Fuel usage to base oils change intervals

[BB marine]

I send my oil samples out after each oil change, engine oil and reverse gear. I Started after the 50hr break in oil change. I now have 324 hrs on the engine and 4 oil changes. Each oil change sent out for analysis. Except for first 50 hr no oil report because it was break-in. 2nd, 65 hrs (125 engine hrs) 3rd, 109hrs (134 engine Hrs) 4th, 92 hrs ( 326 engine HR). I now have a small amount of reports to set up a trend for my D3. For the most part all wear metals have been in range using a universal averages. All on the high side of the averages but with in range based on the comments provided by Blackstone Labs. My last oil analysis came back with a increase in wear metals, the two that increased the most were Iron and Copper. Iron was 40% more PPM and Copper was 30% PPM. When I read this report I was surprised. Last oil change (109 Hr) had 15 hr more hours of run time and the oil sample came back stating this was a good oil use interval.This oil analysis came back saying its time to change the oil. What changed ? I called and talked to the Lab and the question was asked did you change you running conditions on this oil interval? Yes I started running at a higher cruising RPM more often and for a longer period of time. That was my answer of why! Last year I decided to run the engine at a higher RPM (3360 approx.70% load) to increase our cruise speed to 13Kts. I keep a ship log which has all fuel consumed recorded. I looked at the difference in fuel usage from last oil change to this oil change. 109 hrs, 281.8 gallons of fuel used, average fuel usage was 2.57 GPH. Present oil change 92hr, 386.87 gallons used, average fuel usage was 4.2 GPH. Based on this I'm going to use 300 gallons of fuel as my base line for oil changes. If my average cruising fuel consumption is approx 2.5 gph I'm good for 120 hr oil changes. If my average is approx 4.2 gph I'm good for approx 71 hrs . I realize I'm over analyzing this ! I worked in reliability department for to many years :shock:. Many articles about diesel engines state Hrs of run time is irrelevant to the engines life expectancy because it doesn't take usage of hours into account. Gallons of fuel used is a more accurate way to determine life expectancy of a diesel power plant. Why not use this same theory for oil change intervals while cruising?

 

[knotflying]

I guess the question is, if you find a reading out of whack what are you going to do? On my plane it was easy to determine what part was wearing by the metal and you could remove each cylinder and work on it.

 

[BB marine]

I guess the question is, if you find a reading out of whack what are you going to do? On my plane it was easy to determine what part was wearing by the metal and you could remove each cylinder and work on it.

Wear metals are common in all oil analysis. The greater the number PPM of say iron the more abrasive the oil can be along with aluminum, copper, chromium, lead and tin. I don't use oil analysis to tell me I'm having a catastrophic failure. Its to late! I use it to tell me what the condition of my oil is and if I have destructive insolubles ,soot, antifreeze, water of higher then normal wear metals that are reducing the lubricating properties of the oil. Then determine why the levels increased. In my case it was higher rpm usage with this oil interval. The oil is to keep wear to a minimum. There is always going to be some wear and thus wear metals in the oil. The object is to maintain the oils lubricating properties to help maintain the longevity of the engine. filtering, and monitoring its condition helps with this. The higher numbers of iron and copper in the sampling were not indicating a problem with the engine. It was an indication that because of the number of revolutions the engine had made the wear metal particles were up and it was time to change the oil. Or maybe over do for an oil change. I do agree Mike that if you use oil sampling to tell you you have a major failure its to late! You have to rebuild it anyway.

 

[Salty7]

I am not familiar with your engine or which oil you are using but had a similar experience with Cummins B marine engines and Delo oil. I finally figured out that the engine was running the lube oil at about 260F which is too high for a conventional oil. I switched to synthetic Amsoil Heavy Duty Diesel Oil and all the metal and soot numbers dropped like a rock on the lab analysis. Turbocharged, aftercooled engines run the oil hot, the faster you run the hotter the oil. Synthetic oil shines in that area being able to tolerate much higher temperatures without thermal breakdown. There is also an added benefit - the oil additive package is able to contain contaminants very well too, less soot and wear metal along with a better additive package means you can stretch your oil change out for longer without detriment. The lab figures don't lie and switching to synthetic oil made a huge improvement in the lab numbers I was getting. The first thing I did when I purchased my tug was to switch to full synthetic oil in the Yanmar, the previous owner didn't think it was important but it really is.

