Premium vs regular gas

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.

Elkman

Senior Member
Joined
Aug 21, 2018
Posts
672
Reaction score
328
Location
Monterey
Ram Year
2019
Engine
V6
E15 is not gasoline so much as a subsidizing of Archer Daniels Midland profits. Figure a 25-30% reduction in fuel economy.

I am surprised that Octane Rating which has been around for nearly a century is not understood by 99% of the people buying gasoline at the pump. Octane is a measure of resistance to pre-ignition and nothing more.

The higher the compression ratio of the engine the higher the octane rated fuel that is needed to provide maximum power without pre-ignition which will damage the engine. If an engine is designed to use 93 octane rated gasoline is instead fed 87 octane rated gasoline, vehicles made in the last 30 years with their electronic ignitiion will simply retard the spark and no problem. A 10% reduction in miles per gallon but no damage to the engine.

Now if the engine is designed to use 87 octane rated gasoline and someone pumps 93 octane rated gasoline into the fuel tank then that will help the profits of the gas station but do absolutely nothing for the performance of the engine or prolong its life.

Higher octane rated gasoline has the same btu's available to power the engine as regular gas at the pumps. It is only when ethanol is added to the mix that the available btu's from a gallon of fuel drops.

Plenty of people ready to help the gullible spend more money on their vehicles. A friend of my wife was conned by the tire store where they convinced her to put "nitrogen" in her new tires at an additional cost. They failed to mention and the women did not know is that air is 80% nitrogen already and no measurable difference between 100% nitrogen and 80% nitrogen mix in tire performance or life. The devil is in the details but one has to take the time to think in a critical manner which seldom happens.
 

Atcer2018

Senior Member
Military
Joined
Aug 10, 2019
Posts
949
Reaction score
1,188
Location
Virginia
Ram Year
2018
Engine
3.6
E15 is not gasoline so much as a subsidizing of Archer Daniels Midland profits. Figure a 25-30% reduction in fuel economy.
Do flex fuel vehicles see less of a reduction in fuel economy using E15? I have a flex fuel Pentastar and I’ve only used E15 three times. All three times were purchased on the Pennsylvania Turnpike at the start of a 400 mile all highway trip from my sisters home back to southeastern VA. I saw maybe a mile decrease per gallon via the computer readout. It’s not sold where I live so I have no other experience with it other than 60 mph with cruise control on most of the time.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,806
Reaction score
17,091
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Superb (factual) rant, @Elkman , thank you.

So many people who don't know what they're talking about getting online and rambling to get attention, instead of just asking and learning. Sad.
 

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
I have seen fuel prices (locally) rise from $3.50 a gallon to almost $6.70 a gallon that is for premium rated 91 octane with 10% ethanol top tier gasoline.



The same gas station has a dedicated pump for zero ethanol fuel that is rated at 93 octane that was consistently priced at $5.00 a gallon, and now sells for about $6.50 a gallon.



Anyone with engineering or simple physics experience can point out that alcohol burns cleaner with less carbon by the amount of soot or smoke produced with open flame.

Alcohol also burns hotter but produces less energy than petroleum based fuel.



The hotter you can burn a fuel the more energy you can use (extract) in the form of combustion producing motion of mechanical assemblies.



This isn’t a discussion on what type of fuel but what octane, so I will not go into diesel versus CNG or Hydrogen.



Combustion and mechanical motion produces friction and inevitable wear.

The less heat and radiation from friction and the combustion cycle , the less wear will be evident in the mechanical assemblies subjected to it.



From this reasoning and knowledge I logically purchase the zero ethanol 93 octane at a $1.50 increase than to purchase a less efficient 91 octane adulterated fuel that has increased in price by $3.50 a gallon.



My driving habits have been modified to accept the reality of our economic shortcomings and although I can achieve a higher rate of acceleration in a less stressful combustion environment, (in this scenario) in order to benefit from the increased efficiency, I still need to measure self control on the gas pedal.
 

