Can 15W-40 Rotella T oil be used in 8.1 gas engine

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by Markd52, Sep 9, 2018.

  1. Markd52

    Markd52 New Member

    9
    May 6, 2015
    Wildwood, New Jersey
    2002 380 Sundancer
    Twin 496 (8.1) EFI Horizon inboards with V-Drives
    I have been advised that 15W-40 Rotella T diesel oil can be used in a 8.1 gas engine. Has anyone heard anything on this topic.
     
  2. rondds

    rondds Well-Known Member SILVER Sponsor

    Oct 3, 2006
    Jersey Shore
    2001 380DA
    Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
    For 9 seasons I used 15w40 in my 1989 7.4s, in spite of Merc's recommendation. Since buying this boat in 2013, I have been a good boy and followed Merc's recommendation of 25w40. I'm probably spending almost double per gallon but I'm doing it myself so there's no labor charges. Curious what others here will say about 15w40 in the 8.1.
     
    Siboatguy likes this.
  3. Siboatguy

    Siboatguy Active Member GOLD Sponsor

    226
    Mar 28, 2016
    Holmdel,NJ
    2005 Sea Ray 320 Sundancer
    Twins V-Drives
    2017 5.7 Mercruisers
    I used 15W-40 Rotella before in some of my older engines 5.7 carbs... and it was fine... These are new engines and still under warrantee so i use what they call for... The 25-40, Spent so much money on this thing why cheap out on the oil....
     
    JVM225 likes this.
  4. rondds

    rondds Well-Known Member SILVER Sponsor

    Oct 3, 2006
    Jersey Shore
    2001 380DA
    Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
    In the grand scheme of things it's not that much more money. But I wonder why Mercruiser engines are the only ones on earth that call for 25w40. Maybe b/c they (and Sierra) are the only ones that sell 25w40 oil ??

    Quick glance at Crusader's engine manual for the 2010 8.1 (and for that matter, all of the gasoline engines they sell) rec 15w40 for temps above 50*F and 5w30 for temps below 50*.

    I will continue with the 25w40 but I'd like an explanation as to why I must.
     
  5. Jimmy Buoy

    Jimmy Buoy Active Member

    Dec 3, 2008
    Sarnia, Ontario, Canada
    340 Amberjack
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    I've used Rotella 15W-40 in my 8.1's since buying it 10yrs ago without issue. I've also used it in my motorcycle engine (2006 Yamaha FJR 1300) for the last 11yrs without issue.
     
    Handsome Transom likes this.
  6. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    pa
    2018 SDX 270 OB 300 Verado
    Verado 300
    Any major brand 15w40 is a good choice for that motor, with the T4 or T5 15w40 Rotella being a very good choice.

    The new Merc oil is catalyst compatible, which means they must limit the Zinc and Phosphorous additives in it. Because of that, it is actually not as stout of an oil as the Rotella. Zn and Ph are high pressure boundary layer protection additives, and limiting them is not a great thing. I would choose the Rotella every day over the Merc oil.
     
    Handsome Transom and joeyleggz like this.
  7. juggernaut1

    juggernaut1 Active Member

    772
    Apr 19, 2015
    Perth, Western Australia
    2006 38 Sundancer
    8.1S / ZF 63V Drives
    Can't sea any problem with using the Rotella 15w/40. I've switched to aussie blended Penrite Racing 15w/50 and no longer have to top up from time to time during the season compared to when I was using the Merc 25w/40. As a plus its loaded with Zinc and Phos, contains no viscosity modifiers and claims to be shear free. Being a "light" 50, oil pressure is also similar to the 25w/40.
     
  8. Bugsy22

    Bugsy22 Member

    36
    Jun 2, 2016
    1000 islands region New York
    00' 310 Dancer w/ 5.7 EFIs and Bravo 3s. Recently purchased after having a 90' 270 Dancer for sever
    5.7 EFIs w/ Bravo 3s
    FYI, Mystic makes a synthetic blend 25w40. Its a Citgo product. Midland hardware website and the shipping isnt bad. You can buy it by the case(12 quarts) or gal jug. I had 3 quarts leftover from last fall so I ordered 2 gallons. $47 delivered. I think the case was $62 last year. No problems with it. My efis didnt burn any in 44 hours this season. I ran Amsoil in the past but it was over $110 a case.
     
  9. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    pa
    2018 SDX 270 OB 300 Verado
    Verado 300
    I ordered from Midland last year - good deal.
     
  10. LTD.330

    LTD.330 Active Member

    Oct 5, 2009
    Lake Erie
    1999 Sundancer 330
    7.4 MPI
    Another Rotella 15w-40 user in my 7.4s for the last 10 years. The stuff was made for the harsh environments diesel engines create, so plugging along in a gasser isn't an issue.
     
  11. JVM225

    JVM225 Well-Known Member

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    That’s what I did in my old boat. Rotella is great. I only switched to the Merc oil when I repowered it because of the warranty.
     
  12. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
  13. The Bill Collector

    The Bill Collector Well-Known Member SILVER Sponsor

    Jun 2, 2008
    Tacoma, WA
    450 Sundancer
    3126 Cat's
    I've got Mobil 1 5-30 full synthetic in my 8.1 Vortec
     
  14. Moondoggie

    Moondoggie New Member

    22
    Jul 6, 2018
    Central Fl.
    2018 Sea Ray SPX 210 OB
    2018 Ford F-150 Lariat
    Single Merc 150
    I use Rotella T-6 in my Honda Goldwing. A lot of other Goldwing owners have used it for and have logged over 100K on their bikes. Check the ratings for the oil and if it meets your engine specs, than use it.
     
  15. SCORPIO

    SCORPIO Well-Known Member SILVER Sponsor

    Apr 7, 2008
    Delaware
    1989 300 DA
    Twin 5.7 Merc Alpha I
    My new engines actually recommend Rotella 15/40. I've used it for 20 years in all my diesel trucks and off road equipment with no issues.
    IMO it is a great oil
     
  16. duckmnn

    duckmnn Member

    525
    Jul 21, 2010
    Grafton IL where the IL and Mississippi rivers com
    270sundancer 1996
    454 B3
    This past spring I bought rotella like I have in past. The auto store said no longer good for gassers ?? It was T4 the claim they changed formula .And I read jug . It no longer reads anything for gas. So I changed brands
     
  17. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    pa
    2018 SDX 270 OB 300 Verado
    Verado 300
    It is fine for gasoline vehicles that do not have catalytic converters. They left the zn and ph in it so it does not meet API SN as a result. It is a very good oil and great for marine engines without catalysts.
     
  18. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    pa
    2018 SDX 270 OB 300 Verado
    Verado 300
    It is fine for gasoline vehicles that do not have catalytic converters. They left the zn and ph in it so it does not meet API SN as a result. It is a very good oil and great for marine engines without catalysts.
     

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