can conventional oil "top off" synthetic oil?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by cnschult, Apr 9, 2012.

  1. cnschult

    cnschult Active Member

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    I've found similar threads while searching but nothing that answers my question:
    You know the situation, you bought nice synthetic oil, a nice filter, took your time and did the job right, you figure it'll last 13,000 miles or so and after 8 or 9 thousand its time to top it off.

    My question is simple and you've probably already guessed it by now, why top off with expensive synthetic when its going to be drained out in a few thousand miles, why not just put in a few ounces of conventional?

    smart? stupid? pros/cons?

    I know most of you use Mobil 1, but I really love Pennzoil Platinum despite how crappy their conventional oil is, the conventional oil I have lying around is Mobil clean 5000 and I'd really love to get rid of it by topping off my corolla and both my prius but need the go-ahead by some engine experts here on priuschat, thanks.
     
    #1 cnschult, Apr 9, 2012
  2. Mike500

    Mike500 Senior Member

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    It would be perfectly fine, as long as it is the same viscosity.

    They make "blends" of synthetic and conventional oils, too.
     
    #2 Mike500, Apr 9, 2012
  3. cnschult

    cnschult Active Member

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    thanks Mike its funny you mention viscosity as my search on this issue mostly brought up people trying to mix viscosities, I do have a full jug of Ford Motorcraft 5w20 premium synthetic that I got years ago and sold the car it was for, I've never had the guts to use it in any of my two prius gen II's or corolla, not even my gen III Prius for the short time I owned it as it required 0w20. So since I never put oil in that is not specified on the oil cap I'll probably just sell it on craigslist, lots of Ford enthusiasts here in Michigan.

    I don't really see the point of synthetic blend and high mileage oil, we drive around 13,000 miles so an synthetic oil change every late October makes winter starts nice and easy. If I drove say 18,000 miles I would do a synthetic oil change in october followed by a conventional oil change in the summer. Even if I lived down south where cold winter starting wasn't an issue I would still use synthetic oil given the increased FE and similar cost/mile of full synthetic, not to mention it lasts over twice as long so less time under the car and less mess to clean up.

    so topping off my synthetic oil with conventional oil is okay because they sell synthetic blends, if that's your logic it makes sense to me as well, thanks.
     
    #3 cnschult, Apr 9, 2012
  4. The Electric Me

    The Electric Me Go Speed Go!

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    I think you guys right.

    You can probably top off with any oil, if you wish.

    But on the other hand?

    If we are just talking about adding a quart or less? Or as you suggest a few ounces? Why not just be consistent?

    Even the most expensive full synthetic is going to be less than $10.00 bucks a quart...

    If you are always doing your own oil changes, just buy in bulk and keep enough to account for the eventual top off.

    I guess my philosophy is there are so many things we are FORCED to spend a lot of money on, in the upkeep and maintenance of a vehicle, a marginal amount of savings vs. Topping off with "regular" or staying with synthetic just doesn't seem like an area I feel I need to pursue the marginal savings.
     
    #4 The Electric Me, Apr 9, 2012
  5. jdcollins5

    jdcollins5 Senior Member

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    I did not think you ever wanted to mix different motor oils, especially conventional and synthetic.
     
    #5 jdcollins5, Apr 9, 2012
  6. dogfriend

    dogfriend Human - Animal Hybrid

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    Most synthetic oils will state on the container that they are 100% compatible with conventional oil.
     
    #6 dogfriend, Apr 9, 2012
  7. jdcollins5

    jdcollins5 Senior Member

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    OK - but I think I will stick to my "old-fashioned" ways and let someone else try this :)
     
    #7 jdcollins5, Apr 9, 2012
  8. uart

    uart Senior Member

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    I normally prefer not to mix oils for an actual oil change (though I am sometimes tempted when I've got a few liters left over in various different bottles). For topping off however I don't really care too much about mixing them.

    I've actually got a container of dredges here, left overs from various different 5L jugs. A couple of different brands of 5w30 synthetic and 5w30 semi-synthetic, whatever was on sale at the time, even some 10W40 there as well. It's my official top off oil and never given me any problems. :)

    All of the oils I use say that they're fully compatible with other API spec'd motor oils, I think it's part of the specification. It doesn't mean that mixing them is ideal, it's probably not, but there wont be any real problems doing it.
     
    #8 uart, Apr 9, 2012
  9. Mike500

    Mike500 Senior Member

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    Mixing in a little conventional oil doesn't hurt. Low oil level really hurts.

    But, above all, for "peace of mind," do what you need to do to achieve you own "peace of mind."
     
    #9 Mike500, Apr 9, 2012
  10. cnschult

    cnschult Active Member

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    I appreciate and respect your opinion but as I stated I have a 5Q jug of conventional Mobil "clean 5000" with less than a quart remaining that I'm trying to get rid of. I just topped off my Prius with it and I'll be topping off my Corolla later today. I'm trying to get rid of the conventional oil since I'm addicted to synthetic oil so the clean 5000 will be perfect for topping off.
     
    #10 cnschult, Apr 14, 2012
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