Fuel economy observation. 0W-20 vs 5W-30

[Ded Mazai]

I have run a 5W-30 oil in my Subaru BRZ for the past 30000 km. And decided to see if I can save any fuel by switching to the recommended 0W-20. I use the same road every day so my average fuel consumption reading was almost exactly the same every week: 7.0 to 7.1 litres per 100 km. I was hoping to get maybe 6.9. Not a chance. Still 7.0 to 7.1. Likely I won't use a 0W-20 any more.

 

[Quattro Pete]

While the change in fuel economy may be real as a result of change in HT/HS viscosity, it is typically too small to be detected, especially when there are so many other factors out of your control that can affect it.

 

[friendly_jacek]

it depends how you drive it. if you start it in cold weather and only drive a couple of km at slow speeds, there could be a significant difference. but if you drive it at high speeds long distances in warm weather, there should be hardly a difference at all.

 

[geeman789]

Mobil states that a 0.2 to a 2.3 % improvement can be expected when using M1 AFE compared to "higher viscosity..." oil.

Real world interpretation...

Virtually undetectable to a very, very small improvement in fuel economy.... no miracles with "slippery..." oil.

Pump up your tires, minimize idling, use AC only when needed, and drive smart... only THEN will you see a noticeable improvement in fuel economy. Driving style is a HUGE factor in determining fuel economy.

 

[OneEyeJack]

I tested this EPA mileage claim with a company car a few years ago, a 0w-20 vs a 5w-30. Both oils were PP purchased from Wally World. 98% of the trips were on the cruise control, long commutes. I drove late at night or very early in the morning, no traffic either way. With over a year on that job there was no statistical difference. I changed the oil at 3K miles because that was company policy, not to be violated under any circumstances, ever. I ran 3 oil change intervals on each oil and put just under 44K miles on the car. I don't have my records but I think I changed the oil about 15 times because it was 5 cycles on each viscosity of oil. I only changed the Mobil 1 filter when I changed viscosity at 9k miles. The car was started up and always run at least 100 miles each work day.

The car was a second generation Prius. I was the only driver. This proves absolutely nothing but was at least is was interesting. I just don't buy everything that comes from the EPA about this viscosity stuff because it's a government organization with absolutely no oversight and answers to no one. When they speak the only acceptable answers are "yes, boss, anything you say boss, of course boss and right away boss, and please, please, please forgive me for breathing or going to the toilet or turning on the lights at night or using the a/c or driving a car, or existing at all".

 

[splinter]

Originally Posted By: geeman789
Mobil states that a 0.2 to a 2.3 % improvement can be expected when using M1 AFE compared to "higher viscosity.." oil....

I've read that 'disclaimer' and similar disclosures from other trustworthy "fuel saving" lubricant refiners.

There might be something to be eked out but fretting over a few additional dollars in fuel expenses is not a high priority for me and mine. Yet.

 

[stranger706]

A couple years ago I tried a few different oils in my old Mazda 3 over a few months on my work commute. I could not tell a difference between M1 0w20, PP 5w30, Valvoline 10w30. The difference was smaller than my normal tank to tank variation. This was during mild/warm weather.

Not until I poured in some Rotella T6 5w40 could I tell a difference. That finally did it alright. Made the engine more sluggish, used up some hp and the mpg were consistently lower. About 1-2 mpg lower on a mostly hwy/interstate commute.

I think the only time 0w20 makes a difference is on short commutes or cold weather.

 

[buck91]

Subjective "SOTP" (seat of the pants) difference with the last OCI in the Olds 3.5L. Switched from 5w30 QSUD to 10w30 Rotella T and the engine feels ever so slighly less peppy. I suspect I lost about 1mpg highway also, but thats estimated on observations and not by analyzing hard records.

 

[chrisri]

I tried 10w60 in my Alfa when was tracking the car. Compared with 5w40 consumption surely went up, and motor was less responsive.
There is a difference, but to see one we would need a laboratory conditions.

 

[Shannow]

Taken to the extremes, you will notice differences.

Going from an SAE30 one summer to a 25W70 in my old J-Car wagon, the cranking was slower, it was very much more sluggish, and used considerably more fuel (didn't blow up, even at -7c).

5W20 to 20W60 in my mower give about a 10C difference in oil temperature due to increased drag.

Honda claim that the reason for their uber VII is to maximise economy in the warm-up part of the vehicle operation.

 

[Garak]

Originally Posted By: geeman789
Virtually undetectable to a very, very small improvement in fuel economy.... no miracles with "slippery..." oil.

You know how it is. Driving habits can easily exceed that 2.3%, not to mention switches in fuel blends, the weather, traffic....

Mobil and OEMs are well equipped to figure out fuel savings. We may enjoy the benefits, but we'll never be able to measure the difference ourselves, unless it's a monumental switch in lubricants, like Shannow mentioned.

 

[Bamaro]

Unless its a double blind test/comparison, results will be suspect.

 

[FutureDoc]

There are enough variable for the average consumer, IDing those MPGs from viscosity alone is nearly impossible... but that does not mean it does not exist. The trick is the 2% which needs nearly lab capacity to find.

