OK to put synthetic oil in high mileage car?
Registered User
Joined: Dec 2004
Posts: 45
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From: SF Bay Area, CA
What I meant was for him to go from dino to synthetic blend as a way of trying it out. Besides, synthetics are completely compatible with non-synthetics, so I don't see why not.
This whole synthetic in a high mileage vehicle revolves around the detergents that synthetic oils have. If there is a lot of grit & sludge, synthetic will clean it out and expose leaks that might have been "covered up." However, synthetics can also condition the rubber seals...there was an article on this.
All speculation aside, why not try it out for yourself? I switched to synthetic at 190K miles and have not had a problem. My buddy also switched at 140K miles and no problems either. The bottom line is that if your car has been abused (infrequent/long OCI's), you will see increased leaking. Just weigh the pros and cons and make an informed decision!
This whole synthetic in a high mileage vehicle revolves around the detergents that synthetic oils have. If there is a lot of grit & sludge, synthetic will clean it out and expose leaks that might have been "covered up." However, synthetics can also condition the rubber seals...there was an article on this.
All speculation aside, why not try it out for yourself? I switched to synthetic at 190K miles and have not had a problem. My buddy also switched at 140K miles and no problems either. The bottom line is that if your car has been abused (infrequent/long OCI's), you will see increased leaking. Just weigh the pros and cons and make an informed decision!
Registered User
Joined: Dec 2004
Posts: 45
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From: SF Bay Area, CA
Originally Posted by StreetRacingCRX
You cannot mix conventional motor oil with sythentic, ask any mechanic. I have 60k miles and I use Mobil 1 and never had any problems
"Can different synthetic motor oils be mixed together?
Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way. "
A quote from a Subaru enthusiast:
"At one time you could buy detergent free oil and detergent oil (as is the norm today), and additive packages that were "ashless" and some that were not. The ashless oils left less deposits in engines that typically burned several times the oil a modern engine will burn. Many years ago the additive packages did not play well with others and some of those oils would cause problems if mixed. Since auto manufactures have moved to standardized oil performance standards that is no longer a problem. Any oil that meets your manufactures basic service requirements can be mixed without harming the engine. You may see slight changes in extreme condition performance but nothing to worry about.
The oil suppliers and service stations fed this belief as a way to ensure customers kept coming back for service instead of buying oil where ever they found it at the best price. By and large all those issues disappeared in the late 1960's and early 1970's during the oil embargo when folks out of need bought what ever they could find, and discovered nothing bad happened."
Other oil manufacturer websites will tell you teh same thing; I've checked Amsoil, Shell, and Castrol to name a few. Here's a link for reference:
http://www.shell.ca/code/motoring/en...etic_oils.html
From that article:
"All grades of Shell oils, synthetic and conventional, can be mixed with no compatibility issues....Incompatibility of engine oils refers to observations such as additive dropout, or changes in fundamental oil performance that's not what one might expect from mixing two different oils together," Miller says. "But naturally, if you mix oils with different characteristics, you're actually blending those characteristics - you've changed some of the features of the oil."
Do your own research and make an informed decision (as well as claims).
Thread Starter
Junior Member
Joined: Aug 2002
Posts: 25
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From: Ottawa, Canada
I've been very dilligent in changing my oil every 5K km, so I'm assuming my engine should be pretty clean inside and relatively sludge free. Every time I change the oil, I don't see any goop or sludge coming out. I might give it a try...it's just that it would be a shame if it started leaking or burning oil or something like that, when it's not doing it now.
Your Powder Coater
Joined: Mar 2004
Posts: 4,463
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From: Girard, Ohio
Originally Posted by doughboy_88
...from Mobil1's FAQ on their website:
"Can different synthetic motor oils be mixed together?
Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way. "
A quote from a Subaru enthusiast:
"At one time you could buy detergent free oil and detergent oil (as is the norm today), and additive packages that were "ashless" and some that were not. The ashless oils left less deposits in engines that typically burned several times the oil a modern engine will burn. Many years ago the additive packages did not play well with others and some of those oils would cause problems if mixed. Since auto manufactures have moved to standardized oil performance standards that is no longer a problem. Any oil that meets your manufactures basic service requirements can be mixed without harming the engine. You may see slight changes in extreme condition performance but nothing to worry about.
The oil suppliers and service stations fed this belief as a way to ensure customers kept coming back for service instead of buying oil where ever they found it at the best price. By and large all those issues disappeared in the late 1960's and early 1970's during the oil embargo when folks out of need bought what ever they could find, and discovered nothing bad happened."
