Real Data: Oil Viscosity vs. MPG's

[Phishin]

I am running a 30 weight blend in my 2010 Accord. 1 part Mobil 1 0w40 to 2 parts Mobil 1 Advanced Fuel Economy 0w20.

Got back today from my honeymoon. Drove the Accord from Angola, IN to Orange Beach, AL.

Here is the mileage breakdown from our trip:

920 miles from my house to the condo. That's 1840 total miles, there and back.

I actually drove 2223 total miles. That's 1840 miles for the round trip, and 383 miles of traveling down there during the week.

I burned a total of 68.6 gallons of gas, which comes out to an overall average of 32.4 miles/gallon at a total expense of $223 for fuel.

Both getting there and coming home, I covered the 920 miles in 13.25 hours. Therefore, including fuel stops, I averaged 69 MPH. Yes, I was driving fairly fast. A couple of times, the 2.4L engine hit 6k RPM's when I mashed the pedal going over 90 MPH already.

I was suprised by my fuel economy. It appears my thicker than necessary oil isn't harming my fuel economy much.....

Just some data.....

 

[Kuato]

Got statistics for same trip with a different oil?

 

[coolbird101]

I have been experimenting some with 20 vs 30 weight oils and have reached the conclusion that any difference in mpg are undetectable by me and is lost in (noise) in my data. The differences have to be there, but it is so subtle I can not accurately measure it.
Thank you for sharing your findings.

 

[tig1]

I just got back from a 2900 mile trip to Florida this week. I got 32 MPG going and coming running at 72 MPH which is 2500 RPM in my I4 Fusion. No oil consumption since my last change, and I had 4K on the oil when we left for the trip.

One question: Why use an oil that's thicker than your engine calls for? I use only 0-20. Can't see a need for anything heavier. Just wondering.

 

[JHZR2]

I dont think it ever was intended to change MPGs much...

The reduction in viscous drag, if improving MPGs 3% on a 30 MPG car is less than 1 MPG. These incremental changes surely dont improve it even 3%.

But a half an MPG in a fleet, or across all motor vehicles in the USA is indeed millions of barrels of oil saved, which is why they do it.

 

[2James1]

My 2005 Malibu V6 is rated for 29 Hwy according to fuel economy.gov. I use Mobil 1 5w30 which is thick for a 5w30. And regularly get 32mpg+ hwy and the other day from Pittsburgh to Williamsport and back averaged 35.6mpg hand calculated. I am impressed by this drivetrain.

 

[Phishin]

Originally Posted By: Kuato
Got statistics for same trip with a different oil?


No. All I have is what others have reported with an Accord with the I4 on several different boards. No one reports anything better than 34-35 MPG's under ideal driving conditions (speed). I was driving aggressively. Spent several hours on the road when I was forced to slow down to 80 MPH, and tried to stay near 95 MPH if I could. I am impressed with my findings.

Originally Posted By: tig1
One question: Why use an oil that's thicker than your engine calls for? I use only 0-20. Can't see a need for anything heavier. Just wondering.


I personally believe the 30 weight oil is giving my engine slightly better protection. It's just my personal belief. I have no proof. Plus, there are times when this car sees 6k RPM's on the highway or surface streets if I get a bit too aggressive.

I don't think the thicker oil is hurting anything. I think it "might" provide a more effective barrier preventing metal-to-metal contact. Perhaps.

 

[gregk24]

Is it still under warranty? If it is then you should not be using a 30 weight, if not then its your car, do what you want. I have an 06 Accord with the K24, I run Pennzoil Platinum 0w20 in it as I do many many short trips per day and it rarely gets up to temp. To each there own.

 

[crazyoildude]

5w20 gets to the top of the engine faster than the 30 that has been proven by a lot of r&d
on the same note i dont think 30 will hurt it but i believe 20 is better

 

[buster]

It's very hard to measure small changes in mpg. Generally speaking, the lower the HT/HS the greater the fuel economy.

 

[Shannow]

Originally Posted By: crazyoildude
5w20 gets to the top of the engine faster than the 30 that has been proven by a lot of r&d


Really ?

show me...

 

[Clevy]

Originally Posted By: crazyoildude
5w20 gets to the top of the engine faster than the 30 that has been proven by a lot of r&d
on the same note i dont think 30 will hurt it but i believe 20 is better



Really? Where can I find this R&D info.

