Diesel oil viscosity?

donbrown

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Was running 15w-40 on 1990's 7.3 Ford and 2006 6.6 litre diesels. Went to 5w-40 synthetic. Someone at a truck stock said to look at 5w30 diesel oil? What do you guys think?
 

summ8rmk

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In the winter, the 7.3l starts much better with full synthetic 5w-40 than the 15w-40.
I only ran the 10w-30 one time, i just felt like the 5w-40 was a better choice. Both started well in the cold.

Duramax is fine with the old dino oil.
Personally, i like the synthetic blends.
U get the benefit of both oils.

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Reg2view

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5w-40 syn all day long in the D-max. Smallish oil cooler in the LB7-LLY-LBZ-LMM-LML. 15w-40 for towing in the summer. L5P has a better cooler, and needs it with the higher output. Can't speak to the 7.3.
 

boondocker97

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A 2006 Dmax doesn't have emissions so why would anyone recommend synthetic over dino?



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What does emissions equipment have to do with running synthetic vs conventional oil?

I think my 2017 6.7 Ford lists 10-30, 15-40, and 5-40 as acceptable depending on temperature and load factors. My operating range is -35 in the winter to 100 degrees in the summer while towing. 5-40 meets the range of use I could see so I run it year round for simplicity. If your owners manual doesn't list a 30 weight oil for what you plan to use the truck for then I wouldn't. It might let the motor spin a little more freely at cold or moderate temps, but it won't give the same wear protection at higher temperatures under heavy loads. There's reasons oil weights are specified for certain engines based on flow/pressure and load requirements.

The 7.3 was probably designed around using 15-40 since it was "the" diesel oil of the time. Pump, oil passages, and clearances were probably designed accordingly. As bad as they rattle in the cold I could definitely see running 5-40 in the winter though.
 

summ8rmk

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What does emissions equipment have to do with running synthetic vs conventional oil?

DPF will get plugged from the Ash from the older dino oils, so i am told.
As long as the dino oil meet cj4 standards it should be a low ash oil end be ok with DPF.

Also, there is a bit more diesel in the engine oil due to the regen process and synthetic oils can tolerate a higher percentage of diesel.


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summ8rmk

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WTF is Dino oil? and how would ash from the oil plug up a DPF?
Ha..... dino oil, from the dinosaurs... not synthetic.

From what i have read.
Supposedly, oil that makes it past the rings burns up in the cylinder and sends micro ash particles out the exhaust that eventually plugs up the DPF.
Ashless oil doesn't cause that issue.




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Blu Du

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i cant imagine the tiny bit of ash for the minute amount of oil would amount to anything compared to the diesel being burnt
 

Reg2view

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Also, there is a bit more diesel in the engine oil due to the regen process and synthetic oils can tolerate a higher percentage of diesel.


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Powerstroke and Cummins SCT - yes. D-max - no. D-max does not overfuel the motor to clean the DPF - uses a 9th injector in the exhaust downstream of the turbo at regen.
 

Reg2view

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A 2006 Dmax doesn't have emissions so why would anyone recommend synthetic over dino?
Firstly, startup below 10F. Big difference as temp drops. Yep, you can plug them in when it's really cold, but not always viable. Secondly, no guessing on oil life without sampling. Not many without fleets sample.
 

revrider07

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How many people garage there truck it starts good in there. Before i leave on a trip i let mine sit outside a couple days then start it just to make sure everything starts good. 5-40 in the winter for me.
 

boondocker97

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How many people garage there truck it starts good in there. Before i leave on a trip i let mine sit outside a couple days then start it just to make sure everything starts good. 5-40 in the winter for me.
That's not a half bad plan. Mine is garaged a lot, but most of the time it sits out for a few days while I'm doing sled prep for the weekend.
 
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