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is it bad to mix different brands of motor oil?

Its the same weight.but diff brand..??

11 Answers

  • 1 decade ago
    Favorite Answer

    Brand doesn't matter as long they are the same Weight and Viscosity.

    i.e Mixing 10W-40W Semi Synthetic Oil with a 15W-50W Fully Synthetic Oil is not a good idea even if they are the same brand. However, you can mix a Mobil 10W-40W fully synthetic with a Castrol 10W-40W fully synthetic oil.

    Source(s): DIYer
  • 6 years ago

    lol. Seriously? Not one real life answer. I know this is an old question but someone might find it and believe any of the answers above. It doesn't matter if you mix the oils. Any oil you buy is going to be OK for your car(aside from cars that require synthetic specifically) because there are minimum standards for the companies that make oil. You can't buy a car oil that won't work. There are crappy and great oils but none of them are so bad your car won't work on them.

    If your car takes 10w30 and 5w20 and you put 3 quarts in and it doesn't mix - who cares? Your car will have 10w30 and 5w20 in the oil pan, both of which work just fine for your car. I assume the 10w30 is heavier and would get sucked up first. Within a few seconds the other oil will come through and it will all be mixed together. It might not completely mix but that doesn't change what the oil is doing in your engine. You still have oil that is rated for your car on the parts of your car. It doesn't matter which weight or if it is a blend of weights.

    The brand does not matter. Some oil might be better but has anyone even heard of anyone having an engine problem with mixing oils? It isn't like antifreeze where they expect you would use the same one permanently (ain't nobody changing that unless the engine is getting worked on 99% of the time and only topping off with water.) Manufacturers all expect that you will change your oil every 3-7500 miles and use a different oil many times. If 2 quarts in a 5 quart capacity engine caused your oil to turn to jello and destroy your engine then there would be no cars that leaked oil left on the road. People fill their car up constantly with whatever oil is at hand. Anyone who had a junk car that they had to put a quart a week in will tell you that they had 4-5 different oils and weights at any given time. The additives just don't do what people seem to be suggesting they do.

    Your car will not sound different. The oils will mix just fine under use and if they separate in the oil pan - who cares. 100 years of using random oils in cars proves that it doesn't hurt anything. If all of the oils you use were safe to begin with then the mixture of them will be fine.

    Finally, synthetic and regular oil can be mixed for all the aforementioned reasons. To top that off - Most synthetic oil is often the same oil as regular oil that has been refined further . Mobil 1 is one of the best "synthetic" oils you can buy and I believe the best selling. It isn't "synthetic" though. It is mineral oil with other things added. Thus making this a moot point unless you have special oil like german 0w30, redline, amsoil, or something that. If you had the money to have those oils then you wouldn't be asking this question to begin with and it wouldn't change the answer anyway.

    If I had 6 quarts of leftover oil for my truck from oil changes - I'd certainly use them and be confident knowing that everything was fine.

  • blea
    Lv 4
    4 years ago

    Brands Of Car Oil

  • 1 decade ago


    If you just need a quart to top off then it is ok but do not have a full oil change with 2 quarts of one and 3 quarts of another.

    Sometimes the brands have slightly different chemical properties that makes them not mix as well. A relative had a truck that he put a 2quart/3 quart brand mix into and one brand would always stay on the bottom of the oil pan on winter mornings and make the oil light go on until the truck fully warmed up. Once he changed the oil for 5 quarts of a completely same brand this didn't happen again even when the truck was still cold.

    Viscosity is the weight. You can mix viscosities as long as you use same brand oils and have a reason for doing this. I mixed up a slightly heavier weight oil than stock when I was using my car in the very hot desert highways. I went from a 10w/30 to roughly a 15w/45 by mixing 10w/30 with 20w/50 viscosity but same brand oil.

    You should most likely stay with the viscosity/weight oil that your car manual, mechanic, or dealership recommends.

    DO NOT MIX regular oil with semi- synthetic or full synthetic types though.


  • Anonymous
    5 years ago

    I even have been a mechanic for some years. this question has got here up extra cases than the different question. here is the technical answer to it. at the start each and every motor oil offered in the USA has to fulfill API/SM standards. If the oil you purchase does no longer have this pointed out image saying it meets API/SM customary, Then do no longer use it. If the logo is there and that they are the two the comparable weight, and comparable style of oil. (usual or guy made) Then any and motor vehicle manufactures ought to permit the oil for use in there automobiles. With that being reported, be chuffed to blend distinctive manufacturers of oil. I promise you that it will no longer injury your motor vehicle. API/SM is the common that each and every physique oil and motor vehicle agencies use as a instruction manual for applicable viscosity as properly simply by fact the degree of top quality used in production. If absolutely everyone tells you distinctive then i might have you ever seem it up with the dep. of weights and degree. as properly simply by fact the nationwide lubrication beginning place. I even have accomplished extensive learn. i wish this has helped you, and robust success.

  • 1 decade ago

    No not really, but I would stick to same quality brands, such as don't mix an off brand low quality oil with valvoline or something just because they might skimp on something in the cheaper oil. Mix two brands you trust/like that are the same "weight' and it will be fine. You won't hear any difference or anything.

    Source(s): Have done this many times as I buy oil that is on sale LOL
  • 4 years ago


    Source(s): Invest in Forex Tips
  • 7 years ago

    The W does not stand for 'weight'. It stands for 'winter'.

  • 1 decade ago

    Not really but I would not do that Cause different oil do different things that why there are so many different oils out there.

  • 1 decade ago

    No. It's the viscosity that you shouldn't mix. So using the same weight but say, Valvoline and Havoline will not be a problem. Just don't mix synthetic and regular oil.

    Source(s): Retired Mechanic
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