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  1. #11

    Join Date
    Sep 2010
    everett, massachusetts


    this is not my opinion about oil to use. GM says to use 5-30 wt oil . also you can use 10-30wt oil.

    GM states NOT TO USE 10-40 WT OIL. that means this is not to be used.

    my guess is the reason the previous owner used 40 wt is because the engine has an oil pressure issue. that usually means a worn engine / crankshaft bearing wear..

    now on my opinion about what to use with oil that is 5-30 wt mobil 1 synthetic. I use this in all my GM engines . I have no oil issues .. my 2000 5.3L uses less than 1/2 qt over 8,000miles. use pure one purolator filters [NO FRAM].engine has 150K on it .oil pressure cold start 60 psi . normal temp 40-50 psi. even @ 650 RPM in gear stopped .

  2. #12
    Jr. Mechanic
    Join Date
    Nov 2011
    Central Illinois


    Looks like the previous owner switched to 10W40 about 90k miles ago! Switching back to 5W30 or 10W30 won't hurt anything. If you notice a drop in oil pressure switch back. Any damage (and I'm not saying there was any) caused by running the 10W40 has already been done.

    I just bought an '03 Burb 2500 4x4 with 116k on the clock. Been running dino juice all of its life. It runs 38lb of oil pressure at idle, over 60lb under hard acceleration and 45lb - 50lb crusing at 65mph. Oil was changed right before I bought it. Gonna put Mobile 1 5W30 in and see how she does. ...and a Delco filter. Never use anything but a Delco filter!
    2012 Silverado 1500 LT 4X4
    2003 Suburban LT 2500 6.0L
    2004 2500HD Crew Cab LT 4x4 6.0L - SOLD

  3. #13


    Quote Originally Posted by eddie_picazo View Post
    I forgot to mention that the previous owner has been using The Mobil "High Mileage" 10W40. So keep using it with an AC Delco filter?
    Personally, I would switch back to 5w-30 if I were you, like stated above if you notice lower pressures then switch back to the other oil. Mobile 1 does make a high mileage 5w-30. The only thing about mobile's "high mileage" oils is that they are not recommended for extended idle times. This is on mobile's web site.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  4. #14


    Cool good info, I thank you guys for all the help. I will use Mobil 5w30 to 10w30 from now on.

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