If oil thickness does not affect MPG, why CAFE?

[D.P.R.]

In another post I mentioned oil thickness affecting the MPG on my wife's Venza Hybrid. Some commenters, as you can imagine, agreed while others disagree. Honestly, I'm ambivalent. I want to dismiss it but it is hard because I am seeing it.
This got me thinking...why then manufacturers push for ever thinner oils to improve CAFE numbers if oil thickness does not affect MPGs?

 

[GW.]

In another post I mentioned oil thickness affecting the MPG on my wife's Venza Hybrid. Some commenters, as you can imagine, agreed while others disagree. Honestly, I'm ambivalent. I want to dismiss it but it is hard because I am seeing it.
This got me thinking...why then manufacturers push for ever thinner oils to improve CAFE numbers if oil thickness does not affect MPGs?

Small percentage points for each vehicle in the whole manufacturer lineup add up. They can also offset SUV’s and Trucks.

 

[JavierH19]

It depends. In the EPA testing it's done with a cold engine and the FE difference from cold makes a little difference but once warmed up the difference no longer exists outside of the lab.

 

[brillo54]

It matters much more in the theoretical world than the real world.

 

[SC Maintenance]

The stats I have read on the EPA tests show at most 3%. For an OEM 3% is HUGE!

However even assuming you get 3% in the real world which is likely not the case, your talking maybe 10 gallons a year. Of course that isn't nothing, but its not earth shattering either.

 

[kschachn]

In another post I mentioned oil thickness affecting the MPG on my wife's Venza Hybrid. Some commenters, as you can imagine, agreed while others disagree. Honestly, I'm ambivalent. I want to dismiss it but it is hard because I am seeing it.
This got me thinking...why then manufacturers push for ever thinner oils to improve CAFE numbers if oil thickness does not affect MPGs?

It does affect it. Controlled laboratory tests show about 1% to a max of about 2% per grade. Grades aren’t a singular viscosity, and it’s really the HT/HS so that’s why it’s not exact.

But as has been explained multiple times and in various ways, there are other and more significant variables in your driving that affect what you see, and therefore push the change due to the oil into the noise. In order to measure the singular effect from the oil takes a sophisticated laboratory test that isolates the relatively small change from the oil.

Many variables affect an observed fuel economy. Oil is one of them. However it’s in the noise and you cannot tease it out from what is a chaotic environment such as everyday driving. The energy content of the gasoline, even at the same station and irrespective of seasonal changes, is a larger variable than the oil. You’re lost before you even start.

 

[DCDG]

10 gallons per year to one driver isn't huge but to an automaker making millions of cars that's HUGE for CAFE

 

[kschachn]

Small percentage points for each vehicle in the whole manufacturer lineup add up. They can also offset SUV’s and Trucks.

Yes. It’s there or there would be no reason for manufacturers to spend boatloads of money on the pursuit.

 

[RDMgr]

It does affect it. Controlled laboratory tests how about 1% to a max of about 2% per grade. Grades aren’t a singular viscosity, and it’s really the GT/HS so that’s why it’s not exact.

But as has been explained multiple times and in various ways, there are other and more significant variables in your driving that affect what you see, and therefore push the change due to the oil into the noise. In order to measure the singular effect from the oil takes a sophisticated laboratory test that isolates the relatively small change from the oil.

Many variables affect an observed fuel economy. Oil is one of them. However it’s in the noise and you cannot tease it out from what is a chaotic environment such as everyday driving. The energy content of the gasoline, even at the same station and irrespective of seasonal changes, is a larger variable than the oil. You’re lost before you even start.

I also read that a 2.6 HTHS oil vs. a 3.5 HTHS oil, under the same operating conditions and parameters, will give a 1-2% energy benefit. This went further to say this could translate to up to 0.5 gallons over the course of 1000 miles.

 

[randomhero439]

The effect is magnified for a small truck fleet operating 10 long-haul trucks, totaling 1 million miles per year. A 3% improvement in fuel economy could save 3,100 gallons of fuel! The numbers get pretty wild when you consider there are 3M long-haul trucks on the road in the US. A 3% improvement is worth literally a billion gallons of diesel... just in that narrow usage case. 10 million tons of CO2 saved per year. All due to the pursuit of fuel efficiency.

 

[hemitom]

The stats I have read on the EPA tests show at most 3%. For an OEM 3% is HUGE!

However even assuming you get 3% in the real world which is likely not the case, your talking maybe 10 gallons a year. Of course that isn't nothing, but its not earth shattering either.

it is when it's millions or more !

 

[Zee09]

I see no difference in the last several new cars using 5w-30 over 0w-20
Three were Hybrids. Zero Mpg hit
Of course others may but I'm pretty anal about mpgs.. unfortunately.

Driving aggressively like most of the clowns i see daily effects mpg more by a long shot but they could care less. In a hurry to go nowhere and if a few people get killed by them oh well.

 

[gfh77665]

Simply airing up your tires saves more gas nationwide than CAFE thin oils ever could.

 

[4wd]

Simply airing up your tires saves more gas nationwide than CAFE thin oils ever could.

Heard the same at a bathhouse …

 

[Hall]

improve CAFE numbers if oil thickness does not affect MPGs?

It does (but on a scale individual car owners will never see).

The stats I have read on the EPA tests show at most 3%. For an OEM 3% is HUGE!

I don't know the %, nor does it matter, but it's extrapolated across every single vehicle the automaker builds, so it does add up, and yes, it's huge.