 

[knotflying]

Yanmar specifically states to use Synthetic.

 

[knotflying]

BB Marine,

Good points on your last post. Definitely seeing traces of water or antifreeze in the analysis will be a good indicator that you have a problem that needs to be investigated before it gets worse.

 

[BB marine]

I am not familiar with your engine or which oil you are using but had a similar experience with Cummins B marine engines and Delo oil. I finally figured out that the engine was running the lube oil at about 260F which is too high for a conventional oil. I switched to synthetic Amsoil Heavy Duty Diesel Oil and all the metal and soot numbers dropped like a rock on the lab analysis. Turbocharged, aftercooled engines run the oil hot, the faster you run the hotter the oil. Synthetic oil shines in that area being able to tolerate much higher temperatures without thermal breakdown. There is also an added benefit - the oil additive package is able to contain contaminants very well too, less soot and wear metal along with a better additive package means you can stretch your oil change out for longer without detriment. The lab figures don't lie and switching to synthetic oil made a huge improvement in the lab numbers I was getting. The first thing I did when I purchased my tug was to switch to full synthetic oil in the Yanmar, the previous owner didn't think it was important but it really is.

I agree a synthetic is going to give you a longer interval and hold up to the higher temperatures. Yanmar recommends the synthetic, Volvo uses non synthetic. I use Rotella T4 15W40 which is known as a heavy duty oil for extreme conditions. My post wasn't to be an advocate of oil sampling or to debate which type of oil is better or worse. It was to give my thoughts on Engine hour Vs Fuel usage for oil changes. Volvo states oil changes to be performed 100-200 hr or at least every 12 months.What does 100-200 HRS mean ? My theory is its based on how you run the engine. 100 hrs running time at an average RPM of 2000 rpm is very different from 100 hrs of an engine that is run at 3600rpm. In my case 2017 109hrs average RPM 2200rpm, oil sample came back oil in good condition all wear metals look good may be able to extend oil change. 2018 92hrs increased cruising speed to 3360 rpm, oil sample came back good, but in comment section it stated "your wear metals increased while still at an expectable level the numbers are at the upper end of the limits. This is do to the max oil interval.It is time to change the oil. My question is what is the best was to gauge how many hours should I run before changing oil? My answer is Gallons of fuel used instead of hrs. For many this is of no concern because 60 or 70 hrs a season is all that many run their engines. If the boat is used and engine hours are 100 to 200 a season it is something to think about.

 

[Salty7]

Brian in my experience number of hours versus oil condition, based on lab testing, did not always correlate. My last boat was pretty much run at the same engine speed most of the time while cruising (90% load, 890F EGT), some years it sat more, some years it ran more. I owned it for 15 years and switched to full synthetic in about year four. My conclusion is absolutely that if you run Delo or Rotella versus a full synthetic for the same number of hours and the same engine speed the wear metals and soot was higher on the non-synthetic oil and much, much, lower on the full synthetic. I'm not debating who has the best oil I'm sharing real life experience using lab analysis over 15 years of operation. On over the road trucks, they do the lab analysis and often only change the oil filter, not the oil and keep on going when running full synthetic. I don't know any reason why you could not run full synthetic in your Volvo and get lower soot and wear metal numbers, what's not to like? You change the oil when the lab says so or pick a number of hours, you can choose what gives you comfort. I found I could easily go 250 hours and have virtually no wear metals and TBN numbers that were almost the same as when the oil first poured, being conservative I would then change the oil. This business of changing oil because it has been a year or 100 hours doesn't make much sense when the lab gives you answers but I was more comfortable knowing it was changed and fresh at 250 hours. The set calendar time or number of hours oil change harkens back to days when oils turned very acid with time, a modern full synthetic simply does not do that, dino oils still do and need to be changed much more often.