Oil, Multi grade or single grade????

[RickyD]

Well I don't have a manual for my 1991 Caterpillar 3208s but I was perusing a friends similar and slightly older Cat book and noticed that multi grade 15-40wt was one of those in the recommendation chart. I was told that only 30 wt was approved for my old Cats. My Naiads use 15-40wt so it would be nice to only carry the one type. I certainly would not be afraid to add 15-40 to either engine if needed but an oil change is coming up and it would be a good time to change out if warranted. The Temp use range in the above mentioned chart would be extended for multi grade over the 30wt which is also fine. I know I'm splitting very thin hairs here but I'm curious what comments may come from this question.

 

[psneeld]

My 3208T Cats from circa 1987 ran pretty much trouble free for 5000 hrs and 3 owners who used 15-40wt.

They were the 320hp version... so I have to ask...who told you only 30wt was good for 3208s? I know the 3116s were on a single grade, but never heard the 3208s needed it.

 

[rslifkin]

Unless the manufacturer has a good reason to spec a straight weight oil or it's an application known to need it like a 2 stroke Detroit, use the multi-grade. Modern multi-grade oils are drastically better than they were 30+ years ago, so for the majority of applications, there's no downside to using them, only advantages.

 

[Comodave]

Our last boat had Lehmans that recommended 30 weight oil but the PO had been using 15-40 for 15 years and had no apparent problems. So I kept using the multi weight oil.

 

[Nomad Willy]

Unless the manufacturer has a good reason to spec a straight weight oil or it's an application known to need it like a 2 stroke Detroit, use the multi-grade. Modern multi-grade oils are drastically better than they were 30+ years ago, so for the majority of applications, there's no downside to using them, only advantages.

So are “modern” single wt. oils. The W15x40 wt. oil is only different regarding viscosity. So it stands to reason the multi-vis oils have a benefit when MV oil can be an advantage. Cold temperatures or hot temperatures signify a need for over 30w during the coldest temps the engine will see in normal service.

A truck (or car) that has oil spec numbers that are encountered on our trawler style recreational boats, are diesel powered and whereas the engine itself is exposed to the weather would need the low vis or high vis oil above and below 30w.

Trucks (and a few diesel cars) can use the MV characteristics to benefit. But re engines in heated spaces and isolated from cold cannot benefit from the MV oil. Most or all rec-trawlers have heated engine compartments and vented spaces to protect them from excessive high or low temps in or near the engine. We trawler skippers just don’t need MV lube oil.

Do we benefit from MV even if we don’t need it. It’s possible IMO. If you had a weak start batt the slight reduction in cranking drag could mean the difference between start or not in extreme temps. But what responsible skipper would be out in freezing temps w a weak start batt?

Then there’s the question of what harm is the viscosity improvers in the oil? I read somewhere that VI improvers were small rubber balls. They’ve prolly moved on from that. The oil must cost more of course. Im hopping someone else can pick up the ball re the downside of VI’s but I’m convinced we don’t need VI improvers. So why use them?
A lot (or some) emphasis is placed on how modern we are or appear to be and using/buying the latest products could be a cheap road to putting ourselves in the “to be admired and respected” category. That could be a powerful force.

Over my trawler years I used straight 30w RPM DELO oil and never had any apparent need for MV. I lived in Alaska over 90% of that time (about 10 yrs) and never had the engine hesitate to crank smartly. My Mitsubishi engine however was equipped w heaters/glow plugs. Not that it needed that but it was equiped w them. Just saying.

Sorry no proof read .. on the go.

 

[rslifkin]

Even when "cold" is 70* F there's still a significant difference in viscosity between a 30 or 40 straight weight and 15W40. The 15W40 will be thinner, leading to a bit faster cranking, but also better oil flow (especially to splash lubed components like cylinder walls) while the engine is warming up. For recreational boats that often have a lot of cold starts relative to running hours (unlike commercial boats) that cold start wear can make a difference.

I've been running 15W40 in the boat, but 5W40 in the dinghy outboard for easier starts (spec for it says any xW30 or xW40 is appropriate and I already have other stuff at home that uses 5W40). I've debated swapping the boat engines and generator to 5W40 for better cold start flow but haven't felt it worthwhile considering it's only a handful of times per year that the boat gets started with the engines below 50 - 55* F.

