I could quote ever and is really not speculation or anything. It is proven beyond a shadow of a doubt in many studies. That is why it is ONE of the basis for determining oil life remaining and why it is THE basic premis of the GM oil life algorithm. It is only ONE of the things that determines oil life...but it is the one thing that can be tied to engine operation in a linear fashion and estimated very accurately by accumulating engine revolutions via a counter.
The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.
You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.
The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.
The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.
The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.
One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application. NOt something that oil companies or Amsoil do. They generalize....the oil life monitor is very specific for that application.
Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.
There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.
Please...NOT ALL ENGINES ARE THE SAME. The example above is an excellent practical justification of why you would want to add EOS and change the 15W40 Delvac in the muscle car at 3000 miles max and yet can run the Northstar to 12500 easily on conventional oil. You must treat each engine and situation differently and what applies to one does not retroactively apply to others. This is where Amsoil falls short in my book by proposing long change intervals in most everything if you use their oil. It just doesn't work that way. You can run the Amsoil to 12500 with no concerns whatsoever in the late model Northstar because even the oil life monitor tells you that for conventional oil off the shelf. Would I do that to the 502 in my 66 Chevelle...NO WAY. Amsoil says I can though. Wrong.
There are entire SAE papers written on the GM oil life monitor and one could write a book on it so it is hard to touch on all aspects of it in a single post. Hopefully we hit the high spots. Realize that a GREAT deal of time, work and energy went into developing the oil life monitor and it has received acclaim from engineering organizations, petroleum organizations, environmental groups all across the board. It is not some widget invented in a week and tacked onto the car.
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#8
Racer
Thread Starter
My C6 lasted about 16K miles between oil changes with full synthetic. That car made it to 274K miles (yes 2-7-4) before I sold it. I drive way too much to much to be getting it changed every 5K miles if not necessary. I've only had my C7 since 1/1/15 and it has 18,500 miles.
The mechanic I spoke to said if you go to full synthetic you can never go back to semi synthetic so I was hoping to know if I would get increased drive time between oil changes. What I gathered from that extensive post from another thread is it sounds like the car will get increased miles between oil changes with the full synthetic which is great news.
Thanks
#9
Safety Car
The mechanic I spoke to said if you go to full synthetic you can never go back to semi synthetic so I was hoping to know if I would get increased drive time between oil changes. What I gathered from that extensive post from another thread is it sounds like the car will get increased miles between oil changes with the full synthetic which is great news.
Thanks
Thanks
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
#10
Drifting
The mechanic you've been talking to is an idiot. Everything you've said he told you is incorrect. You can switch between synthetic, blend and full dino oil whenever you want. All modern oils that meet the Dexos spec are compatible. And whether you can go 7K miles on semi-synthetic, or more, or less, will depend on how you use the car.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
#12
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#13
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The mechanic you've been talking to is an idiot. Everything you've said he told yohhu is incorrect. You can switch between synthetic, blend and full dino oil whenever you want. All modern oils that meet the Dexos spec are compatible. And whether you can go 7K miles on semi-synthetic, or more, or less, will depend on how you use the car.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
Last edited by JerryU; 10-09-2015 at 07:18 PM.
#16
Drifting
The mechanic I spoke to said if you go to full synthetic you can never go back to semi synthetic so I was hoping to know if I would get increased drive time between oil changes. What I gathered from that extensive post from another thread is it sounds like the car will get increased miles between oil changes with the full synthetic which is great news.
Thanks[/QUOTE]
That "mechanic" may have also asked you if you wanted fries with that since it sounds like he just came from his last job that required him to ask all his customers that question.
Thanks[/QUOTE]
That "mechanic" may have also asked you if you wanted fries with that since it sounds like he just came from his last job that required him to ask all his customers that question.
#17
C7 Oil Life Monitor takes time since last change (monitor reset) into account. Even if you put zero miles on your car, the OLM will read zero at 1 year. Follow your OLM (unless tracking as rmorin1249 states).
OP, your dealer customer service guy is probably off base on his description of the OLM. It use a lot more than miles to calculate the oil life remaining.
Here is an interesting read on the OLM system that I posted a while back:
OP, your dealer customer service guy is probably off base on his description of the OLM. It use a lot more than miles to calculate the oil life remaining.
Here is an interesting read on the OLM system that I posted a while back:
#18
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The mechanic you've been talking to is an idiot. Everything you've said he told you is incorrect. You can switch between synthetic, blend and full dino oil whenever you want. All modern oils that meet the Dexos spec are compatible. And whether you can go 7K miles on semi-synthetic, or more, or less, will depend on how you use the car.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
He also shouldn't be putting semi-synthetic in your car. GM reimburses dealers for Mobil 1, so he's ripping you off. Time to find a new dealer.
Can you go further between changes on full synthetic? Maybe. A lot will depend on your driving style and the usage of the car. But unless you're going to do oil analyses periodically to check the condition of the oil you have no way to tell whether it's safe to go longer or not. You can't tell by looking at the oil, smelling the oil, putting drops on a paper towel, or by how many miles the car has been driven.
And going longer than the OLM tells you could give GM reason to void the warranty on your engine if anything goes wrong.
GM spent millions developing and testing the OLM system. They know more than your stupid mechanic. Change it when the DIC tells you to.
#19
Melting Slicks
#20
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