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  1. #1
    Seaman
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    Question can I put diesel oil in my engine ?

    good day,

    1980 Mercruiser MCM 898 (305) V8 s/n 5452697
    I was told yesterday by a mecanic tech that I can put 15w40 diesel oil in my engine because it's old and diesel oil will better lubricate the engine. He recommended SHELL diesel oil.
    Does it make any sense ?

    Louis

  2. #2
    Moderator Bondo's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Ayuh,..... You can if you want too.....

    Diesel oils are basically the same oils, with a higher detergent package.....

    It comes down to my signature,.... Just change the word Grease to Oil......
    Any Grease is Better,..... Than No Grease at All.......

  3. #3
    Admiral ziggy's Avatar
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    Default Re: can I put diesel oil in my engine ?

    theres been quite a few oil threads here on the fourm. use the search function to find a lot of info and opinions.... my opinion is i don't know which oil to use for being the best. however i feel that mercuriser probably knows what they think is best for mercruisers..... so, since i have a mercruiser, even though it is old like yours.... i use mercruiser oil... 25W-40.....
    'Lime Time'
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    Mercruiser 165hp (chevy 250 L6), MC-1 drive

  4. #4
    Chief Petty Officer Mkos1980's Avatar
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    Default Re: can I put diesel oil in my engine ?

    I run Shell Rotella with no problems. I think it has a higher zinc? content which helps with the lifters vs todays newer roller lifters which dont need it
    90 Chaparral 2150SX 350 MAG Alpha 1
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  5. #5
    Rear Admiral JustJason's Avatar
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    Default Re: can I put diesel oil in my engine ?

    if your in canada you may want something with a lower base stock. Maybe 10-30 or 10-40.
    I have and old boat and i run straight 30HD. And i make sure i let it warm up every time before I take it out.

    Nothing wrong with running an oil in the 40 and even 50 weights. as long as its not 0 degrees when you start it, and as long as you make sure it warms up first.
    just because you found it that way... doesn't mean it's supposed to be that way.

    Part of diagnostics is spending time figuring out not only what the problem is, but also sorting through what it isn't.

    The older the engine is, the chances of it having more than 1 problem goes up exponentially

    Boating has always been a rich mans hobby. Buying a new boat gets cheaper every year, but the maintenance, the repairs, and the overall cost of ownership of a boat has never gotten any cheaper.

  6. #6
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    Default Re: can I put diesel oil in my engine ?

    [....
    Last edited by whywhyzed; May 24th, 2008 at 05:17 PM.

  7. #7
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    Default Re: can I put diesel oil in my engine ?

    Diesel oil is rated for both C and S engines, which means it is suitable for compression and spark ignition engines (gas and diesel). It basically comes down to the correct viscosity. 15W40 sounds good. Try it and see how it works.

    Have a great day,

    Rob.

  8. #8
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    No problem, I use it in my 350..

  9. #9
    Fleet Admiral HT32BSX115's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Hey!!! another oil thread!!!! We never have those......



    Yeah you can use it (I use Shell Rotella 15W40 in mine)


    (Although C & S have never meant compression and spark....it's a rough equivalence )



    Just change it once a year...preferably right after your last run of the season.......your engine will never know the difference!





    Quote Originally Posted by Robj View Post
    Diesel oil is rated for both C and S engines, which means it is suitable for compression and spark ignition engines (gas and diesel). It basically comes down to the correct viscosity. 15W40 sounds good. Try it and see how it works.

    Have a great day,

    Rob.
    73 de Rick
    ----------------------------------------------------------------------------------
    I use xxx oil and have never had a problem........
    1987 FourWinns 211 Liberator, 7.4L- Bravo III installed by ME,
    Formerly OMG 460 King Kobra powered
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    , Franklin 6A-335B. Hartzell CS 2-blade prop
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    All PM's cheerfully answered! Please ask tech questions in the appropriate forum so everyone's included

  10. #10
    Admiral tommays's Avatar
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    Default Re: can I put diesel oil in my engine ?

    WELL

    Auto oils have had the ZDDP level reduced to meet current EPA requirments


    "Most" true diesel oils should still there full dose of ZDDP (which is a good thing )


    Flat tappet cams like the ZDDP


    Tommays

  11. #11
    Seaman
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    Thumbs up Re: can I put diesel oil in my engine ?

    thanks for your replies and help.
    I change engine oil one a year, I will try the Shell Rotella 15w40 this time.
    I appreciate.
    Louis

  12. #12
    Moderator QC's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Here's the straight skinny on API Oil ratings. I was taught Compression and Spark as well, but it is Service and Commercial . . . I was also taught that when two ratings are given, such as CJ-4/SM, then the first one was the intended rating and the second was met based on the composition kinda by accident. Anyway, the chart explains it all . . .

  13. #13
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    Default Re: can I put diesel oil in my engine ?

    If I would have put commercial and service, most people would not know what I am talking about.........including myself. Spark and Compression is how I remember the difference.

    Have a great day,

    Rob.

  14. #14
    Fleet Admiral HT32BSX115's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Oh...gawd! This thread ought'a be good for at least 100 posts!!!


