The higher Octane Dispute

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

jamestaylor47

Senior Member
Joined
May 14, 2012
Posts
292
Reaction score
15
Location
OKIE
Ram Year
2011
Engine
5.7L Hemi
Well my fellow ram owners, I am here to ask the question that it seems no matter where I go I get a different answer. So I'm asking this live to see if real time people who have tried it and if it really is worth messing with or just a big marketing scam.

"Does higher octane improve gas mileage as well as engine quality?"

I've always been an 87 regular octane guy myself, but in my four wheeler I've always ran highest octane I can get, but overall for a 5.7 hemi is it financially worth the extra few cents per gallon? I drive 50 mile round trip to work and back 6 days a week so any long period fuel saving would be beneficial.

Thanks


Sent from my iPhone using Tapatalk
 

Dubstep Shep

Senior Member
Joined
Aug 4, 2014
Posts
2,240
Reaction score
513
Location
Houston
Ram Year
2014 R/T
Engine
5.7L Hemi
In short, no. It will not save you any money.

Look at it like this:
The lowest regular gas price (87 oct) near me is about $2.45 a gallon.
The lowest premium gas price (93 oct) near me is about $2.79 a gallon.

So if currently you get "X" miles per gallon, that means you're getting "X/2.45" miles per dollar. For that number to even stay the same, you would have to get "2.79*X/2.45" or "1.1389X" MPG on the premium fuel. So if you're getting 20mpg on regular fuel, you'd have to be getting 22.78MPG on premium. And there's no way you're going to pick up almost 14% MPG off of four octane points without changing anything but timing.
 
Last edited:

DiabeticKripple

Senior Member
Joined
Jan 9, 2015
Posts
267
Reaction score
44
Location
Calgary / Grande Prairie, Alberta
Ram Year
2014
Engine
Hemi 5.7L
The truck is supposed to run on 89. Any higher you are wasting money, lower you don't get the power.

I put 87 in mine cause I drive all highway and it saves me $10/tank.
 

jayhuc

Member
Joined
Oct 5, 2013
Posts
40
Reaction score
22
Location
Toronto
Ram Year
2011
Engine
hemi 5.7
Unless you have a tuner. Higher octane wont do anything. Higher octane has a higher tolerance for detonation. But the stock programming will change timing to prevent knock (detonation @ the wrong time). With a tuner, you can change this setting.

So in short , NO. You could put race fuel in and it wont do a thing for performance or mpg.

Just wait... Now you must ask yourself. ethanol or pure gas... Thats where you can makeup some mpg with stock tuning.
 

Graygoose

Indecisive Car Owner
Supporting Member
Joined
Nov 21, 2011
Posts
16,824
Reaction score
31,460
Location
Oklahoma
Ram Year
Convert, for now.
Engine
small
87 is fine, 89 is the sweet spot. Sure you can save $5.00 per fill up and worry about detonation when you have to pull or pass someone, or splurge $5.00 per fill up and go ahead and get 89. Anything higher without mods to support it is a waste.
 

Seraphim38

Member
Joined
Jul 13, 2015
Posts
32
Reaction score
7
Ram Year
2007
Engine
5.7 gas
I just bought a new Dodge Ram Mega Cab on Friday, so I am new to this board.

I race everything I can get my hands on, and have a lot of experience tuning.

To answer the original question; the octane of the fuel comes into play relative to fuel mixture and timing. If your engine is tuned to operate on fuel that has a higher octane rating than what you use in real life, then under load if you engine computer registers detonation via knock sensor it will reduce engine timing to prevent engine damage. That means you will loose power. Given the dynamic state of the motor, as rpm and load are constantly changing, by the time the ECU pulls timing you may have already passed beyond the conditions that triggered the reduction in the first place.

If you run a higher octane of fuel than that which your engine is tuned for, you are throwing money away. It does you absolutely no good because your engine is not configured to leverage the added octane.

I have configured my personal performance vehicles with compression ratios and timing curves that are optimized for 92 up to 116. My last car put out 250rwhp per liter of engine displacement on 92 pump gas (Garrett GTX turbo helped). Yup, that would be almost 1500 horsepower on a Hemi displacement motor with only pump gas. I don't plan on building my new truck though; I am going to use it to pull my race trailer ;)
 

Bombdigitty

Senior Member
Joined
Jun 21, 2013
Posts
143
Reaction score
40
Ram Year
2010
Engine
Hemi 5.7
I tested this when I bought my truck and again about a month ago.

I always run 89. I dropped to 87 for 1 tank. Kept driving habbits the same.
I got 50km less from the tank during both tests.

Here gas is about 1.17(87) 1.25(89) per liter right now. I get on average about 14.9-16.3 L per 100 km.

Therefore spending the extra 5-10 bucks at fill up time saves me about $15 overall.

I think I did all that math right....
 

LoneStarHemi

Member
Joined
Jun 2, 2014
Posts
53
Reaction score
16
Ram Year
2014 RAM 1500
Engine
Hemi 5.7
I’ve read a few other threads with mixed results about 87 vs 89 and my limited testing seemed to be inconclusive when you throw in driving habits so, I wasn’t sure. I decided to take another approach. These hemi’s seem to have a poorly baffled pcv location so adding a catch can will help maintain fuel octane by preventing the pcv from sending that oil to the intake. Also, I added a 180 t-stat to keep the engine cooler. Next will be a vararam for a cold air intake. So I make those efforts for a cooler denser air/fuel mixture and just run the the 87 ****. :cool:
 

SlowRoller

Senior Member
Joined
Apr 21, 2015
Posts
925
Reaction score
280
Ram Year
2014
Engine
5.7
87 for normal driving is perfectly fine. Sometimes, I'll spring for 89 if I'm loaded/pulling, or dreaming of another 1/10 or 2 of a mpg during a bonafide trip,,.

