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Help: UOA shows quite high Fuel

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by 13Plug, Jan 12, 2011.

  1. 13Plug

    13Plug Active Member

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    I got my first used oil analysis from Blackstone @ 48,000 km (roughly 30K miles). The oil has 8K km (or 5K miles). The dealer changed the oil so it's whatever they use.

    The fuel comes back at 5.3%, whereas "normal" is < 2.0%.

    Aside from that, other "unnormal" things include the Lead with a count of 9 (normal is 0), SUS viscosity is 50.9 (normal is 54-61), cSt viscosity of 7.54 (should be 8.5-10.8), and Flashpoint is 260 (should be >365).

    I don't really know what all that means... but I switched to Mobil 1 full synthetic at that change. I will not be extending the oil change interval though during the remainder of the warranty period.

    Do I have a high fuel number because I drive almost all short trips in the city. In cold wintery, snowy conditions?

    Here's the result, FYI.

    Blackstone Labs
    Equipment Make & Model: 2008 Toyota Prius
    OIL TYPE & GRADE: Dealer 5w30
    Make-up oil: 0
    OIL USE INTERVAL: 7965 km
    Miles on unit: 48000 km
    Sample Date: 12/29/2010

    Universal averages show typical wear for this type engine after about 11,800 km on the oil, so you can see how your Prius compares to others. Most metals are fine. Lead was somewhat high, and this may be due to the fuel contamination. We consider any fuel above 2.0% to be a
    possible issue, so your 5.3% is cautionary. However, since you're mostly doing short trips, fuel may be unavoidable. Fuel can cause high lead, though it could also be from a temporary particle streak. Upper-end wear is good. Watch for rising oil level on the dipstick.

    ALUMINUM 3
    CHROMIUM 0
    IRON 7
    COPPER 1
    LEAD 9
    TIN 1
    MOLYBDENUM 107
    NICKEL 0
    MANGANESE 0
    SILVER 0
    TITANIUM 0
    POTASSIUM 4
    BORON 40
    SILICON 10
    SODIUM 248
    CALCIUM 1350
    MAGNESIUM 6
    PHOSPHORUS 579
    ZINC 639
    BARIUM 1


    cSt Viscosity @ 100°C 50.9 (should be 54-61)
    SUS Viscosity @ 210°F 7.54 (should be 8.5-10.8)
    Flashpoint in °F 260 (should be >365)
    Fuel % 5.3 (should be < 2.0)
    Antifreeze % 0.0
    Water % 0.0
    Insolubles % 0.4
    TBN
    TAN
    ISO Code
     
    #1 13Plug, Jan 12, 2011
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Do you know for a fact that your engine oil was actually changed? (For example, did you look at the dipstick to see that the oil was clear after it was changed?)

    2. Yes, driving very short trips in cold weather is really bad for the engine. Maybe you should consider changing your engine oil at 3K mile intervals during the winter season.
     
    #2 Patrick Wong, Jan 12, 2011
  3. 13Plug

    13Plug Active Member

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    1. I did the most recent oil change. The oil change at 40K km was dealer, the actual 48K change was done in my garage. What I'm trying to say is the oil sample above is from the dealer 5w30 bulk oil. The oil that's *now* in the crankcase is M1. I plan on doing another UOA on the M1 either at the next oil change, or the one after that. I suspect things will look better due to the switch to full synthetic.

    2. Winter season is half the year LOL. I guess I could shorten the interval but I'd rather not. I have gone with the standard 5K mile interval up until now. I guess I'm more concerned at finding out what is the downside of such a high fuel count/percentage. It sounds bad but long-term what is the affect?

    I will likely only keep the car another 2 years (or whenever the plugin Prius comes out), so I won't have the car forever. As long as it will last 5 years total time I should be OK. Ha ha.
     
    #3 13Plug, Jan 12, 2011
  4. tochatihu

    tochatihu Senior Member

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    In the UOA report the only thing that raises a flag for me is the lead. It could be from mis-fueling as Blackstone proposes. Follow-up UOAs would aloow you to observe treands, which are the useful information.

    The viscosity and flashpoint are almost certainly linked to the fuel dilution. You could address that with different driving patterns of more frequent oil changes in the winter. Already suggested above.

    I jumped on this thread (as usual) because fuel dilution in Prius engine oil seems quite sensitive to the oil sampling procedure. If you take oil from the engine soon after startup, it will be high. If the engine is thoroughly warmed beforehand, it will probably not have high fuel in the oil.

