Did my oil change affect my MPG?

Discussion in 'Gen 2 Prius Fuel Economy' started by Toyotally04, Aug 14, 2020.

  1. Toyotally04

    Toyotally04 Junior Member

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    So when I got my 2004 Prius, the previous owner went to Toyota Dealership for oil change. (0w20 grade)

    Last June, I went to a local franchise. (5w30)


    Since then, my gas mileage seemed to drop significantly.

    Whenever I had oil changes on my previous cars, gas mileage usually improved for the first one or two fuel-up.

    Am I missing something here?

    TTLLY04

    Re:
    Another thread, another oil change... | PriusChat

    So I finally got my 1st oil change, but... | PriusChat


    Screenshot_20200814-192015.jpg
     
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    Probably wouldn't hurt to check level to verify it wasn't significantly overfilled...happens fairly often.
     
  3. Toyotally04

    Toyotally04 Junior Member

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    Hmm... would it matter? The oil was changed 2 months ago.
     
  4. oldtechaa

    oldtechaa Active Member

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    I believe many have found that if the oil is overfilled the crank slaps it, foaming it and causing a number of problems, including poor fuel economy.
     
  5. lovepitbulls

    lovepitbulls Junior Member

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    thicker oil maybe?
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    You switched to a slightly thicker oil (the spec'd oil, btw). It will be a factor, not sure how much.

    "local franchise" is Toyota dealership, quicky lube place?
     
  7. Toyotally04

    Toyotally04 Junior Member

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    Yeah.. But quick change place...
     
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  8. Toyotally04

    Toyotally04 Junior Member

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    Another question/ something to consider:

    So. Cal. has been unbelievably hot lately.

    100°F everyday for almost 10 days. Dry baking heat, not the humid sweaty summer.
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    Assume you're using AC then?
     
  10. Toyotally04

    Toyotally04 Junior Member

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    Yeeeah....
     
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  11. Toyotally04

    Toyotally04 Junior Member

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    So, my follow up questions would be:

    1. Am I using the right oil grade for 100℉ summer weather?

    2. If my crank is overfilled, is it too late for mechanic to check the damage? How severe would it be?

    TTLLY04
     
  12. oldtechaa

    oldtechaa Active Member

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    I would say it doesn't look unreasonable for a hot summer with AC use, a thicker oil, and possible crankcase oil slap. If it is overfilled, it's not really damaging anything, although I believe the crankcase slap can cause some cavitation which theoretically far down the road could cause metal wear, but that's not really something to worry about. The main issue is just if it is still overfilled, it will continue lowering your fuel economy. All that would need to be done is remove some of the oil, either by using a syringe down the dipstick tube or by loosening the drain plug and letting about 2/5 qt drain out.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    Check the oil level first, resolve whether or not its overfilled? I suspect it's not, but let's check.
     
  14. Kenny94945

    Kenny94945 Active Member

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    Yes, first step check the oil level.
    Yet OP mentions significant drop.

    AC use and tire pressures would be my thoughts.

    Yet, going further maybe brake drag?
    Maybe less efficient brand of fuel or winter to summer fuel formula changes.
    Dirty air filter or intake leak or not running on all cylinders? (Quick Lube mistakes)
    20 weight vs 30 weight hot....maybe but I would not have thought significant mpg loss.
    0 vs 5 is for cold again, I would not have thought significant mpg loss.

    Let us know what you find.
     
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  15. Toyotally04

    Toyotally04 Junior Member

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    So referring to the 2nd link from my starting post in this thread:

    I realized that the service invoice indicated 5 quarts were filled.

    A mechanic wouldn't be that oblivious to do that, would they? ... Wouldn't it be a more "business-minded" attitude to have conveniently/innocuously "overcharge" for filling less oil than recorded?

    ...

    Secondly, somewhere in one of the threads I made, someone mentioned "paying under the table" for bringing your own oil, filter, and bolt. Can I do that at a franchise, like Jiffy Lube. Or do such businesses keep strict documentation and records.

