Oh no not another oil thread...Merc 25/40 Vis Delo 40

[Lou C]

I ran a couple of oil analyses over the past few years comparing the Delo straight weight I used for years and the Merc 25/40 that is specifically blended for inboard marine use. The Delo 40 was done during the 2011season and the Merc was done at the end of this season. Both held up well, the Delo was a high 30 weight (may have been due to some fuel dilution since fixed). The Merc oil performed even better staying in grade at a high 40 weight. Only major difference was that the Delo had a lot more zinc (1400 vs about 950). However a current sample of Delo may show lower zinc from what I have read. It would be interesting to see other analyses like Delo 15/40 vs the Merc and Mobil 1 in various grades.
It seems that the Merc stuff while expensive lives to to their claims.

 

[thumpar]

I have been using diesel oil. It doesn't have to meet the same EPA standards so usually has better cleaning properties. Where is the popcorn?

 

[Lou C]

I'd like to see if the 15w/40 from Delo and Rotella holds its viscosity as well as the Merc oil. If they do then the are a good less expensive alternative even tho Merc has never recommended that grade.
I recall reading that an engine oil cooler is what makes it possible to run the lower viscosity oils and that's why certain marinizers specify that oil and other lower viscosity grades. I guess most Merc engines don't have engine oil coolers.

 

[littlerayray]

My mechanic told me to use the specially formulated 20w40 ect mercruiser oil because a guy had same motor as me and tried a different oil same viscosity and his motor started knocking had to change oil o prevent further damage

 

[JoLin]

I use the Merc 25-40 (non-synthetic) oil because

1. Mercruiser recommends it.
2. It's available at WalMart.
3. The price difference for my once-a-year oil change is less than $10.00 per engine. That isn't even a blip on the 'cost of ownership' scale.

My .02

 

[HT32BSX115]

I use the oil in my "Sig" below and I've never had a problem!!

 

[Lou C]

Ah yes Rick but we tech nerds like to see numbers... Viscosity and TBN after a seasons use....

 

[thumpar]

My mechanic told me to use the specially formulated 20w40 ect mercruiser oil because a guy had same motor as me and tried a different oil same viscosity and his motor started knocking had to change oil o prevent further damage

I call BS on that. I have put almost every kind of oil in my Mercs, from cheap stuff to expensive to the diesel. The oil is not causing the knock.

 

[Lou C]

Only if what he was referring to was lifters tapping at a slow hot idle after running on plane for a while with a lower Vis oil like 5w/30. Some people have gotten low hot idle readings under those conditions.
Next season I'm going to get a few more data points like taking a temp reading of the oil filter after running on plane for a while. Just warming up on the water hose it gets to about 150*f....no engine oil cooler....

 

[HT32BSX115]

Ah yes Rick but we tech nerds like to see numbers... Viscosity and TBN after a seasons use....

That may be true.......What I use is highly classified.....if I told anyone, I would have to silence them!!

My mechanic told me to use the specially formulated 20w40 ect mercruiser oil because a guy had same motor as me and tried a different oil same viscosity and his motor started knocking had to change oil o prevent further damage

Yeah......and I'll bet that mechanic sells it too............

 

[Lou C]

We ought to have a section for oil analyses after running X oil for X hrs and then people would have real data instead of just our ramblings lol...like on Bob is the Oilguy...
Next I'm sending in a sample of the Merc High Performace gear lube that I pulled out of my Cobra when I winterized it the other day. Oil looked like it just came out of the bottle...

 

[JimS123]

I use the Merc 25-40 (non-synthetic) oil because

1. Mercruiser recommends it.
2. It's available at WalMart.
3. The price difference for my once-a-year oil change is less than $10.00 per engine. That isn't even a blip on the 'cost of ownership' scale.

My .02

Yeah, we spend 30 grand on a boat and then try to save a dollar and 78 cents on cheep oil.

But it seems like "everybody" does that.

If I ever suggest buying a used boat, please shoot me.

 

[Scott Danforth]

Ooh.....popcorn

 

[JoLin]

Yeah, we spend 30 grand on a boat and then try to save a dollar and 78 cents on cheep oil.

But it seems like "everybody" does that.

If I ever suggest buying a used boat, please shoot me.

Or, you can buy mine

Seriously, with few exceptions, I'm big on OEM. Generally means a longer service life and zero fitment issues. And if you shop around, not that much more expensive. Far as the oil is concerned, I really don't consider myself qualified to second guess the people who build the things. I don't think anybody else here is qualified, either.

 

[Lou C]

That's why I suggest people try doing oil analyses it's the only way to know if the oil stays in its viscosity grade well enough to protect the engine.
To me it really comes down to the Merc oil vs the 15w/40 that are rated for both gas and diesel. It seems that the Merc oil may be a better choice if you don't have an engine oil cooler.
And I bet that Merc's own recommendations come from the same source... Their own oil analyses. I recall reading that certain marinizers allowed the use of lower Vis oils but they equipped their engines with engine oil coolers. To me that is a critical difference. Most standard Merc and Volvo engines do not have engine oil coolers. While marine coolant temps are relatively low the oil temls can be high.

 

[HT32BSX115]

There's a few good reasons why one might want to oil analysis.

1. Diesels: determining the level of soot in suspension so you can change the oil just before the soot levels become too high and the oil is saturated.

