Mobil Super High Mileage 5W-30
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  • 1 Post By stoveguyy
Cadillac Seville / Cadillac Eldorado Forum Discussion, Mobil Super High Mileage 5W-30 in Past Cadillac Vehicle Discussion; Just wanted to know the experts opinion if this oil is safe to use on my car and won't cause ...
  1. #1
    Amir A's Avatar
    Amir A is offline Cadillac Owners Member
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    Mobil Super High Mileage 5W-30

    Just wanted to know the experts opinion if this oil is safe to use on my car and won't cause problems later on. thank you.

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    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Definitely safe, but there's no real advantage to it over any other semi synthetic oil (which your engine doesn't require anyway). It will not stop or prevent leaks, and change intervals remain the same - follow your OLM.

    Use whatever oil you'd like, as long as it's the correct viscosity.

  4. #3
    drewsdeville is offline Cadillac Owners Master
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    Re: Mobil Super High Mileage 5W-30

    If it is the manufacturers specified weight, then yes, it is safe.

    That is all.

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    Re: Mobil Super High Mileage 5W-30

    Which engine/car ??? 5W-30 is the specified oil for the later GM Northstar. It's in the owner's manual.

    Begs the question: Is there some reason that you think a "high mileage" oil is necessary ? (or does the name just sound warm and fuzzy ?)

  6. #5
    basscatt's Avatar
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    Re: Mobil Super High Mileage 5W-30

    is it SAFE to use - sure -

    will it BENEFIT your car over regular plain old 5w30 oil - NO

  7. #6
    stoveguyy is offline Cadillac Owners Connoisseur
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    Is it for cars with "super high miles" or is it "super" oil for high mileage cars?
    eldorado_97 likes this.

  8. #7
    Amir A's Avatar
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    Re: Mobil Super High Mileage 5W-30

    Sub, My 03 Seville. it has 115,000 miles on it. and I have some oil leaks.

  9. #8
    basscatt's Avatar
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    Re: Mobil Super High Mileage 5W-30

    Quote Originally Posted by Amir A View Post
    Sub, My 03 Seville. it has 115,000 miles on it. and I have some oil leaks.
    ------------------------
    if you are HOPING it will reduce the oil leaking - it will not -

    as I said - you will see no benefit over any other conventional oil -

  10. #9
    Chuckj19's Avatar
    Chuckj19 is offline Cadillac Owners Member
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    Had a oil leak on a 99 sts..use whole quart of lucas oil stabilizer and 6 quarts of oil and my leak and consumption has decreased dramatically..remember not to overfill.your northstar only needs 7 quarts total

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    MoistCabbage's Avatar
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    Capacity is 7.5 quarts total.

    GM specifically recommends NOT using additives. All the Lucas does is thicken the oil slightly, the leak is slowed slightly.

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    Submariner409's Avatar
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    Re: Mobil Super High Mileage 5W-30

    I would not put that "oil stabilizer" in a blown up Briggs&Stratton lawnmower engine, much less a Northstar.

    For oils and additives, read the GM recommendations in your owner's manual (GM, Ford, MB, Toyota, Jaguar etc., etc., etc.) might have some, small, foggy idea of what's best for their various engines.)

    If the rows and rows of snake oils and magic potions that line the parts store shelves are so wonderful, why don't the world's auto manufacturers use them in the first place ???

    I have worked at many an auto parts store, both full and part time, off and on, over the past 57 years - not because I needed the money; rather, the discounts on parts are significant. For some insider info, Google "spiff".

  13. #12
    Chuckj19's Avatar
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    These guys know best OP..I was strapped for cash at the time, thats why I used the Lucas..but Ive heard of leaks and consumption at 8 quarts and at 7-7.5: no problems?

  14. #13
    Submariner409's Avatar
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    Re: Mobil Super High Mileage 5W-30

    Unfortunate fact is that some of these Northstars develop oil leaks - at the oil pan line, halfcase seal line, the cam cover seals and at the rear main bearing seal. Using thicker oils and sealers is only a temporary BandAid. As with coolant, transmission, P/S or brake fluid leaks the only correct "fix" is diagnosis and mechanical repair......... and in our cars, for engine oil leaks, that isn't cheap by any stretch of the imagination.

    The easiest of the common oil leak points to fix is the oil filter adapter block seal(s) and the oil pressure sending switch.

    The articles way up ^^^ in Cadillac Technical Archive (top black bar) discuss Northstars, engine oil, proper fill levels, and excessive oil consumption. Yes, some Northstars burn oil (yet another mechanical fault) but that can be exacerbated by overfilling the engine. The correct level - from the GM manuals ad CF advice - is 7.5 quarts including filter. Dumping in 8 quarts may increase perceived oil consumption rates - until the level drops to the correct amount.

    The engines do not use "gaskets" as such - the engine joint flanges are precision machined and form a single unit "block" - so the joints are sealed with formed silicone "O-ring" type seals set into machined grooves. The current seal repair is to clean everything (engine disassembly required) and use the new GM/Permatex UltraGray RTV sealant in a sized bead in the original seal grooves. The lower engine case is actually a 4-bolt-main bearing cap girdle as well as a very effective windage tray, so it is a load-bearing engine part; the oil pan is also a structural part of the engine - it doesn't simply hang there.

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