    Yours is a young car so we would set aside the possibility that the PCV valve is not working well.

    The reason they suggest to watch for rising oil level on the dipstick is because that is what would happen if the oil is chronically being diluted by fuel.
     
    #4 tochatihu, Jan 12, 2011
  5. uart

    uart Senior Member

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    Hi Swanny. Apart from the high fuel dilution the results look pretty good. All wear metals except lead are very low. The lead in bearing metal is usually accompanied by either tin or copper, so the very low reading on these two means that there probably isn't really any issue with the bearings either (also 9 ppm is not all that high for lead anyway).

    Re the fuel dilution YES it's totally related to the short trips and cold weather. All engines have some small amount of fuel that gets past the rings and into the crank case (oil). This is totally normal. What should happen however is that as soon as the oil is fully warmed up (around 180F or more) that the fuel vaporizes off and is actually recycled (reburnt) via the crankcase ventilation system.

    So fuel dilution is NOT strictly a cumulative process. For example it's possible to have less fuel dilution at 6000 miles than you had at 5000 miles! All you have to do is go for a long drive where the engine gets fully up to temperature and where the ICE remains running for a sustained period of time.

    The fact that the Pruis ICE doesn't always run continuously does seem to make it more likely that the oil wont reach sufficient temperature for this mechanism to work the way it's supposed to. If you seldom do enough sustained driving to keep the ICE nice and hot then yeah the best thing for it is short oil change intervals.
     
    #5 uart, Jan 12, 2011
  6. triumph1

    triumph1 Member

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    Gray bottle, blue label from BJs Warehouse.

    Miles on oil : 10,500
    Miles on Unit: 62,500
    Filter Mobil 1
    Grade 5w-30

    "Check for source of FUEL LEAK (injectors, lines etc:). Fuel is at a SIGNIFICANT LEVEL; FUEL DILUTION has caused viscosity to decrease slightly below
    grade; Total Base Number is MODERATELY LOW; Infrared results indicate that NITRATION is at a MODERATE LEVEL;
    (PRODUCT NAME); Lubricant and filter change acknowledged; Resample at half interval;"


    Nitrate 23
    Oxida 15
    TBN 2.7
    Visc @ 100c 9.0
    Water <.1
    Soot <.1
    Fuel 4.4
    Zinc 680
    Phosphorous 581
    Calcium 1970
    Magnesium 8
    Boron 6
    Molybdenum 52
    Sodium 3
    Silicon 16
    Copper 1
    Aluminum 3
    Iron 1

    The high fuel may be because when I changed the oil this last time, I think I just let it idle for 5-10 mins, then drove it for like 1 minute around the block. My first UOA I did at 17k, (a 15k OCI), the fuel was at 3.3%, then the next three UOAs came back way lower, at 1% or less.
     
    #6 triumph1, Jan 12, 2011
  7. cwerdna

    cwerdna Senior Member

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    I had my 1st UOA done at 49,519 miles and Blackstone also commented that fuel dilution was high.
    Their words:
    I did mention to them when mailing out my sample that my car was moved at least once by the dealer, after dropoff, which should've started the ICE.

    My reply was
    Their reply was:
    I'll have to do that next time.
     
    #7 cwerdna, Jan 12, 2011
  8. 13Plug

    13Plug Active Member

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    OK, well I would say around 90% of my driving is city driving. Mostly but not all are short trips as well. Is it safe to say that the fuel in the oil is more likely there because the engine is not warmed up and in "closed" loop mode?

    I do some highway trips. I should make a point of doing a 20-min long highway trip before the oil change / oil sample? I could make a point of making a longer-ish trip one or two times per month during the cold weather if it will help.

    I'll be interested to see if the Mobil 1 or warmer weather help this situation. My next oil change is scheduled for the end of June, or 56K km. I was going to skip the UOA on the next change, but now I think I should do another just to see if the fuel number goes down. The weather here will be nice and warm so I anticipate the fuel number will be lower in part because of that.

    It's kind of a trade-off. I don't want to change the oil earlier than recommended unless it is damaging the engine (wasteful). And I don't want to make frequent highway trips just to burn off the fuel (again, wasteful).
     
    #8 13Plug, Jan 12, 2011
  9. uart

    uart Senior Member

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    I don't think Mobil One will have any effect on fuel dilution over the dealer bulk oil you were using.
     
    #9 uart, Jan 13, 2011
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