Tray Burge

Senior Member
Joined
Jul 30, 2015
Posts
2,242
Reaction score
2,334
Location
On the porch
Ram Year
2003
Engine
5.7 Hemi
It doesn't. I've gone to 89 as I've noticed enough of a fuel economy improvement vs 87 to offset the extra cost, but premium to 89 I notice no difference. As I understand it the engine management will adjust for 87 octane fuel, but will run at it's peak on 89 or better.
I always run 87, but can you actually feel any difference with the higher octane?
 

BWL

Embrace the skeptisism
Joined
Oct 14, 2017
Posts
8,528
Reaction score
8,464
Location
BC Canada
Ram Year
2017
Engine
hemi 5.7
I always run 87, but can you actually feel any difference with the higher octane?
I actually think I do, but the right foot dyno has a lot of margin for error. If it's setting back timing to adjust for 87 octane fuel it makes sense though. For me it's been mostly that my many trips in the past were closing in on 14l per 100 km with my best around 13.4 in ideal conditions and on 89 it's been 13 or just under consistently. Not much gain, but enough to offset the cost now at current prices. Figure if the price per mile is the same and I gain some range it's worth it. I ran 94 chevron for 1 trip and it was still in the same range I got on 89 in my early experimentation so it seems there is no benefit exceeding 89 in stock tune.
 

Docwagon1776

Senior Member
Military
Joined
Mar 16, 2012
Posts
2,177
Reaction score
3,565
Location
Midwest
Ram Year
2012, 2021
Engine
5.7, 6.4
I always run 87, but can you actually feel any difference with the higher octane?

If you're driving at reasonably legal speeds with light or no load, aren't in extreme heat, aren't flooring it off the line or passing with authority, probably not. If you're putting the motor under heavier loads, spiking combustion chamber temperatures, then you have a better chance of noticing the difference. Hence why you hear so many people who can't tell the difference. They could de-tune their truck by 20% and not notice a difference, either. The capabilities far exceed their needs. Which is awesome when you think about it, as this is how incredible modern trucks are compared to their counterparts of the 2000s and earlier.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,806
Reaction score
17,091
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Since I've been running 87 octane (10% ethanol) during this gas price spike, I too have noticed it doesn't run as well. Sputters some at idle and light load. This compared to 89 octane (10% ethanol) I used to run normally.

I speculate the ignition timing algorithm biases a bit too much toward r*e*t*a*r*ded timing as it senses knock, resulting in some partial combustion when lean.
 

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Even if the pump has a button for premium doesn’t necessarily mean that what’s going in your gas tank.

For me shift points are advanced and slightly less stressful with higher octane.
 
Joined
Nov 20, 2018
Posts
0
Reaction score
63
Location
Riverside California
Ram Year
2018 2wd
Engine
HEMI 5.7 Revolution 4.88s
In 107,000 miles i have used 87 all the time, never had a ping or lack of power. buying anything else is wasting $.
If you actually believe you've never had ping or lack of power on 87 then you are delusional .... unless you can prove it with logs that your truck never knocked on 87 you are flat out lying lol ...
 
Joined
Nov 20, 2018
Posts
0
Reaction score
63
Location
Riverside California
Ram Year
2018 2wd
Engine
HEMI 5.7 Revolution 4.88s
Since I've been running 87 octane (10% ethanol) during this gas price spike, I too have noticed it doesn't run as well. Sputters some at idle and light load. This compared to 89 octane (10% ethanol) I used to run normally.

I speculate the ignition timing algorithm biases a bit too much toward r*e*t*a*r*ded timing as it senses knock, resulting in some partial combustion when lean.
My truck will never get a drop of 87 in it regardless of gas prices lol ...

Like I posted in the other thread, I am going back to 91 because of the drop in MPG even though I don't really care about MPG but just reading and watching videos of the effects of 87 and 89 on these trucks even without a tune running 91 is just better for them ...

Also being that I have 37s with 4.88s running 91 makes a difference according to some random guy I ran into at the gas station a few weeks ago ..he asked me what I was running with the 37s and I told him 89 ...he said on his Ram with 37s he runs nothing but 91 without a tune and 4.56s though ....

So on a stock truck 89 should be fine but for my setup and actually coming across this topic more and more 91 on my truck is what I will be using from now on ....
 

