87 vs 91 fuel mpg differance?

[1Raider]

Has anyone really noticed any difference in mpg's with the different fuel grades? I've been getting high 12's on 87 and just fueled up with some 91.
Just was wondering if it was worth it to use the higher octane fuel.

 

[Sooliman]

Interestingly enough....I just filled the past two tanks with 93, and while I don't notice any difference whatsoever in performance or the way the truck runs (didn't knock or ping with 87), I am getting slightly improved fuel economy. Was around 13.5, now getting low 15s. I haven't changed my driving habits or city vs. hwy driving either. So......I keep questioning myself as to whether or not the it's the fuel, or just the truck starting to break-in a bit. I have just over 1600 miles. I have noticed the ECO light coming on more frequently / sooner with the higher octane gas, but it could all be subjective or coincidence, or again just breaking in. Curious to know your findings!

 

[Zinger]

The experts will tell you it's not related to the octane.

I'll tell you that even if it was, you got 10% better economy at a cost of 20% extra per gallon. Not a win.

 

[Sooliman]

The experts will tell you it's not related to the octane.

I'll tell you that even if it was, you got 10% better economy at a cost of 20% extra per gallon. Not a win.

Fair.....and accurate math. But......15.2 feels so much better than 13.5....somewhere around 30% better, I'd say.

 

[kjn86]

I got 2 MPG better with 89. I also feel like I am somehow giving my truck something less than ideal now with 87 mentally, like it's putting dirty gas in there! I will stick with 89. I was doing the math though on the price difference versus the fuel saving difference and it's a wash, or certainly so close as to not be worth debating.

 

[Gondul]

I like playing around with this website:
Fuel Cost Calculator

I'm going to run premium for a bit to see what happens, I can get premium cheaper at Costco than I can get midgrade anywhere else in town.

These were the numbers I ran and figured I'd be out a couple of bucks in 6 months if it is a wash... I would still use a TOP TIER, vs the uber cheap stuff.

++++++++++++++++++++++++++++++++++++++++
87 Octane is $2.04 at my local Costco
15mpg would make a 500 mile trip $68.00 and 33.33 gallons

91 Octane is $2.35 at my local Costco
17mpg would make a 500 mile trip $69.12 and 29.14 gallons

*BUT*
If you can get the MPG up by one more
18mpg would make a 500 mile trip $65.28 and 27.78 gallons

*OR*
If the price difference were closer to .20 cents, $2.25 vs $2.35
17MPG would make a 500 mile trip $66.18 and 29.41 gallons

 

[Zinger]

I like playing around with this website:
Fuel Cost Calculator

I'm going to run premium for a bit to see what happens, I can get premium cheaper at Costco than I can get midgrade anywhere else in town.

These were the numbers I ran and figured I'd be out a couple of bucks in 6 months if it is a wash... I would still use a TOP TIER, vs the uber cheap stuff.

++++++++++++++++++++++++++++++++++++++++
87 Octane is $2.04 at my local Costco
15mpg would make a 500 mile trip $68.00 and 33.33 gallons

91 Octane is $2.35 at my local Costco
17mpg would make a 500 mile trip $69.12 and 29.14 gallons

*BUT*
If you can get the MPG up by one more
18mpg would make a 500 mile trip $65.28 and 27.78 gallons

*OR*
If the price difference were closer to .20 cents, $2.25 vs $2.35
17MPG would make a 500 mile trip $66.18 and 29.41 gallons

I fill up with Costco gas 90% of the time, basically whenever I have the option that's where I go. As you say, they only sell 87 and 91, so I think my Ram is getting 87 by default. At least it's Top-Tier 87!

I'll probably throw some 91 in before I tow my camper, but otherwise I think 87 is what I'll be running.

 

[Sooliman]

I got 2 MPG better with 89. I also feel like I am somehow giving my truck something less than ideal now with 87 mentally, like it's putting dirty gas in there! I will stick with 89. I was doing the math though on the price difference versus the fuel saving difference and it's a wash, or certainly so close as to not be worth debating.

