Mixing Oils?

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I was thinking about doing an oil change now. and just wanted some thoughts. would it be a good idea to mix convential oil with a synthetic to get the blend that I want or will it just degrade both oils that I mix? I am not sure you can even mix oils but just curious. Thank you
 
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Oils can be mixed, conventional and synthetic in any combination, that is they are miscible, but you'd have no idea if the new mixture would meet any specification listed on either bottle. Your new mixture would be the result of combining two unknown quantities of oil and to what purpose. People mix oils, sometimes in an effort not to waste oil left over from a previous oil change or oil from a bargain purchase and never have a problem. A simple solution would be to pick one or the other and be satisfied with a product designed to meed a given spec or list of spec's on the bottle once you've gradually used up your stash.
 
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Well yes, you can mix oils without problem, but general consensus here is that this practice is not beneficial and can cause different additives to interact in a way that is not best for the engine. I should also mention that there was some very good UOAs with various oil mix on this forum, so this is all pretty much hypothetical. Today you can buy variety of synthetic, blend or mineral oils for cheap so there's no point in mixing them especially on purpose. If you have some leftovers then use it by all means.
 
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Originally Posted By: tig1
M1 does not recommend mixing different oils. Here is there link. http://www.mobiloil.com/USA-English/Moto...tional_Oil.aspx
Really? So Caterham called their tech line inquiring about mixing oils and their tech said it was absolutely fine. So which is it. And redline not only says it's fine they even recommend it so a person can fine tune the viscometrics for a specific application. So I guess I should expect my clean engines to sludge up now,or suffer some form of lubrication failure. Tig I suggest taking that q&a from mobil with a grain of salt. They are of course trying to sell THEIR product and of course will discourage any thoughts of mixing their superior product with another brand. And you are aware that in order to carry an API starburst the lubricant must be miscible with other branded api starburst lubricants,aren't you? Tig why don't you dig up one of the many frankenbrew uoa posted in the forum and prove that mixing is bad. A uoa is proof positive that mixing is bad,right? I'll save you the trouble. Not a single uoa posted here of a frankenbrew showed any problems whatsoever. In fact in the many examples here of a frankenbrew wear metals tended to be lower than the universal averages(not that it in itself means much)and I've never seen a uoa that showed anything even close to abnormal. So since the api mandates that to carry their star an oil has to mix safely with other brands,and since I mix different brands at almost every oil change and my engines internals are spotless,and since every frankenbrew uoa posted in this fine forum says no problem I'm gonna call bovine carp here. I saw a quote yesterday from a mobil rep yesterday that states under no uncertain terms that the word synthetic as it applies to oil is a marketing term,so should we then conclude that mobil oils basestocks reflect that statement or......
 

OVERKILL

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Originally Posted By: Clevy
Originally Posted By: tig1
M1 does not recommend mixing different oils. Here is there link. http://www.mobiloil.com/USA-English/Moto...tional_Oil.aspx
Really? So Caterham called their tech line inquiring about mixing oils and their tech said it was absolutely fine. So which is it. And redline not only says it's fine they even recommend it so a person can fine tune the viscometrics for a specific application. So I guess I should expect my clean engines to sludge up now,or suffer some form of lubrication failure. Tig I suggest taking that q&a from mobil with a grain of salt. They are of course trying to sell THEIR product and of course will discourage any thoughts of mixing their superior product with another brand. And you are aware that in order to carry an API starburst the lubricant must be miscible with other branded api starburst lubricants,aren't you? Tig why don't you dig up one of the many frankenbrew uoa posted in the forum and prove that mixing is bad. A uoa is proof positive that mixing is bad,right? I'll save you the trouble. Not a single uoa posted here of a frankenbrew showed any problems whatsoever. In fact in the many examples here of a frankenbrew wear metals tended to be lower than the universal averages(not that it in itself means much)and I've never seen a uoa that showed anything even close to abnormal. So since the api mandates that to carry their star an oil has to mix safely with other brands,and since I mix different brands at almost every oil change and my engines internals are spotless,and since every frankenbrew uoa posted in this fine forum says no problem I'm gonna call bovine carp here. I saw a quote yesterday from a mobil rep yesterday that states under no uncertain terms that the word synthetic as it applies to oil is a marketing term,so should we then conclude that mobil oils basestocks reflect that statement or......
Clevy: In case you missed this: http://www.bobistheoilguy.com/forums/ubb...922#Post3503439 Gives a nice perspective on that miscible spec that you are quoting.
 
