Does grade REALLY effect fuel economy???

[WMSmotorhead]

This isn't precise science, but I think it's pretty interesting to think about.

My work car is a 2001 Ford Focus with the 4-cyl Zetec engine.
I've been driving this car for 9 years.
The car calls for 5w-20...
When I first got it, (2004), 5w-20 was not common on shelves.. so I was putting 5w30 in it. When 5w-20 became easily available in a store brand, I used that. Last year, I hit a major buy-out, filling my shelves with 5w-20, 5w30, and 10w30


I started putting the 5w30 back in the Focus, since it was the most plentiful on the shelf. Recently, since it's summer, I started putting the 10w30 in it instead.

Each time I fuel the car, I reset the trip odometer.. I run the car until the fuel is quite low... then fill the tank full.

I take the figure on the fuel pump (usually aprox 12 gallons) and see how far I went on it via the trip odometer.

When I first got the car, 27mpg was a normal calculation. Now, with more time/miles, the figure is consistently at 30mpg. The last tank was 31mpg. (with 10w30 in the engine).

There's a huge deal of hype surrounding 5w-20 giving engines better fuel economy, but from what I can tell by my own experience, the effects are minimal. When the weather gets cold, I'll likely go back to the 5w stuff... since I'm just aiming to use up the 10w30 whilst it is hot outside.

Since everyone loves to know brands and stuff...
5w-20 is a WPP/WNE made product (varies)
5w30 was Wolf's head
10w-30 was either Wolf's Head or Mag1 (wpp/wne)

My conclusion is that the oil I put in this engine has a minimal effect on the fuel economy of it.

 

[silverrat]

Minimal gains are worth it for them

 

[JOD]

Originally Posted By: WMSmotorhead


There's a huge deal of hype surrounding 5w-20 giving engines better fuel economy....
My conclusion is that the oil I put in this engine has a minimal effect on the fuel economy of it.


While the "hype" may be huge, the actual claimed gains are small. All else equal, lighter oils have less drag and are going to be more efficient; but internal engine friction is a very small part of the overall equation. Your tires losing tread, lower air density from warmer air, traffic patterns, less-efficient winter gas... all of that stuff plays a role. Again, it doesn't mean the gains from a more fuel efficient lubricant don't exist, it just means that they're small and difficult to measure.

 

[SwampSurvivor]

Marginally.

 

[A_Harman]

You've put your finger on the fallacy of fuel-efficient oils. Yes, thinner oils save fuel, but conscientious people such as yourself can't prove it with the low precision of the instruments they have available. To get the API Fuel Conserving stamp, a 5w20 has to demonstrate that it saves 1.2% over a 10w40 reference oil after an aging period of 100 hours. Likewise, a 5w30 has to show a 0.9% improvement over the same 10w40, and a 10w30 has to show 0.6% improvement.

So if you're comparing a 5w20 to a 10w30, you should only expect to see a fuel economy improvement of 0.6%, all other factors being equal. If your car gets 30 mpg on 10w30, then you would expect to see 30.18 mpg with 5w20 if you could control your daily driving routine consistently enough, and measure fuel consumption with laboratory grade instruments. The REAL WORLD being what it is thwarts such attempts at precision outside of a laboratory. Maybe you sit in traffic jams for 30 minutes more on one tank of fuel than the previous, or the weather is warmer, making you run the AC more.

 

[Donald]

I think only a vehicle in a lab enroronment with a flow meter and very accurate measure miles, etc would see the difference. And it will be marginal.

But getting 1/10 of a mile better for CAFE could be important if you are GM and sell millions of cars.

 

[Smokescreen]

In a lab they can control every variable, temperatures, wind resistance, perfect tire psi...everything.

In real life, any single variable can skew results...slight breeze, road surface, temperatures, tire pressure fluctuation due to ambient temperatures. I probably have the most controlled commute of any one I know and any environmental elemant can affect results.

In real life I can assure you 5w20 vs 5w30 conventional/syn no matter...will not make a lick of difference. Maybe at -40C/-40F but that is about it.

 

[CATERHAM]

Originally Posted By: Donald

But getting 1/10 of a mile better for CAFE could be important if you are GM and sell millions of cars.

As has been eloquently explained the fuel savings is a lot more than that, so why understate it?

How you drive your vehicle can make a significant difference.
If it's primarily long distance highway mileage the savings will be minimized, but if one does a lot of short commutes particularly in colder weather then the savings in using a light high VI oil can be very noticeable.

I couldn't care less about CAFE but I run the light high VI oils for the performance and drivability benefits on start-up and during the warming up period. The fuel savings are an incidental benefit.

 

[MajorCavalry]

Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve

 

[OVERKILL]

Originally Posted By: MajorCavalry
Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve


Ummm, it should be, it is a much heavier oil........

 

[needsducktape]

If you really want to to save gas drive less, accelerate softly and don't speed. Keep an eye on tire pressure and wheel alignment.

Changing weights of oil in order to save gas is like being overweight and expecting Diet Coke to solve your problem.

 

[MajorCavalry]

Originally Posted By: OVERKILL
Originally Posted By: MajorCavalry
Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve


Ummm, it should be, it is a much heavier oil........


I would have thought at ambient temp, both are 5W oils thus the viscosity should be similar.