That's two votes for 2 mpgs more with higher octane......
Like @Gondul said....it's a wash for cost ultimately, but its interesting that other folks are confirming what I'm seeing with the uptick....again, could all be coincidence.

 

[Gman]

I ran into the issue tonight when I stopped at Costco. They had 85...or 91. I'd prefer to use 87 (mid-grade), but it wasn't available, so the new truck got 91. I don't think it will change the price of tea, as I'm still at less than 1K miles and break-in will have more of an affect than anything.

 

[dutchman187]

I'm currently tracking a tank of 91 versus my last 3 with 87. As of now, I'm a solid 2.5 increase in mpg halfway through the tank. 89 without ethanol is not an option where I live, so it is 87 or 91.

 

[Daniel]

Has anyone really noticed any difference in mpg's with the different fuel grades? I've been getting high 12's on 87 and just fueled up with some 91.
Just was wondering if it was worth it to use the higher octane fuel.

Yep out of your wallet

 

[AnthonyD1978]

Yep out of your wallet

I would generally agree with you, but I just noticed in the owners manual it does state 89 will give you better MPG over 87. Same for 91?

 

[Gman]

Once you're compressed fuel is stable, what value do you get for making it more stable than required?

The recommendation for best performance and fuel economy in the manual is using a "Plus" grade. That doesn't mean "Premium".

There is no assurance in the manual that you will get better MPG.

...but it's your money, spend it where you want.

One of the best bits of info on fuel selection in the manual is this;

Besides using unleaded gasoline with the proper octane rating, gasolines that contain detergents, corrosion and stability additives are recommended. Using gasolines that have these additives will help improve fuel economy, reduce emissions, and maintain vehicle performance.

Designated TOP TIER Detergent Gasoline contains a higher level of detergents to further aide in minimizing engine and fuel system deposits. When available, the usage of TOP TIER Detergent gasoline is recommended. Visit www.toptiergas.com for a list of TOP TIER Detergent Gasoline Retailers.

 

[KRField]

I noticed a 2mpg a good decrease on two tanks of 87 and no difference between 89 and 91 two tanks each.


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[Gondul]

Yes, the Premium is likely overkill, but for me it is a good .20¢ *cheaper* at Costco than Midgrade anywhere else... and Costco does sell TOP TIER gas.

I know what my target #s are for this experiment... I'm willing to spend and extra .20¢ a gallon through a couple of tanks to see if there is a difference.

 

[Zinger]

Yes, the Premium is likely overkill, but for me it is a good .20¢ *cheaper* at Costco than Midgrade anywhere else... and Costco does sell TOP TIER gas.

I know what my target #s are for this experiment... I'm willing to spend and extra .20¢ a gallon through a couple of tanks to see if there is a difference.

I was thinking this over as I do the Costco thing as well. I do believe next tank I'm going to split the tank between the two grades to get 89!

 

[Gondul]

I was thinking this over as I do the Costco thing as well. I do believe next tank I'm going to split the tank between the two grades to get 89!

Well, that's what they do at the gas stations... looking at the math, that about $5 'saved' if you do 50/50... provided you know exactly how much gas to put in...

 

[KRField]

Yes, the Premium is likely overkill, but for me it is a good .20¢ *cheaper* at Costco than Midgrade anywhere else... and Costco does sell TOP TIER gas.

I know what my target #s are for this experiment... I'm willing to spend and extra .20¢ a gallon through a couple of tanks to see if there is a difference.

Top tier is also key when filling up. I did not know Costco supplied top tier.


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[Zinger]

Well, that's what they do at the gas stations... looking at the math, that about $5 'saved' if you do 50/50... provided you know exactly how much gas to put in...

Is there a "gallons used" metric in the info center somewhere? If so, it should be close enough to calculate the split easily.

 

[Zinger]

Top tier is also key when filling up. I did not know Costco supplied top tier.


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Yep, and they roll so many cars through there (at least the one I go to) it's practically guaranteed to be fresh.