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View Full Version : Mobil 1 5w-40 Diesel Synthetic Vs Rotella 15w-40


Matt L.
07-20-2010, 11:09 AM
Saw this Mobil 1 diesel rated synthetic and thought it might be a good alternative.

What think you?

Thanks,

Matt

east tx skier
07-20-2010, 11:13 AM
No oil expert, but my understanding is that synthetic is fine as long as you don't plan to extend your oil change intervals as a result of using it. As far as its being "Diesel rated," I don't know what that means without more info.

TLR67
07-20-2010, 11:46 AM
I have changed mine twice a season for 20 Years with Standard Valvoline and Castrol Oil... No issues.. Not even a Valve Job yet.. Boat is pushing 1100 Hours.. Someone once told me dont over think it... Just keep the Oil Level Full and the filter fresh and go have fun... Its worked well over the years..

Also the same goes for Motorcycles as well... And pushing 16, 17,000 RPMs its been the same with my bikes as well..Keep them full and dont worry.. I think Synthetic Oils are simply overrated.. On bikes they can even cause clutch issues..

Craig
07-20-2010, 12:37 PM
I am also not an expert but it is my understanding that the purpose of using synthetic oil is to extend your oil change intervals.

I have heard a variety of arguments both in favor and against using it but have never really seen any compelling data that convinces me that it is a terrible idea.

ncsone
07-20-2010, 12:54 PM
Here is another thread from this forum from a while ago. It was posted by EngineNut, who works for Indmar. Note that it says not to use any oil that has a viscosity less than 15w.

See post #12 -
http://www.tmcowners.com/teamtalk/showthread.php?p=50200#post50200

vision
07-20-2010, 03:18 PM
I switched to the synthetic Rotella only because it has been shown, admittedly by Shell's internal research, to cause less wear in diesel engines than their std Rotella.

Changing the oil every 50 is easy and fast. Maybe 10 minutes of time. So my desire for using a different oil is to simply decrease engine wear, not extend oil changes.

The use of broader spectrum oils that flow easier at a cold temperature but maintain viscosity and lubrication at higher temperatures would intuitively provide better engine wear protection than oils with a narrower range of viscosity that did not flow well at low temperatures. The key, it seems, is whether a 5w40 oil truly has the same high temperature lubrication abilities of a 15w40. Certainly Shell's published test results would suggest that their synthetic 5w40 does have good cold and hot temperature performance, giving less engine wear over time.

But I am probably just being manipulated by good advertising...

UofU2727
07-20-2010, 04:30 PM
I run 10W40 Mobil 1 full synthetic, no problems at all. I just have had no problems with it and like it, "personal choice". It really doesn't matter if you use conventional vs. synthetic because most on here change the oil frequently or around 25 hours. Furthermore, I hear alot of talk about how you need to have 15W40 or 15W50 on here. Unless it voids the warrenty, it's not a big deal, 5W, 10W or 15W will work fine, it's mainly based on the fact that most marine engines run colder then typical automotive applications. Below will explain what oil ratings mean, you can read it off of the AMSOIL web site.


What does the SAE Viscosity rating on your Motoroil bottle mean?
How do they come up with this rating . . .really?
Most of the time when viscosity is explained words are used that are too technical for the average person to quickly grasp. This leaves them still wondering what the viscosity numbers really mean on a bottle of motor oil. Simply put, viscosity is the oil's resistance to flow or, for the layman, an oil's speed of flow as measured through a device known as a viscometer. The thicker (higher viscosity) of an oil, the slower it will flow. You will see oil viscosity measurement in lube articles stated in kinematic (kv) and absolute (cSt) terms. These are translated into the easier to understand SAE viscosity numbers you see on an oil bottle.

OK . . .What does a 5W-30 do that an SAE 30 won't?
When you see a W on a viscosity rating it means that this oil viscosity has been tested at a Colder temperature. The numbers without the W are all tested at 210 F or 100 C which is considered an approximation of engine operating temperature. In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210 (100 C). The difference is when the viscosity is tested at a much colder temperature. For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform at the cold temperature specified, but still has the SAE 30 viscosity at 210 F (100 C) which is engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.

trickskier
07-20-2010, 05:11 PM
No oil expert, but my understanding is that synthetic is fine as long as you don't plan to extend your oil change intervals as a result of using it. As far as its being "Diesel rated," I don't know what that means without more info.

Where is Bigmac when we need him??? :(

east tx skier
07-20-2010, 05:15 PM
I think the magic letters are ZDDP and he will come.

oldairboater
07-20-2010, 11:35 PM
I have been running synthetics in everything I own for years. Both boats, jeep, truck and two Harley Davidson's. The HD's are the reason I switched to synthetic in everything else. The switch from regular motor oil to synthetic lowered my HD's oil tank temperatures 20 degrees. I don't extended my oil change intervals in anything. 50 hours on the boats or twice a year. Every 3,000 miles in my jeep and truck. Every 2500 miles on the Harley's. Generators and mowers twice a year. Oil is cheap compared to engines and repairs.

vision
07-20-2010, 11:59 PM
The HD's are the reason I switched to synthetic in everything else. The switch from regular motor oil to synthetic lowered my HD's oil tank temperatures 20 degrees.

That seems like a good real world test! Good to hear as it makes me feel even better about my switch to synthetics.

Matt L.
07-21-2010, 03:32 AM
Rotella 15w-40 it is. Oil change this weekend. Put some serious hours on it at Lake Powell Last week.

Thanks,

Matt

oldairboater
07-21-2010, 11:27 AM
Both bikes had analog thermometers in the oil tanks and I seen the results with my own eyes in similar riding conditions immediately. 90's and 100's in the summer will cook an air cooled engine and it's oil. I ride those HD's a lot. Engines still tight and oil looks better between changes. The one downside to synthetics is that if you have a weeping gasket they will find it. Seen a good explanation about that on a video on time. People were complaining about synthetics causing leaks but the experts pointed out that the leaks were there already. The synthetics flowed better due to smaller molecules or layers of molecules and the leaks became more noticeable. I haven't noticed any leaks that concern me in anything I drive or own. They work for me and I like them ---that is my real test.That seems like a good real world test! Good to hear as it makes me feel even better about my switch to synthetics.

Bert
07-21-2010, 02:28 PM
Saw this Mobil 1 diesel rated synthetic and thought it might be a good alternative.

What think you?

Thanks,

Matt
Been using Mobil 1 15W-50 synthetic since new in my 91 pro star. Never an engine problem, it's clean and pulls strong. Heat is bad and synthetic is better for heat. Still change every 50 hrs. Some on here preach about it being a waste of money but... additional cost is cheap and it is your decision.
Use Valvoline 5W-40 in my cummins. 400,000 on it and same story.
I wouldn't use any thing but synthetic.

trickskier
07-28-2010, 09:15 PM
Where is Bigmac when we need him??? :(

I think the magic letters are ZDDP and he will come.

Only a few can appreciate those letters! :D;)