T6 5-40. MPG

[Infotroll]

So I went from ford 5-30 to rotella 5-40 and lost 3-5 mpg . I have about 4000 miles on the T6 same driving conditions . So the argument I have heard is that is better for the engine but at the cost of mpg . After doing some math its more expensive to use the 5-40 even at 50% cost of the 5-30 so I will be going back to ford 5-30 . Anyone out here have any thoughts

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[nrmedic]

I had debated doing something similar, but with QSFS 5w40 Euro which is almost a 5w30. Guess I won't now.

 

[Gros Ventre]

Bearings are designed for the specific weight of lubricant. In my Navy service I have seen components with bearings designed for water lubrication. When you up the weight of oil you up the internal drag on the engine. Is it better for the engine? I don't think so. The single thing you can do to improve the engine performance is better filtration. Get a main filter with the lowest micron rating you can find and stick with it. Consider adding a bypass filter.

 

[TruckBubba]

Way back in the day when I drove worn out old air cooled VW's I used Castrol straight 40W which helped control oil usage, smoking, etc. Now I do follow Fords recommended viscosity and change intervals. They do design engines to work with a specific oil and the only change, IMO, that truck owners should make in that regard is interval change and the use of full synthetic oil.
Plus, I wouldn't put it past Ford to deny a warranty claim if they could prove use of incorrect type motor oil.

 

[Buyer2021]

Plus, I wouldn't put it past Ford to deny a warranty claim if they could prove use of incorrect type motor oil.

As they should in the case of an oil-related claim, IMO.

IMO folks need to remember that in modern engines like the current F150 5.0 the oil is critical to a lot more than just bearing lubrication - it also is the actuating fluid / metering force for injectors, VCT, hydraulic lash adjusters, etc.

It's almost assured that all of these systems (their many passages, orifices, bypass / pressure relief mechanisms, etc) are engineered for and to some degree sensitive to the specified oil viscosity characteristics; it shouldn't be surprising that deviating from that viscosity spec may have unanticipated and potentially detrimental consequences.

 

[Calson]

So I went from ford 5-30 to rotella 5-40 and lost 3-5 mpg . I have about 4000 miles on the T6 same driving conditions . So the argument I have heard is that is better for the engine but at the cost of mpg . After doing some math its more expensive to use the 5-40 even at 50% cost of the 5-30 so I will be going back to ford 5-30 . Anyone out here have any thoughts

There is something wrong with your presumption that changing the motor oil resulted in a 15% decrease in fuel economy. Something else changed or you did not fill the tank and drive a hundred miles and then refill the tank to check actual fuel burned.

 

[Roush Auto Detailing]

I use 5W-40 and have been since the first oil change and I did not see that large of a drop in fuel economy. Maybe 2 mpgs. Ford has a spec for use on 5W-40 oil. They say to use it when you are towing or hauling consistently and when you don't get below 0 degrees F; which I pull my detail trailer multiple times a week and our camper multiple times a year and don't get below 0 often in Western NC.

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