Modern viscosity improvers have come a long way both in terms of shear resistance and other improvements. Plus, base oils have improved and often have a higher viscosity index to start with, so for oils that don't have a huge viscosity spread (like 15W40) there isn't necessarily a huge amount of VII involved anyway. That's also why some of the wider spread grades (like 5W40) only come in synthetic, as the amount of VII needed to meet the spec with a conventional base oil would be excessive and lead to more viscosity loss due to shear while in use.

 

[RickyD]

My 3208T Cats from circa 1987 ran pretty much trouble free for 5000 hrs and 3 owners who used 15-40wt.

They were the 320hp version... so I have to ask...who told you only 30wt was good for 3208s? I know the 3116s were on a single grade, but never heard the 3208s needed it.

i THINK IT WAS THE GUYS WHO SURVEYED THE ENGINES ON PURCHASE. While we typically don't get any high heat here on the water the 15-40wt has a broader application chart. Now that I have seen it in a Cat manual, I'm switching.

 

[psneeld]

i THINK IT WAS THE GUYS WHO SURVEYED THE ENGINES ON PURCHASE. While we typically don't get any high heat here on the water the 15-40wt has a broader application chart. Now that I have seen it in a Cat manual, I'm switching.

Maybe I missed a small point...so are you switching to 15-40wt or to the straight 30wt?

 

[Southern Boater]

Well I don't have a manual for my 1991 Caterpillar 3208s but I was perusing a friends similar and slightly older Cat book and noticed that multi grade 15-40wt was one of those in the recommendation chart. I was told that only 30 wt was approved for my old Cats. My Naiads use 15-40wt so it would be nice to only carry the one type. I certainly would not be afraid to add 15-40 to either engine if needed but an oil change is coming up and it would be a good time to change out if warranted. The Temp use range in the above mentioned chart would be extended for multi grade over the 30wt which is also fine. I know I'm splitting very thin hairs here but I'm curious what comments may come from this question.

On boatdiesel.com, “dave” who is regarded as the oracle of Cat engines, has recommended the use of a mono 30 grade oil, stating he has customers that are seeing reduced smoke on start up and less oil consumption generally.
My boat has always used the Cat 15w/40 oil, and I found a clever source locally, a Cat specialist who has his own oil supply who could have easily persuaded me to buy his product, but strongly suggested not to use the mono 30 and stay with what has been previously used.

 

[Nomad Willy]

MV looks to be higher tech and better because of it.

Rslifkin wrote;
“ Modern viscosity improvers have come a long way both in terms of shear resistance and other improvements. Plus, base oils have improved and often have a higher viscosity index to start with, so for oils that don't have a huge viscosity spread (like 15W40) there isn't necessarily a huge amount of VII involved anyway. That's also why some of the wider spread grades (like 5W40) only come in synthetic, as the amount of VII needed to meet the spec with a conventional base oil would be excessive and lead to more viscosity loss due to shear while in use.”

Yes the 30w oil now is probably significantly better in many ways than the single wt. oil they used-to run 40 years ago.
And mentioning the fact that VI is bad enough to avoid by choosing oil that has a minimum spread in viscosity rating like 10w30 instead of 10w40 indicates it is to be avoided. Most people jump on the bandwagon of newer products assuming they are better. For our trawlers straight 30w is better. Many many commercial engines are run w 30w today because for the same reasons they used it 40 years ago.

 

[alormaria]

Unless there is a good reason to change, you should continue using what the engines are happily running.

 

[High Wire]

It’s amazing how the simple chart in every engine owners manual gets misinterpreted.
The key is the word AMBIENT ( the temperature immediately surrounding the engine). Determine what the lowest ambient temperature that your engine will be started. Even in Florida, in the morning, your engine room temperature may get below 70F if you didn’t run the day before. If ambient <70F then multi-viscosity is almost always recommended. Straight 30 for “cold” starts 70 and above. Straight 40 you better have some form of oil heater.

 

[RickyD]

Maybe I missed a small point...so are you switching to 15-40wt or to the straight 30wt?

I'm going to the 15-40 from the 30wt. That way I only have to stock one oil for my engines and stabilizers. Now I'm going to double check the oil requirements for my two generators. The 15-40 will probably be fine but I'll check. I don't use them much and I very rarely have to add oil. Last summer I did the whole oil/filter/impeller/air filter, change on both. I'm sure I used the Delo 400 30wt in them. Both are Yanmars. One is a two cylinder the other is a 4. Those I have books on so I'll check when back at the boat Saturday.

