Motor Oil - Synthetic or Rotella?

[Sharecropper]

I am fast approaching a point in time when I will need to install new motor oil in my GEP P400 engine. I have read the arguments pro and con until my Walmart readers fogged up. So I thought I would start this thread to ask for expert opinions.

My P400 long block arrived from GEP in a crate with, surprisingly, the correct amount of oil in it. I drained this oil in order to remove the cast aluminum pan for bung installation and the oil that came out appeared to be synthetic. It was a yellow-green color and had a weird smell. Didn’t really look like oil at all. Kinda glad I drained it.

I have always been a big fan of Rotella, because a long-time mechanic who I trust will use nothing but Rotella T4 15-40 in his Diesel engines. So my question is, does synthetic have any advantages?

 

[Senderofan]

Sorry to say I'm no expert......Long Block? Is this a long block that has never been run? If so......it may have been filled with break-in oil. You might have to add a break-in additive to what ever oil you go with ( Something with higher zinc content ).

As far as Rotella......I've been using T6 in two vehicles and two tractors for years. Rotella is good stuff! Not sure I'd use the full synthetic unless you run in very cold temps.....so probably T4 or T5.

Best of luck.....I agree with you in regards to doing extensive searches.....to the point of double vision

 

[fuzzytoaster]

Synthetic is supposed to resist heat break down better, resist acidification from age (not really a thing any more), have less evaporative loss, etc..

Unless you plan to run that engine long, hard, and often I don't see the cost effectiveness of it. Tests have shown conventional oils today are much better than they once were and their additive packages are pretty on point. It would be easier to use regular Rotella in a white bottle and service it every 5,000 miles (or more) or every year due to moisture if it's just sitting than guessing at oil life of your synthetic if you're trying to get the most out of it. By no means am I discounting using synthetic but it's economies of scale and value of the engine. Does your friend use the T4 in his $200,000 semi's? I think a few bucks spent on oil there would make me rest better at night.

 

[cucvrus]

More expensive. I am old school. I change oil every 2 K on my CUCV's. Or less on my OFF ROAD CUCV. I have changed the oil after 20 miles of hard OFF ROAD driving. My new truck gets serviced at the GM garage just like my M1009 did. they always use DEXOS oil. https://www.gmdexos.com/

Not that it matters but my new truck is easier to service because it has the oil life alert and I just get it changed as the percentage gets in the 20% or lower. That standard vs synthetic is an argument that could last till the next millennium. The choice is yours. Either way I don't see it getting used extra hard and not serviced as required.

 

[cucvrus]

May I also add I have used Fram filters on all my Honda lawn tractors and still have the same 4518 for 30+ years. One time a year I change the oil and filter. the Fram cost about $5. and the Honda cost about $20. It filters oil and it works and time has proven that. This year I came across 3 Honda filters at a yard sale for $1. all 3. I bought them. So I will use Rotella T 15 40 qt that is left over from changing the 7 qts in a CUCV and buying the 2 gallons to do so. Honda says 10w30. Still going. I think it will all work out. I currently have the Honda in the shop with the drain plug out. Looks like a little car engine. 2 cylinder water cooled.

 

[Karl kostman]

Sharecropper I run 3 855 series Cummins in military trucks another 855 in a semi for hauling been, a Unimog and an OshKosh snow plow and thats got a CAT engine in it. I have run Rotella 15 40 in everything for years now and have never had a single regret with it, except that I seem to be buying TO MUCH of it! Good luck and sometimes the new stuff just isnt any better than the conventional!
Karl

 

[Sharecropper]

Sharecropper I run 3 855 series Cummins in military trucks another 855 in a semi for hauling been, a Unimog and an OshKosh snow plow and thats got a CAT engine in it. I have run Rotella 15 40 in everything for years now and have never had a single regret with it, except that I seem to be buying TO MUCH of it! Good luck and sometimes the new stuff just isnt any better than the conventional!
Karl

Thanks Karl for your post. My feelings exactly.

And thanks everybody for your opinions. My new engine will not be turbo’ed and I can assure everyone that it will never break a sweat. Probably will never see mud and will only leave the pavement occasionally. So I will stick with Rotella T4 15-40.

 

[Sharecropper]

May I also add I have used Fram filters on all my Honda lawn tractors and still have the same 4518 for 30+ years. One time a year I change the oil and filter. the Fram cost about $5. and the Honda cost about $20. It filters oil and it works and time has proven that. This year I came across 3 Honda filters at a yard sale for $1. all 3. I bought them. So I will use Rotella T 15 40 qt that is left over from changing the 7 qts in a CUCV and buying the 2 gallons to do so. Honda says 10w30. Still going. I think it will all work out. I currently have the Honda in the shop with the drain plug out. Looks like a little car engine. 2 cylinder water cooled.

