Myth or Fact: Synthetic Increases MPG

[Jason64]

Will a Synthetic Oil (Group III or higher) really get better MPG than a conventional oil?

(Assuming they are both the same grade (e.g. 5w30), same API cert (e.g. SN), 5000mile OCI, and both have the Resource Conserving tag.)


Jason

 

[Quattro Pete]

Once they're both at operating temp, I'd say myth.

But if the synthetic one has better cold flow properties, then it could potentially improve fuel economy before the engine reaches operating temp. Even if so, the difference would be minimal, IMO.

 

[Jason64]

I had my doubts too. If you google hypermiling synthetic the hypermilers seem to recommend synthetic.

 

[cp3]

I think it's possible but so minimal it would be hard to prove outside of controled testing.

 

[NightRiderQ45]

Not enough to even think twice about the subject! Cold oil flow, extended oci's...go with syn. 5-6k oci's, stick with dino.

 

[CATERHAM]

I agree.
I would also add that synthetic oils generally have higher viscosity index's than dino oils, and sometimes dramatically higher particularly with 0W-20 oils and that alone will contribute to the oil being more fuel efficient.

Also many GP V based syn' oils do have lower coefficients of friction which can contribute to better fuel economy. And many contain higher levels of AW additives which can improve fuel economy.

So the answer really is it depends on the particular syn' oil your talking about.

 

[chubbs1]

The differences are so minimal it is hard to even make a good call on that one. Also, driving conditions change and are hard to make a good control to test theory.

 

[friendly_jacek]

There still could be a difference as viscosity could vary a lot within the same grade. Ie: SAE 30 ranges from 9-12 cst @100C. That is a huge range.

If one controls for viscosity difference, the only difference could be in VI and the only circumstances I can think of that could possibly show MPG difference would be very cold starts and short trips. There should be no difference at hwy speeds or even a slight loss of MPG if HTHS is higher.

 

[09_GXP]

Fact! I don't have the paper handy but a University did a study and showed synthetic with a ~2% mpg advantage over dino oil.

 

[Jason64]

Thank you. So it's really about the wear and friction-reducing additives rather than the base oil, with the possible exception of Grp Vs.

 

[aquariuscsm]

Myth. Imo the only advantage to synth oil is that it`s cleaner(won`t warnish ot sludge up your engine).

 

[mtxjohn]

Fact. http://www.fuelly.com/driver/mtxjohn/rsx

People who actually track their fuel usage will tell you to they experience a significant increase with synthetic. I am beating the EPA by about 50% with my car. Synthetic saves me money. Saves me time. I have 177,000 on my rsx and wifey has 270,000 on her crv. Saves me the cost of buying a new car. Its a [censored] no-brainer. But there are a lot of morons out there trying to save a few pennies at oil change and spending a LOT MORE on gas.

 

[Ken2]

Originally Posted By: 09_GXP
Fact! I don't have the paper handy but a University did a study and showed synthetic with a ~2% mpg advantage over dino oil.

I've heard the same from people who've run a truck on a dyno---2 to 3%. Not enough to alone pay for the syn oil, but added to extended drain intervals, reduced filter cost, and reduced oil change labor, a money saver in total.

 

[TMoto]

Sounds like a project for Mythbusters.

 

[CATERHAM]

Originally Posted By: Jason64
Thank you. So it's really about the wear and friction-reducing additives rather than the base oil, with the possible exception of Grp Vs.

Yes except higher VI oils use lighter base oils so they have an advantage there.
The answer is you can't generalize you must look at the actual oils in question. In fact there are some 5W-30 dinos that have higher VI's and better add pac's than some cheap 5W-30 synthetics.

What you can say, is that the most fuel efficient oils are synthetic but simply being labelled as synthetic doesn't make an oil more fuel efficient.

 

[volk06]

 

[oldmaninsc]

Originally Posted By: 09_GXP
Fact! I don't have the paper handy but a University did a study and showed synthetic with a ~2% mpg advantage over dino oil.

I agree - on my Aerostar I used Valvoline Syn. sometimes and other times used Valvoline white bottle over the course of 200K miles. On long trips I THOUGHT I noticed a 1/2 MPG increase when using Syn. but figured there were too many other variables to say one way or another.
The same has been true on my other cars.

 

[JOD]

GIII and GIV base oils have a lower CoF, so all else equal, a synthetic oil will provide better fuel economy.

As mentioned though, all else normally isn't equal... Viscosity, both at start-up and in operation, along with friction modifiers also factor into the equation. Here's power point which gives an overview of some of the studies on it: http://www.atiel.org/members/pdf_files/Gp III Conoco Bell.pdf

Truth is though, I think the gains to be had are pretty small--and fuel economy really doesn't factor into my lubricant choice. At the macro level, it may make a difference, on the individual level it'll be a minimal difference.

 

[Quattro Pete]

Originally Posted By: oldmaninsc
but figured there were too many other variables to say one way or another.

And there are way too many other variables at play to be able to detect and attribute a 1/2 mpg change directly to oil.

 

[Oregoonian]

Originally Posted By: mtxjohn
Fact. http://www.fuelly.com/driver/mtxjohn/rsx

People who actually track their fuel usage will tell you to they experience a significant increase with synthetic. I am beating the EPA by about 50% with my car. Synthetic saves me money. Saves me time. I have 177,000 on my rsx and wifey has 270,000 on her crv. Saves me the cost of buying a new car. Its a [censored] no-brainer. But there are a lot of morons out there trying to save a few pennies at oil change and spending a LOT MORE on gas.
Originally Posted By: Ken2
Originally Posted By: 09_GXP
Fact! I don't have the paper handy but a University did a study and showed synthetic with a ~2% mpg advantage over dino oil.

I've heard the same from people who've run a truck on a dyno---2 to 3%. Not enough to alone pay for the syn oil, but added to extended drain intervals, reduced filter cost, and reduced oil change labor, a money saver in total.
Originally Posted By: Ken2
Originally Posted By: 09_GXP
Fact! I don't have the paper handy but a University did a study and showed synthetic with a ~2% mpg advantage over dino oil.

I've heard the same from people who've run a truck on a dyno---2 to 3%. Not enough to alone pay for the syn oil, but added to extended drain intervals, reduced filter cost, and reduced oil change labor, a money saver in total.


+1....2 to 3% fuel savings....plus all the other advantages of synthetic (i.e. Better cold starts..thus less wear, longer OCI's,hold up better in high heat etc. etc.) In addition, the price of dino is getting closer to syn every month or so.

Using syn for 30% longer OCI's....plus a slight increase in mpg....IMO...makes syn the way to go...and the cost would be close to the same.