 

[RickyD]

Oh, regarding ambient temperatures, here in southern California we get some cold mornings in the 30's, not many, and we get some days that the engine room will be over 100, not many. Last two weeks of August, then Sept. and first week of October can be hot. Then the West wind pipes in, our air conditioner, and relief is at hand. Man I love the Fall. We boat all year round.

 

[RickyD]

I just looked at the Yanmar website and they are talking about 15-40wt. It's all good (I actually hate that phrase).

 

[tiltrider1]

For most of us in the lower 48 it really doesn't matter if its 30wt or 15-40wt. Its going to take some very Indepth and expensive research to truly answer this question. I think switching just to manage oil inventory is as good a reason as sticking to 30wt because you think it might reduce smoke.

Having the right amount of the wrong oil will get you further than not having enough of the right oil.

 

[Bacchus]

One factor I pay attention to when selecting oil for my boat diesel is the API Grade and I haven't noticed that even mentioned in the conversation so far... nor is dyno vs syn. I don't mean to start an anchor argument but both can be important when choosing lube oils for our application.
The best article I have found that addresses marine engine applications vs the typical truck / auto diesel application that has little resemblance to the needs of a marine diesel, is from Cox Engineering. I've posted a link on my Bacchus website in the Useful Links section... Cox Eng -Oils for Yacht Engines.
https://dkloeber.wixsite.com/bacchus/links

While API grades by definition are backward compatible, I subscribe to the practice of using the grade recommended by my eng mfg and put little faith in the "newer is better" philosophy. Cox discusses the need to moved up an API grade or two when some grades are obsolete but caution against some of the newest grades engineered for emission control needs that none of us have to contend with.
IMO it's worth a read even if you choose to make your decision different than their recommendations. I also agree with some of the sentiment that there may be very little practical difference in performance between the "ideal" choice for any engine/application and a "second or third place" choice. Based on the article though, there may be some choices to stay away from. Even those will not prove catastrophic (IMO) and I'm sure there are anecdotal instances where they do just fine.

 

[rslifkin]

MV looks to be higher tech and better because of it.

Rslifkin wrote;
“ Modern viscosity improvers have come a long way both in terms of shear resistance and other improvements. Plus, base oils have improved and often have a higher viscosity index to start with, so for oils that don't have a huge viscosity spread (like 15W40) there isn't necessarily a huge amount of VII involved anyway. That's also why some of the wider spread grades (like 5W40) only come in synthetic, as the amount of VII needed to meet the spec with a conventional base oil would be excessive and lead to more viscosity loss due to shear while in use.”

Yes the 30w oil now is probably significantly better in many ways than the single wt. oil they used-to run 40 years ago.
And mentioning the fact that VI is bad enough to avoid by choosing oil that has a minimum spread in viscosity rating like 10w30 instead of 10w40 indicates it is to be avoided. Most people jump on the bandwagon of newer products assuming they are better. For our trawlers straight 30w is better. Many many commercial engines are run w 30w today because for the same reasons they used it 40 years ago.

VII isn't necessarily bad, but there can be some issues that arise when too much of it is used, such as losing viscosity when the oil experiences too much shearing. More so in engines that are known for shearing oil (such as diesels with HEUI injection), not as much of an issue in other engines that are easier on their oil. Basically VII can do very useful stuff to oil, but it's not a magic bullet to make oil that stays the same viscosity at any temperature.

 

[Nomad Willy]

One more point I’d like to discuss is oil flow at start-up and residual oil that is always there at shut-down.

Two stroke or four strike oil comes to rest at shut-down. So an oil film is left for start-up. I’ve never seen any info that shows more oil is left on engine parts at shut-down w low vis oil or high vis oil. I’ve always believed higher vis oils leave more oil on contacting parts.
I did however, have a personal experience showing me that much more oil is left at shut-down w high vis oil.
I was running and flying an ultralight aircraft w a two stroke snow mobile engine. One day after a flight I pulled off the exhaust pipe off and looked into the exhaust port. It looked like someone had used a brush to apply oil to the piston skirts. I put my finger to it and saw/felt that it was oil. For some time I had been running Bell-Ray full synthetic oil of the highest viscosity available. i-pad batt dead. Later …..