Rick - you may remember that I am installing a Spinner centrifugal oil cleaner on my engine, therefore I am not too concerned about the quality or effectiveness of the can filter. It is my understanding that the big differences between the brands pertains to the quality and longevity of the filtration media used inside the can. From what I have learned over the years, most of the main filter brands will remove particulate size down to 20 microns when new. To put this in perspective, a germ’s body is 1 micron wide. In a new engine, the clearances engineered between bearing surfaces average 5-10 microns. So even a new can filter will allow particulates and contaminates smaller than 20 microns to pass through and cause wear between bearing surfaces. The Spinner centrifugal filter, spinning at 6000 rpms with 35 psi oil pressure, will remove all contaminates down to 0.5 micron. That's HALF a micron, even smaller than a germ. I figured that I had invested so much cash in this new engine, I might as well spend a little more and keep the oil clean.

 

[Mainsail]

I have two vehicles that take 7 quarts for an oil change. Both the Hemi jeep and the 6.2 diesel get two quarts of synthetic and five regular.

Been doing that since the 90s when I read somewhere you get all the benefits of synthetic by using that approximate ratio.

 

[Sharecropper]

I read somewhere you get all the benefits of synthetic by using that approximate ratio.

Thanks for your post. Although I have already decided to use Rotella T4, I am curious - what exactly are the "benefits of synthetic"?

 

[Mainsail]

Thanks for your post. Although I have already decided to use Rotella T4, I am curious - what exactly are the "benefits of synthetic"?

A I remember it, you get less start-up wear. IOW, more protection in that period between the engine starting and the oil pressure building.
Less heat break-down
Other stuff

 

[Sharecropper]

A I remember it, you get less start-up wear. IOW, more protection in that period between the engine starting and the oil pressure building.
Less heat break-down
Other stuff

Yes that is probably true. However I am installing a 24-volt 2GPM aircraft pre-oiler pump on a momentary toggle switch to build oil pressure to all bearing surfaces during the glow-plug heating cycle. In addition, I am not turbo-ing the engine so heat break-down will not be a concern either. So I will stay with straight Rotella T4 15-40.

Thanks for your comments. If you haven't subscribed to my rebuild thread, I now invite you to. Just now getting to the juicy part. Link below.

 

[pmramsey]

non-turbo gets the regular 15-40 Rotella

Turbo gets the semi-synthetic 15-40 Rotella

My 1965 M54A1 with the turbo gets the semi-synthetic 15-40 Rotella. However, zinc additive for the flat-tappet portions of the engine is essential.

 

[Katavic918]

non-turbo gets the regular 15-40 Rotella

Turbo gets the semi-synthetic 15-40 Rotella

My 1965 M54A1 with the turbo gets the semi-synthetic 15-40 Rotella. However, zinc additive for the flat-tappet portions of the engine is essential.

Just curious and not trying to derail the thread. What zinc additive do you use and how much? I use 8 oz of zddplus into 5.5 gal of Rotella 15w40 conventional in my M35A2. May look at the semi synthetic next time.

 

[dependable]

One reason to run regular 15-40 in these is they are older generation diesels and the best way to keep their innards clean is to change oil. The synthetics last a lot longer, but they still load up with combustion contaminants, so to keep motor clean, oil changes have to be more frequent than duty cycle of synthetic oil.

 

[Katavic918]

One reason to run regular 15-40 in these is they are older generation diesels and the best way to keep their innards clean is to change oil. The synthetics last a lot longer, but they still load up with combustion contaminants, so to keep motor clean, oil changes have to be more frequent than duty cycle of synthetic oil.

I agree with this. Synthetic or not, you still need frequent changes.

 

[Abbylind]

In the aircraft engine world if you switch from mineral oil to synthetic you must replace all engine seals...reason? different expansion rates on the seals when using synthetic...

 

[Mainsail]

Yes that is probably true. However I am installing a 24-volt 2GPM aircraft pre-oiler pump on a momentary toggle switch to build oil pressure to all bearing surfaces during the glow-plug heating cycle. In addition, I am not turbo-ing the engine so heat break-down will not be a concern either. So I will stay with straight Rotella T4 15-40.

Thanks for your comments. If you haven't subscribed to my rebuild thread, I now invite you to. Just now getting to the juicy part. Link below.

I bought a turbo pre-luber back in the 80s for a turbo mustang II project that never got off the ground. Still have it! Right now it's being used as a pump for used motor oil, but I've thought about installing it in the CUCV.