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Yes I mix, have mixed for 30 years...and I'm avoiding it into the future, from what I've learned the last few months. I was relying on the quoted ASTM standard, and how it's been represented in BITOG, but a simple search and read of the standard is that it's miscibility, the ability of an oil to be blended with 6 reference oils and not form chunks...not that they will be compatible with everything on every shelf...that's inferred, and the likelihood of immiscible oils is small. The miscibility standard does not imply, infer, or even guarantee that the end result meets any single one of the tests that each oil can do on it's own, wear protection, and importantly the cold cranking end of the spectrum, which is where the unfavourable parts seem to occur. e.g. discussion here (and yes, I took a 5W20/20W60 mix out of my mower if you read the next post). "normal" temperatures, you probably will never have anything that resembles an issue (the linked taxi issues appear to have caused problems and wear at "normal" temps, however). If you are relying on starting in extreme temps, stick to a brand if you can.
 

98xj4o

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I have a jeep amc 4.0 Motor with 141,000 on it I don't know what motor oil was used in the past and I was considering using a quart or two of mobile one or royal purple to receive the benefits of the synthetic oils with the rest being some sort of conventional oil with out opening up any seals or leaks. would be my goal. I am not sure if this seems like a good idea. but with Clevy mentioning about the frankenbrews it seems like a good idea to do this mixture?
 

Nick1994

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Originally Posted By: 98xj4o
I have a jeep amc 4.0 Motor with 141,000 on it I don't know what motor oil was used in the past and I was considering using a quart or two of mobile one or royal purple to receive the benefits of the synthetic oils with the rest being some sort of conventional oil with out opening up any seals or leaks. would be my goal. I am not sure if this seems like a good idea. but with Clevy mentioning about the frankenbrews it seems like a good idea to do this mixture?
The Jeep 4.0L will run on just about anything. I've heard they get noisy with Mobil 1 though. Last week I changed the oil on my grandpa's 96' Cherokee with the 4.0L to Pennzoil Platinum and a Fram Ultra filter. Runs great, no leaks although it has a new oil pan gasket and rear main seal
 

CT8

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passenger car motor oils can be mixed by design. You will fortify the weaker oils or dilute the stronger oils. There is not a whole lot of difference between them as far as mixing goes.
 
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Originally Posted By: CT8
passenger car motor oils can be mixed by design. You will fortify the weaker oils or dilute the stronger oils. There is not a whole lot of difference between them as far as mixing goes.
So we should ignore what a twelve year member who's an engineer posts and take your word for it? The real concern is what happens to the cold temperature performance with the blend. This may not be much of a concern in most of Cali, but it is for many of us.
 
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It is silly to say that passenger car motor oils can be mixed by design. Oils differ in what requirements they meet and their viscosity. I certainly would not want to mix 5W30 oil and 0w30 oil in a car that was designed to operate with 0W30 oil. And what about diesel engine oil compared to gasoline engine oil? The last time I checked GM was still recommending 5W30 oil in their cars. Ford recommends 5W20 the last time I checked. This is for gasoline engine cars. In any case, why mix differing motor oils? If you know the oil in a car engine is 5W20 Motorcraft oil, why not use 5W20 Motorcraft oil which is readily available? In an emergency you certainly could use a different brand. But it would probably be best to stick to the proper viscosity. There is probably no harm in mixing brands (of the same viscosity) but personally if I knew that the oil in an engine was 5W30 GM oil I think I would want to use that oil if I needed to add oil, if it was available. And there are even certain cars where synthetic motor oil is required. There have been cars that had 15W50 Mobil 1 in them when they came from the factory. In the very least a person wants to use motor oil of the correct viscosity and motor oil with the correct requirements (such as diesel vs gasoline and so forth). In an emergency some oil is better than no oil but if I was using Pennzoil 5W30 in a car engine and I needed to add some oil I would try to get some 5W30 Pennzoil oil.
 
