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Engine oil - is mixing types an issue?

  • 04-06-2009 6:43pm
    #1
    FedFrank2
    Registered Users Posts: 230 ✭✭


    I recently bought a car second hand (04 Audi A4 1.8T petrol), and just when doing my regular checks I noticed the oil level was down slightly, not to the min level or anything, but I would like to top it up.

    I'm not sure if the oil that is currently in it is semi synthetic or mineral based (btw, which of these is 5w-40 and 10w-40?).

    If it is semi synthetic currently in the engine, would there be an issue if I topped it up with mineral based, and vice versa, or would I need to top it up with the same type of oil?


Comments

  • #2
    Captain Slow IRL
    Registered Users, Registered Users 2 Posts: 3,651 ✭✭✭Captain Slow IRL


    You shouldn't mix semi with fully synthetic. The viscosity should also be the same - 5w30, 10w40, etc. Check here (click!) to see which grade of oil you should use.

    For peace of mind, you should either ask the seller what grade oil went into it or just change it yourself so you'll know for future.


  • #3
    Heroditas
    Registered Users, Registered Users 2 Posts: 9,558 ✭✭✭Heroditas


    FedFrank2 wrote: »
    I recently bought a car second hand (04 Audi A4 1.8T petrol), and just when doing my regular checks I noticed the oil level was down slightly, not to the min level or anything, but I would like to top it up.

    I'm not sure if the oil that is currently in it is semi synthetic or mineral based (btw, which of these is 5w-40 and 10w-40?).

    If it is semi synthetic currently in the engine, would there be an issue if I topped it up with mineral based, and vice versa, or would I need to top it up with the same type of oil?


    Good God, I hope you don't have semi-synthetic in your car.
    Your car should be using fully synthetic long-life oil.
    I had major problems earlier in the year with my 2003 1.8T because it turned out that the previous owner had appeared to use semi-synthetic. As a result, the gauze for the filter got blocked up with carbon from the semi-synthetic getting "burnt" and I had major oil pressure issues nearly resulting in the engine seizing. I had to get the sump dropped out of the car and the gauze cleaned out - an expensive job when they also had to throw in a few more litres of oil.


  • #4
    Neilw
    Registered Users, Registered Users 2 Posts: 3,788 ✭✭✭Neilw


    Fully synthetic is the way to go, I use 5w40 and change every 6k miles. Small sump in the 1.8t A4's so have a smaller oil capacity. Regular changes with fully synthetic oil will reduce the chance of the oil pickup getting blocked.

    As a precaution I'm getting an oil pressure test done on my car to see if the oil pickup is anyway blocked. VW spec is 3 Bar minimum @ 2000rpm but a clean engine with a healthy oil pump will make over 4Bar once nothing is blocked.


  • #5
    L1011
    Registered Users, Registered Users 2 Posts: 69,592 ✭✭✭✭L1011


    Captain Slow IRL wrote: »
    You shouldn't mix semi with fully synthetic. The viscosity should also be the same - 5w30, 10w40, etc. Check here (click!) to see which grade of oil you should use.

    That site has two types recommened for my car, 0w30 and 10w40.

    The manufacturer recommendation is 5w40... even Halfords manage to get that one right on their in store flip charts (and also recommend 0w30 as a "performance" option).


  • #6
    Captain Slow IRL
    Registered Users, Registered Users 2 Posts: 3,651 ✭✭✭Captain Slow IRL


    MYOB wrote: »
    That site has two types recommened for my car, 0w30 and 10w40.

    The manufacturer recommendation is 5w40... even Halfords manage to get that one right on their in store flip charts (and also recommend 0w30 as a "performance" option).
    Q. How do you tell if a VW is fixed or variable servicing?
    A. On the vehicle data carrier plate of the car will be the letters “QG1” or “QG0/2” – the QG1 refers to the engines on variable or “Longlife” servicing and these cars will use the EDGE 5W-30 The letters QG0/2 indicate fixed servicing and these cars will use the EDGE 0W-30.

    PD (Pumpe Duese) diesel engines on fixed servicing will use the EDGE 5W-40 (505.01 specification)

    Most recent VW and Audi cars (from 2000 onwards) are on the variable servicing schedule.

    source

    I'm not sure if the above statement is applicable to your car.


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