5.7 Hemi - 87 or 89 Octane

[Cueva del Osos]

What rearend ratio do you have (don't see a Signature Block on your post?) That makes a difference as well. (compare 3.21 versus 3.92.)
3.21 would get better mileage at say 80 compared to the 3.92 (because the 3.21 RPMs would be lower .. HOWEVER, one also needs to know what RPMs their engine powerband is and Cruising RPMs as well to know which axle ratio you choose. There are plenty of online calculators for helping one decide. Most choose the 3.92 for trailer towing to get them off the line. I chose the 3.21 since I do not tow and plan on making trips back home a few times a year.

Tim N

I’ve got the 3.92 axle, Ltd, etorque crew cab. Suppose I’ll get around to the signature block sooner or later.

Just to clarify, I wasn’t bellyaching about the mileage drop with increased speed or about the axle ratio, just commenting on it. I WAS complaining about the poor results provided by certain brands of fuel - whether by refinery design or by station owner practices.

We all know faster costs more...just seems that the hemi consumption curve is steeper than previous vehicles I’ve owned. Again, not complaining, i really like this truck...I just use this aspect to help keep my own driving at a balance of speed, performance and cost that works best for me.

 

[Diamondback]

I’ve got the 3.92 axle, Ltd, etorque crew cab. Suppose I’ll get around to the signature block sooner or later.

Just to clarify, I wasn’t bellyaching about the mileage drop with increased speed or about the axle ratio, just commenting on it. I WAS complaining about the poor results provided by certain brands of fuel - whether by refinery design or by station owner practices.

We all know faster costs more...just seems that the hemi consumption curve is steeper than previous vehicles I’ve owned. Again, not complaining, i really like this truck...I just use this aspect to help keep my own driving at a balance of speed, performance and cost that works best for me.

Not bashing at all, just wanted to know to compare. I have the Standard Hemi with 3.21 .. I'll be doing a 100 mile drive test today to empty out the last tank I filled up with to fill up with 91 on the return trip home.

Maybe I'll get to do some 0-60 pulls and recordings with the DT. I need to call a few deputies to see who is on duty and tell them my plan in case they get calls about a Gray Ram Truck Racing around LOL

Tim N

 

[StuartV]

I ran 89 in my truck for about 7000 miles. End of last week I changed to 87 and did a road trip over the weekend. About 700 miles. So far, just based on the lie-o-meter, I don't see any noticeable difference. But, I don't really have enough driving on 87 yet to really draw any conclusions.

I just know that over the first 7000-ish miles, I have averaged 14.5 MPG on 89. The next few thousand on 87 will really tell the tale for me.

 

[kevinssaco]

Indeed , not the way you drive. It has made a difference the past four or so tank fulls for my driving experience, why I posted.

I didn't get an extra 2mpg switching from 87 to 89 but I did get about 1.4 mpg. Thats 26 extra miles per 20 gal tank at a .20 price difference from 87 to 89 thats about $3.91. It cost about $4 more to fill the tank so its close to a wash but considering the smoother ride and MDS transition I'll keep going with 89 from now on.

 

[rah6887]

Non ethanol 87 for me

 

[Rob5589]

Interestingly, I ran my first tank of 89. With my usual driving I dropped from about 18.5-19 ave to 17.1. I just filled up today again with 89 to see if it was a fluke.

Second tank of 89, 19.1. First tank must have been a fluke.

 

[Ken Robbins]

I'm sure you've probably considered it, but when I fill up at Costco, I blend the 91 with the 87 to get to 89, or close to it. Saves some $ and really no additional benefit to using all 91 that I am aware of.

That's how 99% of gas stations today mix 87 to 91(93) octane at the pumps to get 89 octane. You'll only find white painted lids in the ground for 87 octane, red for 91 octane & yellow for diesel. Some older stations get 89 octane straight from the rack, which you'll find a blue lid in the ground with the others. But most of these older stations all have updated their pumps today and it gets mixed at the pump.
I only put 89 octane from Sunoco in my tank. I used to deliver Costco's gas, most guys don't drain their previous compartment dry before reloading. Which means when the hose empties when your dropping in the ground, your done. When you get back to the rack, your supposed to drain the compartment into 5 gallon buckets until it's 100% empty. I'd estimate about 90% of drivers don't fully drain their compartments before loading a different gas or fuel on top. Why, because it takes to much time and nobody will ever know.

