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  1. #1
    Join Date
    Oct 2007
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    MK
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    Default Cat 3126ta engine oil

    Hi

    I am about to buy a boat with Cat 3126's, I am aware of the issues and have been in touch with Cat whom informed me the 6MK... models were later and did not suffer from some of the issues of the earlier engines.

    I could do with some advice on oil selection. As many of you know, CAT/Finnings recommend their monograde oil 30W. I will of course use 30W but wondered what others are using in their Cats?

    Someone from this parish has already recommended Exol Taurus 30, which to me seems perfectly fit for purpose, but are there other good quality oils I might use that others have used successfully. The 3116 and 3126 both use this Spec oil. Any advice/guidance welcome.
    Last edited by John100156; 17-08-19 at 10:01. Reason: typo
    PRINCESS 45

  2. #2
    Join Date
    Mar 2002
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    17,489

    Default Re: Cat 3126ta engine oil

    Quote Originally Posted by John100156 View Post
    CAT/Finnings recommend their monograde oil 30W.
    I will of course use 30W but wondered what others are using in their Cats?
    The official Cat recommendation is more tricky than that.
    Aside from the fact that they specify either SAE 30 or 40 (and I'd rather go for 40 in the Med, though I suppose Finnings suggestion of 30 is more appropriate for the UK), they actually specify "their" so called Special Application Engine Oil, aka SAEO.
    This is supposedly formulated to minimize the formation of deposits on the turbo and aftercooler, caused by the crankcase blowby recirculation.

    FYI, it's also possible to route this blowby elsewhere than in the turbo inlet, in which case Cat specifically recommends their multigrade oil instead, so it's pretty obvious that for the engine as such, multigrade is better than monograde (particularly in cold climates, I suppose).
    Otoh, I only came across one 3116 (single, 205hp, A-rated) powered workboat where the crankcase blowby had been re-routed.
    Sorry, I can't remember how exactly, but I guess a Cat dealer could assist, if you wish to consider that.
    I never found such modification on any 31x6 powered pleasure boats I've seen, but I would have investigated that further, if it weren't that I discovered this possibility only a few years ago, when I had already decided to sell my old 3116 powered boat.

    Back to the point, yes, according to Cat you should use (in a standard 31x6 installation) either SAE 30 or 40, but if you don't use "their" SAEO, your turbos/CACs might over time cumulate harmful deposits anyway.

    All the above is as far as theory goes.
    In practice, what I always used in a 3116 powered boat that I owned for 17 years, clocking 1500 hours or so, is the multigrade Mobil Delvac MX 15W-40.
    And having still cruised on her for a few hours not later than yesterday, I can confirm that her engines are still is BY FAR the ones with the cleanest oil and exhaust I ever came across. I wish my current MANs were half as good, in this respect.
    Besides, the last time I removed the air filters (a couple of years ago, together with the new owner), the turbo blades were clean enough to eat out of them.
    Mind, that's a full displacement boat, where the engines spent 99.9% of their life anywhere between 1400 and 1700rpm, burning 8 to 10 lph each, with a load so low that according to Portofino the engines should be thrown away by now...
    Therefore, in a more "normal" planing boat installation, I suppose that YMMV.

  3. #3
    Join Date
    Apr 2011
    Location
    Boat- Western Med
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    5,206

    Default Re: Cat 3126ta engine oil

    [QUOTE=MapisM;6878974
    And having still cruised on her for a few hours not later than yesterday, I can confirm that her engines are still is BY FAR the ones with the cleanest oil and exhaust I ever came across. I wish my current MANs were half as good, in this respect.
    Besides, the last time I removed the air filters (a couple of years ago, together with the new owner), the turbo blades were clean enough to eat out of them.
    Mind, that's a full displacement boat, where the engines spent 99.9% of their life anywhere between 1400 and 1700rpm, burning 8 to 10 lph each, with a load so low that according to Portofino the engines should be thrown away by now...
    Therefore, in a more "normal" planing boat installation, I suppose that YMMV.[/QUOTE]

    Apples and oranges re load rating .
    My planning boat MAN engines ( like yours now ) run at 58 % Load @ 9.3 knots with 860 rpm and 0.1 bar turbo .
    So your old D speeder would be well up there load wise in the rev range you quote above , that’s why it was un troublesome .
    Oil blackening thing -
    There’s a school of thought that if it’s black or soon becomes black after a lub change it actually doing its stuff carrying in suspension the very harmful #hit it’s designed to do .
    It’s the still honey coloured ( or whatever) after a season thats what you should worry about !