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Originally Posted By: Clevy
Originally Posted By: tig1
M1 does not recommend mixing different oils. Here is there link. http://www.mobiloil.com/USA-English/Moto...tional_Oil.aspx
Really? So Caterham called their tech line inquiring about mixing oils and their tech said it was absolutely fine. So which is it. And redline not only says it's fine they even recommend it so a person can fine tune the viscometrics for a specific application. So I guess I should expect my clean engines to sludge up now,or suffer some form of lubrication failure. Tig I suggest taking that q&a from mobil with a grain of salt. They are of course trying to sell THEIR product and of course will discourage any thoughts of mixing their superior product with another brand. And you are aware that in order to carry an API starburst the lubricant must be miscible with other branded api starburst lubricants,aren't you? Tig why don't you dig up one of the many frankenbrew uoa posted in the forum and prove that mixing is bad. A uoa is proof positive that mixing is bad,right? I'll save you the trouble. Not a single uoa posted here of a frankenbrew showed any problems whatsoever. In fact in the many examples here of a frankenbrew wear metals tended to be lower than the universal averages(not that it in itself means much)and I've never seen a uoa that showed anything even close to abnormal. So since the api mandates that to carry their star an oil has to mix safely with other brands,and since I mix different brands at almost every oil change and my engines internals are spotless,and since every frankenbrew uoa posted in this fine forum says no problem I'm gonna call bovine carp here. I saw a quote yesterday from a mobil rep yesterday that states under no uncertain terms that the word synthetic as it applies to oil is a marketing term,so should we then conclude that mobil oils basestocks reflect that statement or......
Back off big guy, you're on a rant again. WWF
 
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New oil inevitably mixes with some old lubricant and its spent additives during each OC in all of my machinery. None of them have yet been reduced to a soldering heap.
 
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if you could not mix oils there would be lots of dead cars and trucks on the road because the average person looks for the cheapest oil change place and gets their oil changed there and next time whoever does it the cheapest is the one they use most just think oil is oil and for the most part that is correct
 
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I think that you mean "smoldering", and knocking down your own strawman doesn't make an argument. http://papers.sae.org/2000-01-2942/
Quote:
A significant deterioration in low temperature pumpability properties (as measured by the mini-rotary viscometer; MRV) was observed in certain commercial-quality engine oils in a taxi field test program. A detailed investigation demonstrated that contamination by carry-over of the factory fill oil in combination with oil aging was the cause of the marked deterioration in low-temperature pumpability properties; no evidence of new oil incompatibility was observed using industry-standard test procedures. A subsequent investigation identified a number of commercial ILSAC GF-2 quality engine oils which also caused large MRV viscosity increases when added in concentrations as low as 1 wt% to used engine oils. A root-cause evaluation established that low concentrations of certain viscosity index improvers caused large MRV viscosity increases when added to used oils. Results from this investigation suggest that a new industry standard may be required to ensure used oil compatibility over a lubricant's normal drain interval.
Not very often, but sometimes bad stuff happens when you mix...and the compatibility tests aren't geared for that "not very often" to "quite rare" moment.
Originally Posted By: Miyagi
The Best Defense Is No Be There.
 
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I've maintained three different engines all averaging 250K before departing and I mixed oils at almost every OCI of their lifetimes. I buy all my vehicles new and usually am first & last owner. You can mix Mobil with Valvoline or Pennzoil with Castrol and it won't hurt a thing, provided you change your oil regularly. I work on a rule that when checking my oil once a week, if it's black by 1.5K of the OCI, I am not changing my oil enough. I like my oil dipstick to be 'at least" semi-clear at 1.5K. If it's shows black at 2K, I'm OK with it. My synthetic drains are usually 7.5K. My 50-50 semi-synthetic drains are at 6K. My dino drains are at 4k.
 
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