    ...

    Lastly, my oil dipstick is heavily stained.

    ...

    I'm due for another oil change this month.

    TTLLY04
     
  16. Toyotally04

    Toyotally04 Junior Member

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    Ah um.... Upon closer examination of my service invoice, I find that the franchise service operators used FRAM OIL FILTERS.

    I searched the words according to their parts inventory ID: FLTPG4476

    So how likely would an below-average oil filter affect a palpable drop in gas mileage?
     
  17. oldtechaa

    oldtechaa Active Member

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    That wouldn't be a factor. There's nothing about a Fram oil filter that would affect gas mileage.
     
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  18. edthefox5

    edthefox5 Senior Member

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    Your very fixated on the oil over many posts.

    Dealer oil changed all its life it has seen some god awful cheap oil and has been routinely overfilled. That's why the dipstick looked so bad
    in your other posts. Really crappy oil.

    Throw the dealers the keys and say change it you get the vat oil. But usually some donuts.

    Mileage is bad because unless the hybrid battery has been replaced its way way way overdue to be replaced. This forum has hundreds of posts about failed or failing hybrid battery and how to service them. Start reading your going to need it.

    The cars power comes from the hybrid battery. Poor mileage because you have to push the gas pedal more and more to get the car going because the hybrid battery is contributing less and less propulsion power.

    Go to toyota.com/owners forum and join. Have your insurance card handy as they will ask for the vin.
    Once joined go to the service forum and you will see every instance that car has had service at an authorized Toyota dealer.

    You may see why it was sold or traded in.

    Start watching the battery monitor screen on the mfd for the battery's behavior. Note how many times it goes to one purple bar and how fast it will go from a good 2 blue bars to a bad one purple bar. How often the engine comes on when its sitting. If your sitting and the engine is running that means the battery needs a charge. Not good.

    Lots of purple bars or worse no bars just white screen is very aged battery.

    Howe much did you pay for the car?
     
  19. edthefox5

    edthefox5 Senior Member

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    Oh and Jiffys database shows the Prius G2 takes 5 quarts.

    Its takes exactly 3.9 quarts with new empty oil filter so your a quart over filled. I have changed the oil on my g2 maybe 30 times.

    Nothing under the table about bringing your own oil I used to do it all the time at Jiffy they don't care.
    Go online look for a coupon and bring them 4 quarts of oil and a new filter. Mine charges $20. labor. I don't let them touch anything else. I stand there and watch them.
    When I give the guy under the car changing the filter I duke him $5 and tell him not to go crazy on the pan bolt please.

    But your only going to bring your own oil if its better then what they have in your case just have them put cheap 5-30 oil in it. I'm pretty sure your engine eats oil bad.
    Synthetic is a waste of money at this point. Just tell them to put 4 quarts in it.

    Haven't been to Jiffy in a long time since found a good shop that likes cash. They let me under the car when they work on it. All you got to do is duke 'em. They see me coming and wave me right in lol....

    You really need to see whats under the car. How rusted it is. Whats leaking. Whats just dried up ready to fall off. Especially a 16 year old car.

    if you ever get a chance to get under the car on a lift take alot of pictures of everything under there with your phone.
     
    #19 edthefox5, Sep 6, 2020
    Last edited: Sep 6, 2020
  20. Toyotally04

    Toyotally04 Junior Member

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    Yeah, I kinda freaked out months ago, when I learned the possibility that mechanics might overfill a customer's engine.

    Then, when my gas mileage dropped from 45mpg to 38 during these past few months, I got really concerned.

    I never had a problem with drop in gas mileage with my previous 1999 Accord and 2005 Corolla (all used, of course). When those cars left my usual quick oil change shop, the gas mileage usually improved quite a bit.

    TTLLY04

    (also, the car has always been kept within the extended family. first, my cousin's then gf now wife, to my cousin, my brother, now me.)
     
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