  4. #4
    Join Date
    Mar 2002
    Posts
    17,489

    Default Re: Cat 3126ta engine oil

    Quote Originally Posted by Portofino View Post
    My planning boat MAN engines ( like yours now ) run at 58 % Load @ 9.3 knots with 860 rpm and 0.1 bar turbo.
    So your old D speeder would be well up there load wise in the rev range you quote above
    No way, Porto.
    I sort of regret having mentioned your view on diesel engines load (which ain't only yours, admittedly), but all I meant was that my first hand experience is very different, nothing else.
    Obviously I didn't have any electronic malarky on the old lady, but I did make some math based on Cat curves.
    Let's consider my preferred rpm/speed (around 8.5kts at 1600rpm).
    Based on Cat prop demand curves, I should have used 65hp out of the 153 that the engine can produce at full load, i.e. 42%.
    BUT, again based on Cat prop demand curves, I should have burned 13.4 litres each side, while in reality the boat only sipped 8 to 9.
    So, my estimate based on reverse calculation is that the boat was actually happy with just 40hp each side, i.e. 26% of the max 3116 output at full load.
    Which makes perfect sense if you think about it, because the prop demand curves are simply an average estimate, while each hull is more/less efficient at any speed, and obviously my old one was VERY efficient in the 8 to 9kts ballpark.

    Btw, 9.3kts strikes me as a very inefficient speed for your boat, instead.
    In fact, I bet that you are burning much more than 16/18 lph TOTAL at that speed, in spite of the fact that the weigh is (I guess) one third or so, compared to my old lady.

  5. #5
    Join Date
    Apr 2011
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    Boat- Western Med
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    5,206

    Default Re: Cat 3126ta engine oil

    Quote Originally Posted by MapisM View Post
    No way, Porto.
    I sort of regret having mentioned your view on diesel engines load (which ain't only yours, admittedly), but all I meant was that my first hand experience is very different, nothing else.
    Obviously I didn't have any electronic malarky on the old lady, but I did make some math based on Cat curves.
    Let's consider my preferred rpm/speed (around 8.5kts at 1600rpm).
    Based on Cat prop demand curves, I should have used 65hp out of the 153 that the engine can produce at full load, i.e. 42%.
    BUT, again based on Cat prop demand curves, I should have burned 13.4 litres each side, while in reality the boat only sipped 8 to 9.
    So, my estimate based on reverse calculation is that the boat was actually happy with just 40hp each side, i.e. 26% of the max 3116 output at full load.
    Which makes perfect sense if you think about it, because the prop demand curves are simply an average estimate, while each hull is more/less efficient at any speed, and obviously my old one was VERY efficient in the 8 to 9kts ballpark.

    Btw, 9.3kts strikes me as a very inefficient speed for your boat, instead.
    In fact, I bet that you are burning much more than 16/18 lph TOTAL at that speed, in spite of the fact that the weigh is (I guess) one third or so, compared to my old lady.
    Those extrapolated demand curve graphs are only rough estimates more applicable to D speeders and tbo you really need to see the actual readings from the “electronic malarkey “ on a P speeder to see there’s no curve to be seen .

    9 + knots is just over pushing a bow wave for a 13 + M WL .
    That’s deliberate to get some load at D speeds the fuel burn is 18/20 L per side so 36/40 in all .EGT s are down @360 degrees .
    Dropping to tick over 600 rpm achieves 7,6 knots and from memory 15 L per side and mid forty % load .EGT s under 200 degrees .
    The props are big pitched and the hull SA is relative great due to the deeper than Ave V .

    When it lifts up for a given load the speed dramatically increases because the wetted area is suddenly reducing ( SA ) .

    So 65 % load is 14 knots , yet add another 15 , go to 80 % and we more than double the speed to 29/30 knots .EGT s 560/570 degrees the optimal for agglomeration management. That what I use to set P cruise the load value along with EGT,s - a combo of both .
    Add another 10 load to 90 % we only gain 3/4 knots .
    The next and final 10 % to 100 % ( depending on weight + fouling etc ) we only add another 2 knots if that !

    That’s definitely not a curve by any stretch of the imagination.