1979PowerWagon360

Senior Member
Joined
Mar 19, 2019
Posts
306
Reaction score
385
Location
Central Florida
Ram Year
2022 TRX
Engine
6.2
As CheechDogg wrote, I don't believe you'll ever get knocking in a modern engine. I do believe all are equipped with a knock sensor and will retard the timing automatically in order to protect the engine. The manual recommends an octane for a reason. Mine states 89.
 
Joined
Nov 20, 2018
Posts
0
Reaction score
63
Location
Riverside California
Ram Year
2018 2wd
Engine
HEMI 5.7 Revolution 4.88s
As CheechDogg wrote, I don't believe you'll ever get knocking in a modern engine. I do believe all are equipped with a knock sensor and will retard the timing automatically in order to protect the engine. The manual recommends an octane for a reason. Mine states 89.
Yeah, these computers are so damn advanced that as soon as the notice the knocking they are going to adjust what it has to and "retard" the timing like you said ... but why would anyone want to allow that to happen by running 87 on these trucks is my question ... just to save a few dollars at the gas pump?

Nope not me, I loved my truck on 91 but on 89 the only big difference was the drop in MPG and a noticeable drop in power during WOT .... if I can avoid both of those by going back up to 91 then regardless of the price of gas I am doing it ....

Like I have said before, I have ran 91 in all my vehicles and even company ones, the ones we ran 89 and 87 eventually had issues and the ones running 91 zero issues ... my pops old hemi has never used anything but 91 and zero issues ...
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,806
Reaction score
17,091
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
My physics facts remain. Believe what you want.
 
Joined
Nov 20, 2018
Posts
0
Reaction score
63
Location
Riverside California
Ram Year
2018 2wd
Engine
HEMI 5.7 Revolution 4.88s
My physics facts remain. Believe what you want.
Physics facts? lol ..... Why get upset? lol

I believe what I have experienced simple as that ... just because owner's manual data ? Come on man lol ...

If and when I have to replace an engine in any of my vehicles due to the use of 91 then I will believe that running 91 is bad for these engines ... but I have yet to see that happen ... I don't think anyone on these forums has had to replace an engine or has had issues running 91 ... or have they? If they have can you post a link?

As a matter of fact, I have been told that a tune to run 91 is a waste of money unless you have other performance mods which I don't, so using 91 is perfectly fine ...

That believe what you want attitude wasn't necessary was it? My truck runs better on 91, better MPGs, uses all the power it can so why not run 91 ? lol ..
 

ramffml

Senior Member
Joined
Jul 12, 2019
Posts
2,773
Reaction score
5,017
Location
ramforum
Ram Year
2019
Engine
hemi 5.7
As CheechDogg wrote, I don't believe you'll ever get knocking in a modern engine. I do believe all are equipped with a knock sensor and will retard the timing automatically in order to protect the engine. The manual recommends an octane for a reason. Mine states 89.

That's true, but remember the knock sensor is basically a specialized microphone, and it is a reactive process. Meaning, the knock/ping occurs first, then the computer reacts by pulling timing. The sensors work by hearing the fact that it's pinging. You're still getting knock/ping, just less of it. Ideally you wouldn't need the sensors in the first place.
 

Oliver Closehauf

Senior Member
Joined
Nov 21, 2020
Posts
718
Reaction score
457
Location
Cincinnati
Ram Year
2005 Laramie
Engine
Cummins 5.9
I run premium always also. I can tell the difference. I can hear and feel the difference. If you want to run 87 in your vehicles I won't argue or try and talk you out of it. I run premium.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,806
Reaction score
17,091
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Yes, but the knock is very slight in the control feedback loop. When we think about knock, we're thinking of the audible rapping sound many of us have experienced. The knock sensors adjust timing way before that point.
 

ramffml

Senior Member
Joined
Jul 12, 2019
Posts
2,773
Reaction score
5,017
Location
ramforum
Ram Year
2019
Engine
hemi 5.7
Yes, but the knock is very slight in the control feedback loop. When we think about knock, we're thinking of the audible rapping sound many of us have experienced. The knock sensors adjust timing way before that point.

They must, yes, but it's not a perfect thing otherwise we wouldn't be able to still hear knock/pinging.

Despite having sensors and what I consider a brand new engine (< 20,000 miles) I still heard and continue to hear pinging.
 
Top