2. All engines, determining the level of contamination to get maximum life out of the oil

3. Test for certain wear metals that can tell you how good your rod, main and cam bearings etc are doing.

With the exception of determining wear metal levels and maybe fuel or coolant levels in the oil, few with recreational marine engines run the oil anywhere near long enough for oil analysis to be of much benefit. (changing it every year or every 100 hrs doesn't even come close)

Oil Analysis could reveal some health info with an engine that you were going to buy used but you would want tests that came from several oil changes (not just one)

Since there's a LOT of experience (here and elsewhere) with people successfully using literally every kind of oil (automotive, marine, 10-30 to 15-50 and all the single grades etc) for thousands of hours,

I'm not sure that any analysis would be very conclusive......

 

[Lou C]

While many people have used all different oil grades there is no real proof that by the end of the season the oil had not lost viscosity. The wear this could cause will be very gradual over time but it will happen. While everyone says ".....and I never had a problem" the reality is that until it gets extreme you will not notice the wear but then it's too late. There is a reason why Merc OMC and Volvo recommended straight weights vs multi Vis oils. Even with only 20-30 hrs on my engine the straight 40 Delo sheared to a high 30. If I used 30 and the same thing happened it might have been in the high 20 range. The Merc 25/40 was still a 40.
I think that if we really had a number of conventional 10w/30-40 analyses I bet a fair number would shear down one grade. Just saying Id like to see some relatively scientific results.
Merc and OMC were recommending straight weights even before Merc started selling the 25/40 stuff they recommend now. This suggests to me that they tested conventional multi vis oils and found them less than adequate.

 

[HT32BSX115]

There is a reason why Merc OMC and Volvo recommended straight weights vs multi Vis oils. Even with only 20-30 hrs on my engine the straight 40 Delo sheared to a high 30. If I used 30 and the same thing happened it might have been in the high 20 range. The Merc 25/40 was still a 40.
I think that if we really had a number of conventional 10w/30-40 analyses I bet a fair number would shear down one grade. Just saying Id like to see some relatively scientific results.

I think it's more because automotive engines benefit from a multi-grade since they operate in FAR larger temp-swing environments.

Start up a car or truck in a -25F cold soaked condition with a straight 30 or 40 (or even 25W40) and the oil will be like tar!

Even with a 20W straight wt, while you have might oil pressure at the gage, it's likely not flowing anywhere it's needed any time soon! (you'd be running the bearings essentially "dry" for a time )

I am not sure you can use the oil analysis visc numbers all that accurately with a marine engine though . It appears that the test (ASTM D5481 - 13) is performed at 150C which is might be pretty common in an engine with a continuous block temp of say 230F (110C) ............Like a truck pulling a load up a long hill..................

No marine engine ever has a block temp of 230F. (unless you interrupt raw water flow..........then alarms are blaring and it's an emergency!)

I would expect that the peak oil temps in any recreational marine stern-drive engine are considerably less than 150C (~300F) on a continuous basis.

So even if you did have an oil with a resultant visc in the high 20's @150C (according to the analysis) , the viscosity at the actual oil temp in the engine would likely be higher because the oil is cooler.

So you would still be 'ok' using a 5W-30 (or other multi) (certainly any synthetic 5W-30 etc) Probably like all the anecdotal "evidence" seems to suggest...........

 

[Lou C]

I am not sure you can use the oil analysis visc numbers all that accurately with a marine engine though . It appears that the test (ASTM D5481 - 13) is performed at 150C which is might be pretty common in an engine with a continuous block temp of say 230F (110C) ............Like a truck pulling a load up a long hill..................

No marine engine ever has a block temp of 230F. (unless you interrupt raw water flow..........then alarms are blaring and it's an emergency!)

I would expect that the peak oil temps in any recreational marine stern-drive engine are considerably less than 150C (~300F) on a continuous basis.

So even if you did have an oil with a resultant visc in the high 20's @150C (according to the analysis) , the viscosity at the actual oil temp in the engine would likely be higher because the oil is cooler.

So you would still be 'ok' using a 5W-30 (or other multi) (certainly any synthetic 5W-30 etc) Probably like all the anecdotal "evidence" seems to suggest...........

But Rick why then do some marine engines have engine oil coolers, when you hardly ever see them on vehicles? I did some checking around, and it seems that the only marinziers that recommend multi vis oils, have equipped their engines with oil coolers. Just for the heck of it, I took an IR temp gun reading of the oil filter while the engine was warming up on the water hose. It was 150 *F with the engine idling on a cool fall day. Next season I want to take a reading after running on plane I know taking a reading on the filter housing is not the same as an oil temp gauge, but if idle is 150 and then we see 250 or more after running on plane, it makes the case for a better oil. An what do we usually see after we come off plane? Our hot oil pressure which will be a good bit lower (like 20 psi) than our cool idle pressure (40-45 psi). So that tells me something. Now on my old '98 Jeep with the 4.0 six, 165,000 miles, there is not much difference between cold and hot oil pressure. Cold is about 40, hot, 30. Cruising rpms on that vehicle are about 1800 rpm. On the boat...3600 rpm, exactly double.....

 

[HT32BSX115]

I too have noticed that many or most of the small block engines don't have oil coolers and most (or all) of the big block engines do have oil coolers. Probably the same reasons most cars and light trucks don't have them but trucks with towing packages do have oil coolers. (and you can add after market oil coolers for towing)

But I would say that the trucks (and other tow vehicles) that do heavy towing produce higher oil temps during that towing than any marine engine just due to the higher coolant (and block) temps.

I think I'd also like to do an oil temp test too!

We might all learn something!