    So rarther than a curve with a planing hull any graph of load Vs speed , a planning boat should be S shaped .Theres a huge ( relative ) vertical gain in speed of 2x when its drag is lost for a disproportionately small amount of “load “ Actually 15 % .
    From 14 to 29/30 knots .

    Interesting your point ( blind of actual load “electronic malarkey “) fuel burn is linear more or less or a slight curve like a prop demand , with boat speed .

    So my point is the load graph vs speed does not follow a curve anywhere near resemblance of the fuel burn vs speed in a planning boat .

    And you generally have extrapolated one mirrors t, other that why our numbers differ .You have to guess , I actually just read .




    With a D speeder only , then a those curves you mention have more merit .I can see that ,but as explained virtually useless in a P speeder , because of the sudden change of drag when it planes .

    My boat weight fwiw is 17 tons dry so nearer 20 with cruising stores 2000 L fuel + 500 L water .
    But those stats comparison of my P boat with your old D boat are useless because as I said “ apples and oranges “
    Last edited by Portofino; 17-08-19 at 17:05.

  6. #6
    Join Date
    Jan 2009
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    Stratford on Avon
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    11,180

    Default Re: Cat 3126ta engine oil

    I have Cat 3126 DTi’s in my Azi. I used Exol Marine 123 SAE 30. It is about £60 for 25 litres from my local oil supplier. I understand that Cat branded SAE 30 is Exol 30. The marine version is allegedly better quality. For the price difference it is a no brainier.

  7. #7
    Join Date
    Oct 2007
    Location
    MK
    Posts
    1,810

    Default Re: Cat 3126ta engine oil

    Interesting thanks chaps - We use to pop the engine brather hose from RS2000 engines into a catch bottle to prevent it contaminating the air enter the Twin Webber 45DCOE carbs use to get an oily water probably moisture from air mixed with crankcase oil mist.

    If piped to the air on side of the turbo, I can see it would contaminate it, not sure if it would make a lot of difference to power, could argue an oily mist might even be beneficial entering/lubricating the turbo, albeit the cleaner the blades the better. There is a slight suction at the inlet, which might clear (suck) the gasses out, when into a catch pot, it would be at atmospheric pressure.... Mmmm not sure.

    Be interested if anyone knows if this has been done to other 3126s
    PRINCESS 45

  8. #8
    Join Date
    Dec 2009
    Location
    New Zealand
    Posts
    86

    Default Re: Cat 3126ta engine oil

    Quote Originally Posted by John100156 View Post
    Hi

    I am about to buy a boat with Cat 3126's, I am aware of the issues and have been in touch with Cat whom informed me the 6MK... models were later and did not suffer from some of the issues of the earlier engines.

    I could do with some advice on oil selection. As many of you know, CAT/Finnings recommend their monograde oil 30W. I will of course use 30W but wondered what others are using in their Cats?

    Someone from this parish has already recommended Exol Taurus 30, which to me seems perfectly fit for purpose, but are there other good quality oils I might use that others have used successfully. The 3116 and 3126 both use this Spec oil. Any advice/guidance welcome.
    My previous boat (c2003 Princess P45) had a pair of CAT 3126TA 420hp engines (6MK). My advice is to go with the CAT SAE oil (and coolant for that matter). It's expensive but not a huge cost in the grand scheme of things.

    James.

  9. #9
    Join Date
    Jun 2010
    Posts
    960

    Default Re: Cat 3126ta engine oil

    John, its very simple, oil is oil and the only thing which matters is specification and not old wives tales or other misleading information and hypothesis.

    Find the exact specifications of the CAT oil and search for the same or better specified oil and ensure you take on board any cleaning agents in the oil; CAT do not make oil, they only make marketing claims and by searching around you will find which companies make their oil and get the same or better specification oil for much less.

    If you are in the UK then Opie Oils are worth a look.
    I am old and wise because i was young and stupid.

  10. #10
    Join Date
    Jan 2009
    Location
    Stratford on Avon
    Posts
    11,180

    Default Re: Cat 3126ta engine oil

    Quote Originally Posted by Assassin View Post
    John, its very simple, oil is oil and the only thing which matters is specification and not old wives tales or other misleading information and hypothesis.

    Find the exact specifications of the CAT oil and search for the same or better specified oil and ensure you take on board any cleaning agents in the oil; CAT do not make oil, they only make marketing claims and by searching around you will find which companies make their oil and get the same or better specification oil for much less.

    If you are in the UK then Opie Oils are worth a look.
    The Cat branded oil is Exol.

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