First, unless you have an accurate way of gauging ACTUAL fuel consumption, you can't really measure anything. Those MPG onboard calculators are often 5%+/- so 2% is lost in the inaccuracy of the computer. Heck, if you have a late 2000s Honda, those thing can be +/-30%. Eeeek. Those onboard MPG readouts are more about post-purchase customer marketing. If you bought a Chrysler V6 and are getting 27mpg on the dash, you go "good golly" this get good mpg and feel good about it and hopefully you will buy another. BUT, if you take fuel receipts and compare miles per fill-up... which happens to be 23-24mpg, then maybe not. Manufacturers were notorious (and still are) about making their onboard fuel calculators very optimistic.

Next, you will need to account for ambient temp, weight, fuel blends/density, wind direction, surface conditions, etc which all could be over a 2% difference.

The US consumed 137 billion gallons. If you saved 2% or 2.75 billion gallons, that is significant to the grand scheme although impacts on the consumer is minimal.

Yes, it is a "search for a frog-hair" type of engineering feat. I don't see 0w20 offering anything less than other oil as far as engine longevity. Will it hurt to run thicker? No. But if everything is a wash, those 2.75 billion gallons are best saved.

 

[NO2]

If you live in Russia, especially the northern part, Siberia or the mountains, I would use a 0w-20 because of your extremely cold winters. You will get a little better start up protection in the winter, a little less strain on your battery and starter, and greater peace of mind that you won't be stranded.

 

[Koz1]

I notice it, I have a very light foot and try to coast every where.

 

[gfh77665]

I will take a car filled with 20-50 and fully inflated tires, over the same car filled with 0-20 with even moderate under inflation in the tires (similar to what people typically drive around on) and win the MPG game each day and every day!

 

[Merkava_4]

Originally Posted By: buck91
Subjective "SOTP" (seat of the pants) difference with the last OCI in the Olds 3.5L. Switched from 5w30 QSUD to 10w30 Rotella T and the engine feels ever so slighly less peppy. I suspect I lost about 1mpg highway also, but thats estimated on observations and not by analyzing hard records.


A more level comparison would have been QSUD 5W-30 to QSUD 10W-30.

 

[Marisa]

IMO the 0w20 oil is like the sealed transmissions, designed to keep you buying new cars. I remember in Germany a 0w20 was an engine flush lol. The only other good use for it may be in racing little japanese engines like a motorcycle engine. At the end of the day you can't go by the manufacturers recommendations or this site wouldn't exist. I remember I had a 2007 Audi Cabriolet, heavy(2 tons) with an overworked 2.0T that always needed to be on boost, even had it reflashed for an extra 50hp and was still slow passing a semi. Anyway the motor used oil right away and the dealer was saying to change the oil every 10k miles with a 0w40. I do believe in start up protection so I don't mind a 0w, but the 40 was obviously not reducing the oil consumption, so I found the Eneos EN-0W50 and what do you know, oil consumption stopped between 5k mile changes. Funny thing is it's the #1 oil in Japan! lol

 

[Clevy]

Originally Posted By: Marisa
IMO the 0w20 oil is like the sealed transmissions, designed to keep you buying new cars. I remember in Germany a 0w20 was an engine flush lol. The only other good use for it may be in racing little japanese engines like a motorcycle engine. At the end of the day you can't go by the manufacturers recommendations or this site wouldn't exist. I remember I had a 2007 Audi Cabriolet, heavy(2 tons) with an overworked 2.0T that always needed to be on boost, even had it reflashed for an extra 50hp and was still slow passing a semi. Anyway the motor used oil right away and the dealer was saying to change the oil every 10k miles with a 0w40. I do believe in start up protection so I don't mind a 0w, but the 40 was obviously not reducing the oil consumption, so I found the Eneos EN-0W50 and what do you know, oil consumption stopped between 5k mile changes. Funny thing is it's the #1 oil in Japan! lol


Absolutely absurd.

It's amazing what people can convince themselves into believing.

 

[Marisa]

Originally Posted By: Clevy
Originally Posted By: Marisa
IMO the 0w20 oil is like the sealed transmissions, designed to keep you buying new cars. I remember in Germany a 0w20 was an engine flush lol. The only other good use for it may be in racing little japanese engines like a motorcycle engine. At the end of the day you can't go by the manufacturers recommendations or this site wouldn't exist. I remember I had a 2007 Audi Cabriolet, heavy(2 tons) with an overworked 2.0T that always needed to be on boost, even had it reflashed for an extra 50hp and was still slow passing a semi. Anyway the motor used oil right away and the dealer was saying to change the oil every 10k miles with a 0w40. I do believe in start up protection so I don't mind a 0w, but the 40 was obviously not reducing the oil consumption, so I found the Eneos EN-0W50 and what do you know, oil consumption stopped between 5k mile changes. Funny thing is it's the #1 oil in Japan! lol


Absolutely absurd.

It's amazing what people can convince themselves into believing.


The dipstick doesn't lie, no pun intended.