Sheetz drivers will get written up if they don't drain their compartments, so I'll use them if there's no Sunoco near by. Sunoco has their own drivers and they're good. I stay away from the gas stations that aren't a true Sunoco, but they use/sell Sunoco branded gas, but the gas deliveries are contracted out and not delivered by Sunoco drivers. If they don't have a Sunoco sign on their building as their main name and only at the pumps and the road, it's not owned by Sunoco. I'm very picky about my gas. lol

 

[Ken Robbins]

That's how 99% of gas stations today mix 87 to 91(93) octane at the pumps to get 89 octane. You'll only find white painted lids in the ground for 87 octane, red for 91 octane & yellow for diesel. Some older stations get 89 octane straight from the rack, which you'll find a blue lid in the ground with the others. But most of these older stations all have updated their pumps today and it gets mixed at the pump.
I only put 89 octane from Sunoco in my tank. I used to deliver Costco's gas, most guys don't drain their previous compartment dry before reloading. Which means when the hose empties when your dropping in the ground, your done. When you get back to the rack, your supposed to drain the compartment into 5 gallon buckets until it's 100% empty. I'd estimate about 90% of drivers don't fully drain their compartments before loading a different gas or fuel on top. Why, because it takes to much time and nobody will ever know.

Sheetz drivers will get written up if they don't drain their compartments, so I'll use them if there's no Sunoco near by. Sunoco has their own drivers and they're good. I stay away from the gas stations that aren't a true Sunoco, but they use/sell Sunoco branded gas, but the gas deliveries are contracted out and not delivered by Sunoco drivers. If they don't have a Sunoco sign on their building as their main name and only at the pumps and the road, it's not owned by Sunoco. I'm very picky about my gas. lol

They mix regular and premium (different octane levels of premium). Been a long night.

 

[Jako]

I'm sure you've probably considered it, but when I fill up at Costco, I blend the 91 with the 87 to get to 89, or close to it. Saves some $ and really no additional benefit to using all 91 that I am aware of.

Costcos near me pump 87 and 93 so it is the 1/3 2/3 math. I find the price of 87 is pretty similar from Costco to Costco but 93 can vary. I believe my savings by blending at Costco is about 20 cents a gallon or better over 89 stations. About $130 savings over 11,000+ miles at .20/gallon. Not huge but it paid for the Coverking rear neoprene black/charcoal seat covers.

 

[RedRocketZ28]

I've noticed absolutely no difference in 87 vs 89. Both with 10% ethanol. I have 13,800 miles on my truck now and it's had a trailer (boat or car trailer) hooked to it for probably 6,000 of those miles. No difference in power or mpg running either octane. My truck now gets whatever is cheapest at the gas station I stop at (except for E85 of course).

 

[Jako]

Four 390 mile trips, 2 with 89, 1 with 91, 1 with 87 octane.

Jan. 17, 2019, odom 2,351 miles, original oil, 89 octane - 20.62
Mar. 16, 2019, odom 4,581 miles, Penzoil PUP, 89 octane - 20.87
May 19, 2019, odom 6,997 miles, Penzoil PUP, 91 octane - 22.38
Nov. 30, 2019, odom 11,948 miles, Penzoil PUP, 87 octane - 19.82
Bighorm 18" OEM wheels all trips.
Best MPG has been 22.54 with 89 octane on a 198.9 mile trip. Similar but not exact terrain (some miles same). Currently there are 12,395 miles on the odometer with an average of 16.73 mpg.

All hand calculated. I do not believe my driving habits changed on the 87 octane trip. I often/usually fill up at Costco where I blend 87 and 93 octane to 89 (+ mostly, - sometimes/rarely) when I can. The 87 octane was from a Quick Chek in NJ. $2.359 was hard to pass up and I wanted to test the mpg with 87 octane.