My charger just got liqui-moly 0w-40 and a quart of Pennzoil Platinum 0w20,with a can of cera-tec. Previous fill was Mobil 1 5w-20.
So given that I diluted 5 litres of 0w-40 with a litre of 0w-20 I will guesstimate that the oil in my sump is a heavy 30 grade. Fuel consumption hasn't changed that I've noticed in the 400 miles I've driven since the change.
Winter is coming so I wanted a slightly thicker oil in the sump to compensate for the inevitable fuel dilution I will get because of the inevitable longer idling times the vehicle will experience over winter.
I'm confident that an engine will consume less fuel when using a thinner oil based on there being less parasitic loss however it seems to me that any fuel consumption savings is barely perceptible in most day to day driving and most people won't notice any fuel consumption changes.
I can say that my motor is running 10f cooler with this thicker mix in the sump. I can also feel the engine is less free spinning now compared to before the oil change.
The engine seemed to rev a bit faster with 5w-20,and there is enough of a change for me to notice immediately. However under load at full throttle it almost feels like its pulling harder. Engine braking using the gears feels more pronounced now as well as compared to before. Almost like there is more drag.
Its possible that since I didn't use mos2 in this oil fill it could be wearing off thereby the co-efficient of friction may be increasing as the mos2 plating wears off but I assume I'd see that reflected in fuel consumption as well.
Or it could be happening so slowly that I'm not noticing the fuel consumption increase and as the miles accumulate I'll see the miles per tank reduce.
Or it could just be the oil is thicker and requires more energy to pump which would also increase drag.
Just thought I'd add my observations since I just went 2 grades thicker than the previous fill and I noticed some minor operational differences.

 

[Merkava_4]

Those Honda engines are probably loud on 0W-20. A 5w30 would probably quiet them down some.

 

[Shannow]

Originally Posted By: Clevy
Or it could just be the oil is thicker and requires more energy to pump which would also increase drag.


Been through this before...oil pump power has virtually no difference between grades, and certainly not from a 20 thickened a tad with 0W-40.

You can honestly save more turning off your headlights than oil pump drive power between viscosity grades.

 

[Clevy]

Originally Posted By: Shannow
Originally Posted By: Clevy
Or it could just be the oil is thicker and requires more energy to pump which would also increase drag.


Been through this before...oil pump power has virtually no difference between grades, and certainly not from a 20 thickened a tad with 0W-40.

You can honestly save more turning off your headlights than oil pump drive power between viscosity grades.


I'm beginning to believe you as far as drag and fuel economy is concerned in respect to thicker oils.
I expected to see at least some form of fuel consumption increase however that just doesn't seem to be the case.
And just to clarify I used 5 litres of 0w-40 and a single quart of 0w-20.
It's becoming clearer to me that in practice, on the open road the grade of oil in an engine really is only a tiny factor in relation to fuel economy.
The theory behind thin oils does make absolute sense however in practice its barely a perceptible variable so it seems.

 

[Shannow]

Clevy,
I was referring to the OPs thickened 0W-20...

nevertheless, the gains in the lighter weights are due to bearing frictional losses (albeit, at a reduced bearing film thickness), not pumping losses.

As JHZR2 pointed out quite correctly, you and I won't see the difference tank to tank, but in standardised testing, over millions of vehicles, it adds up corporately

 

[Sonataman]

Over the course of two summers, March to September, I now have data on the same oil, Pennzoil conventional, in two grades, 10w30 and 5w20.

My oil change dates are 3/1 and 9/1 and in 2012 during the OCI from 3/1 to 9/1 with Pennzoil conventional10w30 I averaged 42.58 mpg.

2013 during the same OCI timeline with Pennzoil conventional5w20 I averaged 44.48 mpg.

All calculations are manual and my driving patterns are boringly consistent.

 

[Cujet]

I tried both the Mobil 1 Advanced Fuel Economy oils 0w-20 and 0w30 in my 2.5L Jaguar X-Type w/manual transmission. I did not experience more MPG, or a better, free-er running engine. Overall, I'd say my experiment was a failure. As not only did my MPG or power not improve, but my oil consumption increased markedly.

However, this engine has adjustable cam timing, and the use of a slightly higher viscosity results in more accurate cam timing.

My engine clearly prefers 5W-40 and gets it's best MPG, about 27MPG, mixed driving with that oil. It's more responsive with more viscosity. Once again, possibly due to the cam phasers operating more accurately, and certainly due to better ring seal.

 

[surfstar]

At speeds of 95 mph, I wonder if that 5w30 was closer to a 20wt anyways?

On my previous car, I achieved my highest MPG on two tanks while running Pennzoil Conventional. Did I conclude that dino gave better MPG than synthetic?
No! One data point is not a valid comparison.

All we can take away from this thread is that that Accord achieved the observed MPG while running whatever oil was in it. We can't compare it to anything else. The title is very misleading and quite wrong.

 

[Shannow]

Originally Posted By: surfstar
At speeds of 95 mph, I wonder if that 5w30 was closer to a 20wt anyways?


What sort of a statement is THAT ?

No it was closer to a 30 weight because it WAS a 30 weight, to be a 20 weight it has to be a 20 weight. If you are saying that at 95MPH it had thinned some, that could be correct, but it's still a 30. And a 20 would have been thinner still