mixing of oils
mixing of oils
HellO! i have a ka24de and i drive normally septwhen i go on mountain passess about 1 - 3 times a week. i just recently got some mobil 1 synthetic 5w-30 and 15w-50 one says for gasoline engines the other says race proven and they have different SAE ratings, should i just ditch the 15w-50? could i mix 2 bottles of each? i got about 95k miles. thanks!!
If the SAE rating are differetn say SJ vs SL I wouldnt worry about too much, they are pretty similiar and many poils are still ebing sold as SJ but really meet SL.
Its generally ok to Mix if both are the same brand/ same kind oil just teh visocsities differnt.
It is difficult to predict how much teh viscvosity will change in the age of VII's and how stable the resulting weight is.
Still no major problems predicted.
Fred..
Its generally ok to Mix if both are the same brand/ same kind oil just teh visocsities differnt.
It is difficult to predict how much teh viscvosity will change in the age of VII's and how stable the resulting weight is.
Still no major problems predicted.
Fred..
this is a bit less of an issue with a full synthetic like MOBIL1 but here goes some oil formulation background ( much simplified):
lets say back in the day, up to about about 50 years ago, before the advent of multiviscosity oils, you had straight weights.
A 20 weight oil for winter which was generally not recommended for long hiway driving, a 30 weight oil for mild climates, a 40 weight oil for summers and 50 and 60 weight oils for hot summers and/or performance applications,. In the 50's and 60's multiviscosity oils were introduced, the first and most common grade was a 10w-30.
This means that in winter at 32 F, the oil poured like a 10 weight oil.But when heated up to 212F thinned out ONLY AS MUCH as a 30 weight WOULD!Clearly an incredible adavnce as you could now have an oil that can work well in winter and still work well on the hiway.
Other popular formulations were 10w-40's.
The way this was accomplished you took a 10 weight oil and added so called "viscosity index improvers" to it molecules that would bind to others tieing them together, as it got hotter and so preventing the oil from thinning out too much. Or if adding more VII's to the 10w base oil, a 10w40 was accomplished, of course there were limits to what you could do and to get to a 50 weight ( the standard summer grade then) you needed to start with a 20 weight base oil and then add VII's.hence the traditonal 20w-50 as a performance grade of today.
As these oils became popular, 2 limitations were discovered.
people were used to mixing a striaght 30 with a 50 weight and getting a 40 weight. now they found this was no longer true, the VII"s often acting unpredicably and mixing a quart of 10w-30 and 20w-50 was not neccesssarily making a 15w-40 ( sometimes it did and some times weird weights would occur ( 20w-30).
So mixing oils was harder now and best limited to grades that were close.
Also historically the main problem in keeping engines clean was sludge, which is the result of decomposing base oil under heat.But suddenly we were finding varnishes on our engine interiors.
Turns out VII's themselves can decompose and will deposit as varnish.
the greater the spread in an oil the more a varnish load it would put on the engine.
Today we have more stable VII's , but even so the majority of varnish in your engine comes from them.
despite these drawbacks the advantages of multiviscosity oils were too great and they have been with us ever since.
Synthetic oils need much less VII's, since their syn base stocks have a high built -in viscosity index anyway and the problem of varnish is much less with synthetics.
Also the dangers of unpredictable viscosities is much smaller when mixing synthetic oils.
Due to the innate VI of syn oils you can have a 0w-40 oil without excessive VII's.
Since less VII's used in syns like MOBIL1 we can use more of other additives like anti-wear anti rust, anti foam etc etc.Also we need less detergents in syn oils cuz they are less prone to varnish ( cuz less VII"s) and less prone to sludge ( better base oils) so we have alot more room for otehr additves like anti wear anti foam anti rust etc etc.
I hope this will give you enough background to understand my answer above.
Fred..
lets say back in the day, up to about about 50 years ago, before the advent of multiviscosity oils, you had straight weights.
A 20 weight oil for winter which was generally not recommended for long hiway driving, a 30 weight oil for mild climates, a 40 weight oil for summers and 50 and 60 weight oils for hot summers and/or performance applications,. In the 50's and 60's multiviscosity oils were introduced, the first and most common grade was a 10w-30.
This means that in winter at 32 F, the oil poured like a 10 weight oil.But when heated up to 212F thinned out ONLY AS MUCH as a 30 weight WOULD!Clearly an incredible adavnce as you could now have an oil that can work well in winter and still work well on the hiway.
Other popular formulations were 10w-40's.
The way this was accomplished you took a 10 weight oil and added so called "viscosity index improvers" to it molecules that would bind to others tieing them together, as it got hotter and so preventing the oil from thinning out too much. Or if adding more VII's to the 10w base oil, a 10w40 was accomplished, of course there were limits to what you could do and to get to a 50 weight ( the standard summer grade then) you needed to start with a 20 weight base oil and then add VII's.hence the traditonal 20w-50 as a performance grade of today.
As these oils became popular, 2 limitations were discovered.
people were used to mixing a striaght 30 with a 50 weight and getting a 40 weight. now they found this was no longer true, the VII"s often acting unpredicably and mixing a quart of 10w-30 and 20w-50 was not neccesssarily making a 15w-40 ( sometimes it did and some times weird weights would occur ( 20w-30).
So mixing oils was harder now and best limited to grades that were close.
Also historically the main problem in keeping engines clean was sludge, which is the result of decomposing base oil under heat.But suddenly we were finding varnishes on our engine interiors.
Turns out VII's themselves can decompose and will deposit as varnish.
the greater the spread in an oil the more a varnish load it would put on the engine.
Today we have more stable VII's , but even so the majority of varnish in your engine comes from them.
despite these drawbacks the advantages of multiviscosity oils were too great and they have been with us ever since.
Synthetic oils need much less VII's, since their syn base stocks have a high built -in viscosity index anyway and the problem of varnish is much less with synthetics.
Also the dangers of unpredictable viscosities is much smaller when mixing synthetic oils.
Due to the innate VI of syn oils you can have a 0w-40 oil without excessive VII's.
Since less VII's used in syns like MOBIL1 we can use more of other additives like anti-wear anti rust, anti foam etc etc.Also we need less detergents in syn oils cuz they are less prone to varnish ( cuz less VII"s) and less prone to sludge ( better base oils) so we have alot more room for otehr additves like anti wear anti foam anti rust etc etc.
I hope this will give you enough background to understand my answer above.
Fred..
WOW!! talk about droppin knowledge brotha! thanks a lot! this is very helpful and appreciative!! i am glad i can better understand oils now!! so basically whats going to happen when i mix my oils is that the rating will be somewhat unpredictable. so i am just going to use them independantly, !! one last question though, the race proven 15-50 is okay for my normal engine?? ownder's manual only says to use "labeled for gasoline engines" wheras the mobil 1 says "race proven"thanks again!!
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lessthanjakejohn
- Posts: 4105
- Joined: Fri Oct 25, 2002 6:39 am
Sorry to revive an old thread but, im looking to use mobil1 synthetic in my RB... but the RB's work really well with 10w40 which is not offered in the U.S. So could I just mix up some 10w30 m1synthetic and some 15w50m1synthetic and get something close to 10w40? Or will this create some weird unknown viscosity?
-Bluefire
-Bluefire