Oil recommendations - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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Old 12-07-2019, 01:09 PM Thread Starter
 
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Oil recommendations

Any advantages going to a synthetic oil? Reading about it says improved power better fuel mileage? Is it safe going from Rotella 15w40 conventional oil to synthetic??
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Old 12-07-2019, 05:40 PM
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Simply put.... For most folks Synthetic cost 2x much, lasts 2x as long.

End game is a push.

It boils down to how often you want to get under the truck....
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Old 12-08-2019, 08:34 AM
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I run synthetic Amsoil in mine, engine, trans, rear diff. As far as improved mileage, more power, etc... I've not seen or felt any. I've got a 99 Cummins that's been modded pretty much from day one. 165,000 on it and I decided to pull the cab to take care of some of the body cancer and pull the engine to fix a couple things and squeeze some more power out of it. It's got a fueling box, injectors, compound twins, fireringed head, etc... and was laying down 600hp for a long time. I wasnt easy on it either, it was my daily driver, towing truck and fun truck sled pulling. When I tore it down I found the block cracked, broken pistons, cracked head, etc.. only thing that was good was the crank and rods. I got new pistons and sent the entire rotating assembly out to have balanced. The shop said they couldnt believe the crank and rod journals were so nice yet, all they did was polish them and I can still use stock bearings. They asked what oil I've been using in it. That being said, synthetics are better as far as wear protection, long term, but if you're looking for mileage and power increases, save your money.
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Old 12-08-2019, 09:55 AM
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Quote:
Originally Posted by Lake Huron LML View Post
That being said, synthetics are better as far as wear protection.
Totally untrue. UOA's for Dino oil and Synthetic oil show the same wear metals in the same concentrations.

Its been proven over and over and over again......
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Old 12-08-2019, 10:22 AM
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All I run is Rotella 5w40 T6. I run it all year round. Great price and good protection. You will have no issues switching to it but one thing to note. If you have any slight oil leak issues on your engine or oil cooler switching to the T6 will likely cause more of a leak to appear. The synthetic molecules are smaller and more uniform. Great for heat transfer (especially for the turbo) but makes small leaks bigger. Dean
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Old 12-08-2019, 12:26 PM
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Quote:
Originally Posted by Dean E View Post
If you have any slight oil leak issues on your engine or oil cooler switching to the T6 will likely cause more of a leak to appear. The synthetic molecules are smaller
Is this a real post? "Smaller" ?? The Amsoil bypass deal filters down to 2 microns.

2 microns equals 0.002 mm. Two thousands of a millimeter.

Dino and synthetic oil flows through these just fine so a molecule of dino oil must be FAR smaller than 2 microns.

And you think that wont leak, but a synthetic oil will?
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Old 12-08-2019, 12:44 PM
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Quote:
Originally Posted by LMLLover View Post
Is this a real post? "Smaller" ?? The Amsoil bypass deal filters down to 2 microns.

2 microns equals 0.002 mm. Two thousands of a millimeter.

Dino and synthetic oil flows through these just fine so a molecule of dino oil must be FAR smaller than 2 microns.

And you think that wont leak, but a synthetic oil will?
What does a filter micron rating have to do with this? Do a bit of research. Synthetic oil will not cause leaks but it will cause small leaks to leak a bit more. Dean
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Last edited by Dean E; 12-08-2019 at 03:43 PM.
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Old 12-08-2019, 12:48 PM
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Quote:
Originally Posted by LMLLover View Post
Is this a real post? "Smaller" ?? The Amsoil bypass deal filters down to 2 microns.

2 microns equals 0.002 mm. Two thousands of a millimeter.

Dino and synthetic oil flows through these just fine so a molecule of dino oil must be FAR smaller than 2 microns.

And you think that wont leak, but a synthetic oil will?
https://www.cenex.com/about/cenex-in...gine-oil-myths

Read myth #3 and educate yourself. D
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Old 12-08-2019, 02:38 PM
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Quote:
Originally Posted by Dean E View Post
https://www.cenex.com/about/cenex-in...gine-oil-myths

Read myth #3 and educate yourself. D
A lot of that is due to the detergent packages in syn oils. Back in the day we used to put pepper in the coolant to stop small radiator pin hole leaks. The same thing is happening to your seals they become "sealed" with grime and crud and along come the high detergent synthetic oil and washes your seal clean.
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Old 12-08-2019, 04:08 PM
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Synthetic Oil

Quote:
Originally Posted by AlisoBob View Post
Simply put.... For most folks Synthetic cost 2x much, lasts 2x as long.

End game is a push.

It boils down to how often you want to get under the truck....
I buy Rotella T6 full synthetic oil for a few dollars more per gallon than T5 or T4 oil and I shop around and never pay more than $20 per gal and on sale $16 per gallon actually cheaper than many places out there just look around. I change any oil about 5000 miles and over the years have been sold on synthetics due to their better lubricating properties and most have more detergents and have kept my engines cleaner over the years. In the mid 90s I had an S10 with a 2.8 that I used Mobil 1 from the first oil change where at 323000 miles I had to replace the black RTV on the rear intake and the rockers were clean with no sludge. A valve started sticking around 460000 miles so I got rid of it.
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2003 Silverado Fass 165, 45% over injectors, Banks big head, Banks 6 gun, Banks Exhaust and filter. Bed Carpet, Pace Edwards electric Tonneau Cover. 122000 miles
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