Other oil manufacturer websites will tell you teh same thing; I've checked Amsoil, Shell, and Castrol to name a few. Here's a link for reference:
http://www.shell.ca/code/motoring/en...etic_oils.html
From that article:
"All grades of Shell oils, synthetic and conventional, can be mixed with no compatibility issues....Incompatibility of engine oils refers to observations such as additive dropout, or changes in fundamental oil performance that's not what one might expect from mixing two different oils together," Miller says. "But naturally, if you mix oils with different characteristics, you're actually blending those characteristics - you've changed some of the features of the oil."
Do your own research and make an informed decision (as well as claims).
"Can different synthetic motor oils be mixed together?
Mobil 1 is fully compatible with conventional motor oils, semi-synthetic motor oils and other synthetic motor oils, should it be necessary to mix them. However, it is important to note that the superior performance of Mobil 1 will be reduced by diluting it in any way. "
A quote from a Subaru enthusiast:
"At one time you could buy detergent free oil and detergent oil (as is the norm today), and additive packages that were "ashless" and some that were not. The ashless oils left less deposits in engines that typically burned several times the oil a modern engine will burn. Many years ago the additive packages did not play well with others and some of those oils would cause problems if mixed. Since auto manufactures have moved to standardized oil performance standards that is no longer a problem. Any oil that meets your manufactures basic service requirements can be mixed without harming the engine. You may see slight changes in extreme condition performance but nothing to worry about.
The oil suppliers and service stations fed this belief as a way to ensure customers kept coming back for service instead of buying oil where ever they found it at the best price. By and large all those issues disappeared in the late 1960's and early 1970's during the oil embargo when folks out of need bought what ever they could find, and discovered nothing bad happened."
Other oil manufacturer websites will tell you teh same thing; I've checked Amsoil, Shell, and Castrol to name a few. Here's a link for reference:
http://www.shell.ca/code/motoring/en...etic_oils.html
From that article:
"All grades of Shell oils, synthetic and conventional, can be mixed with no compatibility issues....Incompatibility of engine oils refers to observations such as additive dropout, or changes in fundamental oil performance that's not what one might expect from mixing two different oils together," Miller says. "But naturally, if you mix oils with different characteristics, you're actually blending those characteristics - you've changed some of the features of the oil."
Do your own research and make an informed decision (as well as claims).
This is great information & very informative.
Thanks for making such a great post!
Senior Member
Joined: Jun 2002
Posts: 2,033
Likes: 1
From: GA
Let me highjack this thread and dispose of another myth about OCI's
It's sad, but true. Oil companies and many quick lube operations know that synthetic oils are capable of extended drain intervals but are too afraid of lost revenue to admit it. In fact, here are a few quotes from different people in the automotive and lubrication industries which should illustrate what I mean:
According to GM's Mike McMillan, "Certainly there is technology available to raise the standard and extend the drain interval without compromising engine durability or removing the performance cushion ... Europe is already at a 9,000 mile drain interval and is seriously considering twice that".
Most other auto manufacturers agree. In the May 1996 issue of Lubes 'n' Greases representatives from the three major US auto makers detailed how lack of knowledge about available lubricant technology led to an unsatisfactory PCMO (Passenger Car Motor Oil) upgrade.
In response to this issue, GM has even come out with an oil life monitoring system for many of it's vehicles. Although it does not actually test the oil to determine its viability, it does monitor important system information to establish whether the oil is being exposed to conditions that would require a more frequent or less frequent change interval. The system isn't perfect, and it doesn't account for the long drain capability of synthetic oils, but it's at least a step in the right direction.
Even quick lube operations know that the technology exists to extend oil drains well beyond the 3,000 mile mark. Some are embracing extended drain technology as a way to increase customer satisfaction as well as company profits by working WITH the improvements in lubrication technology, instead of against them.
According to GM's Mike McMillan, "Certainly there is technology available to raise the standard and extend the drain interval without compromising engine durability or removing the performance cushion ... Europe is already at a 9,000 mile drain interval and is seriously considering twice that".
Most other auto manufacturers agree. In the May 1996 issue of Lubes 'n' Greases representatives from the three major US auto makers detailed how lack of knowledge about available lubricant technology led to an unsatisfactory PCMO (Passenger Car Motor Oil) upgrade.
In response to this issue, GM has even come out with an oil life monitoring system for many of it's vehicles. Although it does not actually test the oil to determine its viability, it does monitor important system information to establish whether the oil is being exposed to conditions that would require a more frequent or less frequent change interval. The system isn't perfect, and it doesn't account for the long drain capability of synthetic oils, but it's at least a step in the right direction.
Even quick lube operations know that the technology exists to extend oil drains well beyond the 3,000 mile mark. Some are embracing extended drain technology as a way to increase customer satisfaction as well as company profits by working WITH the improvements in lubrication technology, instead of against them.