 

[94astro]

Originally Posted By: needsducktape
If you really want to to save gas drive less, accelerate softly and don't speed. Keep an eye on tire pressure and wheel alignment.

Changing weights of oil in order to save gas is like being overweight and expecting Diet Coke to solve your problem.


This

 

[kschachn]

No not necessarily.

Originally Posted By: MajorCavalry
I would have thought at ambient temp, both are 5W oils thus the viscosity should be similar.

 

[A_Harman]

Originally Posted By: OVERKILL
Originally Posted By: MajorCavalry
Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve


Ummm, it should be, it is a much heavier oil........


Yes. This is the part of the discussion where it needs to be mentioned that the HTHS viscosity is the parameter that has actually been proven to correlate with fuel economy. 30-weights can vary in HTHS over a range of about 20% (2.9 to 3.5 cP), so there actually can be some difference in fuel economy between heavy and light 30's.

 

[WMSmotorhead]

Right.... The biggest impact I have been able to see in my experience is fuel grade... Super grade fuel goes farther between fill-ups, and with a wholesale club membership and various other discount programs, I can keep the $ per mile on par with other fuels. Thus, I run super in all my cars and enjoy the better running engines.

Based on my experience, the best way to save gas is to buy high test, and drive wisely.

I did find it interesting that there's so much buzz about so little effect /w/ motor oils.

In regards to the car's performance, I observe insignificant changes in perceived performance from grade to grade also. I highly doubt that 10w30 will have any harmful effects on this motor in the summer months.

Humorously, I have some 0w-20 Amsoil that I got along with the closeouts ($2.50 a bottle)... I wonder what that'd do.... I guess not much.

 

[ARCOgraphite]

Originally Posted By: kschachn
What?

Originally Posted By: MajorCavalry
I would have thought at ambient temp, both are 5W oils thus the viscosity should be similar.


Right! Wrong!

The winter (W) rating (0/5/10/15 or 20) is measured for spec way below zero -30 and -35c for 0w and 5w; which is dang! cold.

SAE 30 or 20 grading is measured at "STP Boiling" and any typical "ambient" temp is not a spec but must be interpolated from VI and KV100 or KV40/kv100.

I suppose Kv40, which is measured around 104F - which seems to be ambient "parking lot temp" for my commute home these days - could be roughly considered a hot summer ambient. Within Kv40 A xxW20 grade measures about 45-50cSt and xxW30 around 55-65cSt (range taken off the top of my thick skull).
Here's a some SAE CCS spec you can see in nice chart form at the PQI America webpage:

Cold Crank Viscosity
Low temperature viscosity (mPa∙s) Max (CCS)
0W 6200 @ -35
5W 6600 @ -30
10W 7000 @ -25
15W 7000 @ -20
20W 9500 @ -15
25W 13000 @ -10

 

[OVERKILL]

Originally Posted By: MajorCavalry
Originally Posted By: OVERKILL
Originally Posted By: MajorCavalry
Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve


Ummm, it should be, it is a much heavier oil........


I would have thought at ambient temp, both are 5W oils thus the viscosity should be similar.


That's not how the grading system works.

The 5w is just the measure of the oil's cold performance, it means it falls within the range for a 5w-xx lubricant, which means a maximum of 6600cP @ -30C.

http://www.pqiamerica.com/Testdescriptions/Coldcrank25.html

The oils you are comparing are extremely different.

For example:

Pennzoil Platinum 5w-20:
@ 40C: 45.34cSt
@ 100C: 8.56cSt
HTHS: 2.6cP
CCS: 3,860 @ -30C
MRV: 11,100 @ -35C

Mobil 1 ESP 5w30:
@ 40C: 72.8cSt
@ 100C: 12.1cSt
HTHS: 3.58cP
CCS: N/A
MRV: N/A

So at 40C (a touch above ambient) the ESP 5w30 is almost twice as thick as the Pennzoil Platinum 5w-20.

 

[OVERKILL]

Originally Posted By: A_Harman
Originally Posted By: OVERKILL
Originally Posted By: MajorCavalry
Certainly unscientific, but when using 5W-20 oil (Pennzoil Platinum, Pennzoil Ultra, Mobil 1) I averaged 20.5 mpg over each oil change interval. My last oil change was Mobil 1 European formula 5w30 ESP since it was on sale. Over the last 1600 miles my MPG has averaged 19.3. My driving style has not changed. I have been perhaps more careful with the go pedal now that I see a drecrease in mileage.

I honestly did not expect to see any difference. Also, quite unscientifically, the Mobil 1 5w30 appears much more viscous when pouring new oil from the bottle.

Steve


Ummm, it should be, it is a much heavier oil........


Yes. This is the part of the discussion where it needs to be mentioned that the HTHS viscosity is the parameter that has actually been proven to correlate with fuel economy. 30-weights can vary in HTHS over a range of about 20% (2.9 to 3.5 cP), so there actually can be some difference in fuel economy between heavy and light 30's.


And this particular oil, being a Euro-spec oil makes that difference even more pronounced, as it has an HTHS of 3.58cP.

 

[needsducktape]

This all sounds like splitting hairs when you consider the original poster's comments regarding FUEL ECONOMY.

For an Individual the biggest factors are: the left foot, tire pressure, alignment, clean fuel/air filters, spark plugs etc etc

Now spread out over many of cars- If I had a fleet: Yes, I would consider the variations among 30wt, 20wt and so on.