    Yes ZDDP (and diesel oils) is good for flat tappet engines....I'm also using it in my old Ford Y-block!

    Unfortunately ZDDP coming out of all the oils, even the diesel oils, since it interferes with the cat converters and the after treatment systems in the newest diesels.

    I haven't had a close look at the latest NMMA FC-W oil make up but I would be willing to bet that it will be the last oil to have a suitable level of ZDDP until marine (4-stroke) engines are forced to use cat converters (2 years maybe?)

    Most new marine engines are probably not going to have problems since most are "roller-follower" engines anyway...

    We'll all probably have to switch to Aeroshell 15W50 to continue to get the high levels of zddp or start using some snake oil additive sold at high price over the counter! (illegal in California of course!!)

    The EPA is really beginning pizz me off!!!








    Quote Originally Posted by tommays View Post
    WELL

    Auto oils have had the ZDDP level reduced to meet current EPA requirments


    "Most" true diesel oils should still there full dose of ZDDP (which is a good thing )


    Flat tappet cams like the ZDDP


    Tommays
    73 de Rick
    ----------------------------------------------------------------------------------
    I use xxx oil and have never had a problem........
    1987 FourWinns 211 Liberator, 7.4L- Bravo III installed by ME,
    Formerly OMG 460 King Kobra powered
    1947 Stinson 108-2 Station Wagon
    , Franklin 6A-335B. Hartzell CS 2-blade prop
    -
    All PM's cheerfully answered! Please ask tech questions in the appropriate forum so everyone's included

  15. #15
    Petty Officer 3rd Class 96lt4c4's Avatar
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    Default Re: can I put diesel oil in my engine ?

    If you have a roller cam then you can run whatever you want. I was running Shell Rotella with the factory flat tappet. Now I am going to 5w 30 since I have installed the LT4 roller cam.

    I have been hearing rumors that the ZDDP additive is on its way out of the Shell oil as well. My dad keeps tabs on it because of his Cuda.

    Comp cams makes a cam break in additive that you can run with regular oil that has lower levels of ZDDP.
    -1990 Glastron 5.0 Alpha 1
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  16. #16
    Moderator achris's Avatar
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    Default Re: can I put diesel oil in my engine ?

    I use Fuchs 'Titan ultralube 15W40', because I have a petrol sterndrive and a diesel Landcruiser and want to use one oil for everything. Did a lot of reading before I made any decisions and concluded that the diesel oil was designed for high and continuous loads and was less likely to breakdown as quick as the oil designed solely for petrols.

    Try this website, it has all you need to know....

    'http://motorcycleinfo.calsci.com/Oils1.html

    Chris..........
    The world takes on a whole new perspective when viewed from 100' below...



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  17. #17

    Default Re: can I put diesel oil in my engine ?

    Well there! haha! I was wondering do they have a straight 30w diesel oil? I have an old motor too and i like the regular straight 30 but being their removing the zinc, if they have a diesel straight 30 is what i may try?

  18. #18
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Quote Originally Posted by starsnstripers View Post
    Well there! haha! I was wondering do they have a straight 30w diesel oil? I have an old motor too and i like the regular straight 30 but being their removing the zinc, if they have a diesel straight 30 is what i may try?
    Look for Rotella in straight 40wt..its out there..

  19. #19
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Quote Originally Posted by 96lt4c4 View Post
    I have been hearing rumors that the ZDDP additive is on its way out of the Shell oil as well. .
    Its on the way out of everything soon (the "cat" thing). BUT, you CAN buy it as an additive in 6oz bottles or something like that. Looked into it last year, after reading a good article in Hot Rod..I'll see if I can find more on it..

  20. #20
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Google ZDDPlus.com
    Also Summit Racing sells a Bottle of Cam Break-in stuff, Made by Crane...
    "Crane Super lube Break-in Concentrate"
    Just use it every oil change..
    GM used to sell good stuff, but the EPA nailed them on it too

  21. #21

    Default Re: can I put diesel oil in my engine ?

    I wanted 30w?

  22. #22
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Quote Originally Posted by starsnstripers View Post
    I wanted 30w?
    Far as I know its 15-40, or 40..no 30wt

  23. #23
    Vice Admiral Scaaty's Avatar
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    Default Re: can I put diesel oil in my engine ?

    Guy on ebay sells ZDDP, and sells a lot..
    http://cgi.ebay.com/ebaymotors/ws/eB...44226&Category=

  24. #24
    Chief Petty Officer Caveman Charlie's Avatar
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    Default Re: can I put diesel oil in my engine ?

    They make a straight 30W oil for older diesel engines. We used to use it in our tractors on the farm years ago. But, everything made after the early 80's calls for 15w40.

  25. #25
    Chief Petty Officer Caveman Charlie's Avatar
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    Default Re: can I put diesel oil in my engine ?

    I bought my boat last fall and only had the chance to get it in the water a few times. I see in the book now that my 74 Mercruiser 140 calls for 30w MS or SD oil. I'll probley use the old 30w diesel oil we still have left on the farm.

    Now if only I can figure out how to drain the old oil.

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