Engine oil weight

Don S/V ILLusion · Oct 18, 2013

I find it hard to imagine a reason why changing from one to the other would have any effect. They both have the same viscosity and characterisics when warm.

rufus1138 · Oct 18, 2013

i just bought my h33 and the engine was serviced shortly before my purchase, after researching the oil selections for diesels im going to use shell rotella t6 full synthetic, from my automotive and jet engine experience full synthetic multi-weight oils that are properly engineered are the best choice you can make.

heck the aircraft industry has been using synthetic oils for 30 years or more because they're the only thing that will hold together in a jet turbine doing a couple hundred thousand rpm.

Benny17441 · Oct 18, 2013

It looks like your engine may be running cool enough at normal operating temperature to allow the multigrade to do the job it was designed for. That is to have a floating weight value between 15 and 40 depending on engine temperature. It is easier on startup and improves burn rate.

Benny17441 · Oct 18, 2013

I'm noticing a number of folks switching to the synthetic oils. I agree they are superior lubricants and can last a lifetime when working in a clean enclosed piece of equipment like a transmission but in an engine where it is exposed to combustion byproducts and contamination it does not seem to provide an acceptable bang for the buck. On some of the older engines the gaskets do not seem to hold up as well to the new lubricants so we see a larger incidence of leaks. Today's regular blend oils are excellent and provide just as good protection as the synthetics; perhaps for a shorter interval but we seem to change our oils well before they degrade.

Ralph Johnstone · Oct 18, 2013

Hi Ken,

Going way out on a limb here, any chance the engine is running cool seeing as how viscosity SEEMS to be having such a large effect here ?

rufus1138 · Oct 18, 2013

Benny17441 said:
I'm noticing a number of folks switching to the synthetic oils. I agree they are superior lubricants and can last a lifetime when working in a clean enclosed piece of equipment like a transmission but in an engine where it is exposed to combustion byproducts and contamination it does not seem to provide an acceptable bang for the buck. On some of the older engines the gaskets do not seem to hold up as well to the new lubricants so we see a larger incidence of leaks. Today's regular blend oils are excellent and provide just as good protection as the synthetics; perhaps for a shorter interval but we seem to change our oils well before they degrade.

synthetic oils engineered for a specific purpose (motorcycle wet clutch, diesel, jet) can be optimized to suspend solid particulate material at an immensely superior level to natural oils. one of the most glaring benefits has been in the 4 stroke street motorcycle with a wet clutch where oil engineering has been the result of a huge boost in performance, i know my r6 saw an insane difference when i switched to a full synthetic racing oil that had the proper additives.

Eddie7045 · Oct 18, 2013

Rule # 1 : Don't go screwing around with oil additives

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Steve Dion · Oct 18, 2013

rufus1138 said:
i just bought my h33 and the engine was serviced shortly before my purchase, after researching the oil selections for diesels im going to use shell rotella t6 full synthetic, from my automotive and jet engine experience full synthetic multi-weight oils that are properly engineered are the best choice you can make.

heck the aircraft industry has been using synthetic oils for 30 years or more because they're the only thing that will hold together in a jet turbine doing a couple hundred thousand rpm.

Waste of money. These engine never see 4000 rpms let alone a couple hundred thousand. If it was superior they would be recommending it like most of the auto mfg.

A of regular Rotella can be had for $15.00.

Ralph Johnstone · Oct 20, 2013

Ken13559 said:
I've a temperature scanner so i can measure the mixer elbow and engine body but what temp number should i be looking for?

According to the manual (which I have illegally scanned here), the range is 160-185 F. I seem to run about 175 when cruising at 2700 RPM.

I think if you load the engine for about an hour and then shoot the top of the thermostat housing with your scanner, you should have a reasonable idea of what the temperature is.

petersea · Oct 20, 2013

Ken are you suggesting that the different brand and viscosity of oil is responsible for your loss of RPM's ?? Even changing the oil weight (from 10-40 to straight 40 ) should have no or extremely little effect on RPM's ) and the brand of oil should have no effect on rpm either. Like Don mentioned I don't see this being possible especial for a 400 rpm loss. I think you have other problems. My suggestion is change the fuel filter and check the exhaust elbow................let us know but really don't think it has anything to do with oil.

petersea · Oct 20, 2013

Ken13559 said:
I figure an SAE40 oil would be heavier than 15W40 ones. The multigrade means its viscosity don't change too much with higher temp and its light enough for cold weather. As my engine is 11years old, I thought a heavier oil would better seal any slack in piston rings. Forgetting that it probably is a little heavy on the engine too.

Ken........ I think you are maybe over thinking this. 11 years of normal boat usage (less then 50 hours a year) is nothing for these engines. So unless you are an extremely high time user and even then changing oil weight and stp type additives are unnecessary and have little value. Stick with the manufacturers recommended spec. These engines will go for thousands of hours with manufacture recommended maintance and recommended oils ! !

Ralph Johnstone · Oct 21, 2013

petersea said:
My suggestion is change the fuel filter and check the exhaust elbow.

Hey Ken,

Looking back at your original post and referring to what Petersea has mentioned (you can see how busy I am at this time of the year), I too would have to suggest that your changing of oil viscosities is probably coincidental with some other problem slowly appearing.

Rethinking this, my guess (and it's nothing more than a wild guess) would be the mixing elbow followed by the fuel filters. These little buggers (my elbows at least) are continuously plugging up and the one below (which I chopped up a few years ago) had a gas passage of about 1/4" diameter. Output at WOT (loaded) was still 3,500 RPM and I'm not underpropped nor excessively out to lunch. Don't ask me how it worked but it did. Mind you, it wouldn't be too many more running hours before the RPM would start to drop.

Do let us know how it turns out as this is one of the more interesting problems here.

Eddie7045 · Oct 22, 2013

Hmmm, somehow I'm not surprised. The oil additive

Ken13559 said:
Ralph, we can rule out mixing elbow as I recently had it decoked. As for the fuel filter ... I must admit I've never changed it for ..years .. since I didn't like bleeding air from fuel system as it gets pretty messy.
Alright, I'll bite the bullet :cry: and try changing fuel filters and see if that helps.

should have been my first clue. Have a nice day folks.

petersea · Oct 22, 2013

Ken13559 said:
Ralph, we can rule out mixing elbow as I recently had it decoked. As for the fuel filter ... I must admit I've never changed it for ..years .. since I didn't like bleeding air from fuel system as it gets pretty messy.
Alright, I'll bite the bullet :cry: and try changing fuel filters and see if that helps.

Ken, Don't forget you most likely have two filters, an in line (between tank and engine) and a engine mounted filter. (primary and secondary) Change them BOTH ! Try pre-charging the filter when changing them ( refill them with fresh fuel from a can rather then try to pump fuel thru them) and that should help reduce the mess. Most of the time I was lucky enough that I did not have to bleed an injector but just the fuel pump. All in all it is not a bad job and you should know how to do it just with some degree on competency in case of an emergency, plus will save you some money on mechanics bills !

Engine oil weight

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