I draw no conclusion at this point. More data to come as I have a few more trips before my son graduates college.

I include the date, vehicle miles, engine oil and tires for those who would like to extrapolate some conclusion.

Anyone with similar experiences?

 

[eyeguy]

Four 390 mile trips, 2 with 89, 1 with 91, 1 with 87 octane.

Jan. 17, 2019, odom 2,351 miles, original oil, 89 octane - 20.62
Mar. 16, 2019, odom 4,581 miles, Penzoil PUP, 89 octane - 20.87
May 19, 2019, odom 6,997 miles, Penzoil PUP, 91 octane - 22.38
Nov. 30, 2019, odom 11,948 miles, Penzoil PUP, 87 octane - 19.82
Bighorm 18" OEM wheels all trips.
Best MPG has been 22.54 with 89 octane on a 198.9 mile trip. Similar but not exact terrain (some miles same). Currently there are 12,395 miles on the odometer with an average of 16.73 mpg.

All hand calculated. I do not believe my driving habits changed on the 87 octane trip. I often/usually fill up at Costco where I blend 87 and 93 octane to 89 (+ mostly, - sometimes/rarely) when I can. The 87 octane was from a Quick Chek in NJ. $2.359 was hard to pass up and I wanted to test the mpg with 87 octane.

I draw no conclusion at this point. More data to come as I have a few more trips before my son graduates college.

I include the date, vehicle miles, engine oil and tires for those who would like to extrapolate some conclusion.

Anyone with similar experiences?

Outside temperature would be an interesting addition to your listed info.

 

[Wakesnowb]

Manual states 89 Octane so thats the gas my truck gets. My MPG is pretty crappy at just over 13 mpg with 7000 miles on the truck but whatever.

 

[JJRamTX]

The standard gas here in Colorado at 6500+ feet altitude is 85 octane and that is what costco carries which seems to give the same mileage up at this altitude as 91. I have seen better fuel economy at lower altitudes with higher octane though, especially at less than 500 feet above sea level.

 

[Jako]

Outside temperature would be an interesting addition to your listed info.

I was shooting from the hip with the info. Weather (temperature/humidity) does have an effect on motor performance.
I know my motorcycles have a noticeable improvement in performance in the cooler weather. The motorcycles are about 600 lbs. so a little improvement in performance is probably more readily felt than in our Rams. Hopefully I will be able to run the tank down before I go so I can try 91 again otherwise it will be 89. It doesn't matter the results as I follow the manufacturer's recommendation of 89.
Tire pressure even comes into play as per the manual:
"The tire pressure will vary with temperature by about 1 psi (7 kPa) for every 12°F (6.5°C). This means that when the outside temperature decreases, the tire pressure will decrease."
I had set the tires 2 psi higher because it was 60 degrees that day and the I figured 30-40 degrees is probably a better temperature to set the tire pressure to the vehicle specs this time of year.

Thanks for the suggestion - you got me thinking, add a temperature column to my mpg sheet! But than I need to know winter gas . This could turn into a science project.
What is the ideal weather (degrees/humidity) for the 5.7L hemi to get peak performance? Any gear heads out there?

 

[NDanecker]

I usually run 87 or 89 but since I'm doing some extreme motor mods in a week or 2 I have been filling with 93 to flush out the lower octane fuel in the tank. All I can say - wow. Not sure if the ECM is slowly reprogramming the fuel mapping and/or timing because of detonation with the lower octane fuel but the truck runs MUCH better with 93. Wasn't noticeable right away as it started around the 2 and 3rd tank. By 4th tank it was noticeable. Truck is not as lethargic.

Disclaimer - all tests done using a butt-dyno. LOL

 

[silver billet]

Ethanol makes a noticable difference for me. Local station sells without any ethanol. Runs much better without, which was a shock and unexpected because my previous ride with the v6 pentastar it was complete opposite, I always avoided this station with my Jeep but was in a hurry and out of gas so tried it few months ago in my truck. Now I avoid the stations I used to use and always fill up local.