Zero/zip/nada benefit for anything above 89 with OEM tuning.
 

crazy_luck

Senior Member
Joined
Nov 9, 2014
Posts
1,127
Reaction score
784
Location
Minnesota
Ram Year
2013
Engine
5.7
Typically, I fill up to a full tank every time and I usually fill up when the needle is between 1/2 and 3/8 left - about 15 gallons - I always fill up with 89 which is 10 cents more than 87, which is a whopping $1.50 more per fill-up. The few times I use the 93 (with no ethanol) at a local station when I run some carbon cleaner through the tank, it's a whopping $2.20 more per tank... Considering I fill up 2 times a week, I'm out $3.00 more than I would be if I used 87...
 

Limeybastard

Senior Member
Joined
Jul 25, 2015
Posts
1,872
Reaction score
449
Location
Shady Hills, Rednecksville Boro, Florida.
Ram Year
2015
Engine
Hemi 5.7
Im just quite content with filling with 87 at the moment, may try 89 sometimes for shnitz and giggles.

This is coming from a person that was ***** at the pump since his vehicles during the last 5 years or so commanded Premium. Lifes Good.. (now) well sort off.
 
Last edited:

crazzywolfie

Senior Member
Joined
Apr 6, 2013
Posts
16,422
Reaction score
3,183
Location
under the truck
Ram Year
81 93
Engine
5.2
if the higher octane gas is ethanol free like they sell at all shell gas stations up here you would most likely see some difference in fuel mileage.
 

B-Shot

Senior Member
Joined
Aug 11, 2014
Posts
207
Reaction score
50
Ram Year
2012
Engine
5.7
I loose about 1.5mpg on 87 and get the same on 89 and 93 but better throttle response on 93. If I use non ethanol 87 I get the same mpg as 89 w/ethanol .just my observation on my truck over 2 years now.
 

preachp

Senior Member
Joined
Dec 8, 2013
Posts
522
Reaction score
177
Location
The Con State (CT)
Ram Year
2013
Engine
5.7 Hemi
Hi Op,

Higher the octane slower the burn. High octane is needed for high compression to avoid detonation. It does this by slowing the burn time down for the fuel charge. It can in the right circumstances increase the amount of energy the charge creates. Does it help with mileage probably not, but then you would have to decide that for yourself.
So higher octane slower burn, lower octane faster burn.
Have a great day,

preachp
 

Dubstep Shep

Senior Member
Joined
Aug 4, 2014
Posts
2,240
Reaction score
513
Location
Houston
Ram Year
2014 R/T
Engine
5.7L Hemi
Hi Op,

Higher the octane slower the burn. High octane is needed for high compression to avoid detonation. It does this by slowing the burn time down for the fuel charge. It can in the right circumstances increase the amount of energy the charge creates. Does it help with mileage probably not, but then you would have to decide that for yourself.
So higher octane slower burn, lower octane faster burn.
Have a great day,

preachp

Bingo.

In other words, unless you run a tune that requires higher octane, you actually may get worse gas mileage on higher octane.
 

Graygoose

Indecisive Car Owner
Supporting Member
Joined
Nov 21, 2011
Posts
16,824
Reaction score
31,460
Location
Oklahoma
Ram Year
Convert, for now.
Engine
small
Correct, too high like 93, you could go backwards and lose money at the pump.
 

craigsez

Senior Member
Joined
Aug 24, 2012
Posts
1,063
Reaction score
376
Location
Novascotia,Canada
Ram Year
2016
Engine
5.7
I tested this when I bought my truck and again about a month ago.

I always run 89. I dropped to 87 for 1 tank. Kept driving habbits the same.
I got 50km less from the tank during both tests.

Here gas is about 1.17(87) 1.25(89) per liter right now. I get on average about 14.9-16.3 L per 100 km.

Therefore spending the extra 5-10 bucks at fill up time saves me about $15 overall.

I think I did all that math right....

50 k less on a take could have been cause of a few factors..
Wind...
Temps....
humidity...
weight in truck....
quality of the batch of fuel from that gas station..
who was driveing and how hard or easy they are on the peddle..
road conditions...ect ect ect..

In any case op..No sence in buyin higher octane fuel if your truck/car/bike/lawn mower/weed wacker/girlfriends ***** is tuned from factory for a specific octane...
 

crazzywolfie

Senior Member
Joined
Apr 6, 2013
Posts
16,422
Reaction score
3,183
Location
under the truck
Ram Year
81 93
Engine
5.2
In any case op..No sence in buyin higher octane fuel if your truck/car/bike/lawn mower/weed wacker/girlfriends ***** is tuned from factory for a specific octane...
you must like having to pay someone to fix stuff for you. you would never catch anything less than ethanol free 91 octane gas in my lawn mowers, weed wackers, snow blowers and in my truck especially this time of year. i have dealt with ethanol poisoning in too many carbed engines to run cheap gas in them.
IMG_2994.jpg
took less than 6 months of ethanol to create this mess in my 81's carb
188224_10151502801016672_571529570_n.jpg
 

Latest posts

Forum statistics

Threads
194,925
Posts
2,864,164
Members
155,293
Latest member
RedFlameRam
Top