Octane change??

[IrishRED]

I have been very consistently running 93 octane fuel in my Ram. However, with prices on the rise, I am considering dropping to 87 ( I go to a gas station where the only choices are 87 or 93). I know 89 is recommended but has anyone noticed a downside to 87 and should I expect any issues if I have been running 93 for the first 12000+ miles then suddenly drop to 87?

 

[kdoublep]

Lots of discussion on this. Some have no problem using 87. I use 89 all the time since I bought my truck 1 year ago. It is also available at all gas stations around me. I thought about going to 87 due to prices too but decided I'll just stick with 89.

 

[brenan00]

I have been very consistently running 93 octane fuel in my Ram. However, with prices on the rise, I am considering dropping to 87 ( I go to a gas station where the only choices are 87 or 93). I know 89 is recommended but has anyone noticed a downside to 87 and should I expect any issues if I have been running 93 for the first 12000+ miles then suddenly drop to 87?

Go half and half and make your own 90. That is what I do, and our costco is no corn.

 

[JC4041]

I've been tuned for 87 for a few years now.....I have seen some saying not to, I may go back to the 89 tune soon....depends on gas prices.

 

[SD Rebel]

Costco premium, usually cheaper than the 87 of regular stations.

 

[Oldphart]

I don't think I would run 87 in anything unless it's non-ethanol. Been running 91 non-ethanol since new. Around here, it's a few cents cheaper than 93 corn. Been getting 18-19 in mostly backroad driving with the MDS off. I think it would do 1 or 2 mpg better if I left it functional.

 

[Andymax]

No issues running 87. Yesterday drove from Dayton OH to Charlotte NC...Average 20.98 Hand Calculated. MANY run 87 with no issues. Some get knock. Some stick with recommended 89. Some simply prefer 89+. Manual clearly states 87 is OK.

 

[GKIII]

I run 89 for two reasons:

1. The few times I've run 87 I've heard a light knock.
2. I run under high load often enough (towing) that planning around 87 vs 89 would be a major pain in the ***.

 

[Vol4Life]

I've run 87 since the day I bought my 2021 (New Year's Eve last year). Never noticed any issues and drives like a dream. Never tried running a higher octane to see if it runs any better since it runs so good as is. The sales guy I dealt with said most customers he's sold them to all run 87, also.

 

[Shots]

89 is only "recommended" for optimal performance. I ran 89 in mine the first few fills (and exclusively on my 4th gen). Chatting with a guy at the dealership, he told me that the free tank they give you when you buy the truck is filled with 87. Likewise the gas they put in it until it sells is 87. I didn't feel, or hear any difference with that first tank so I figured why not give it a shot. If it's good enough for the dealership its good enough for me. I've been running 87 for multiple tanks since then with no noticeable difference.
That said I drive like an old man, and I don't haul/tow heavy very often. On those trips I'd run 89 to get the most out of the engine, but for general driving and light loads, 87 is just fine.

 

[Timeless]

Pretty much been answered it seems. Stick to 89 or higher if under heavy load...otherwise 87 is fine for light duty driving.

As someone mentioned above, Sams/Costco 93 premium is typically close to 87 and cheaper than 89 at other stations. I do the mix method as well with tanks of regular and premium alternating.

 

[Orion10182011]

I run 89 for two reasons:

1. The few times I've run 87 I've heard a light knock.
2. I run under high load often enough (towing) that planning around 87 vs 89 would be a major pain in the ***.

It always floors me when people say they have heard knock. I've seen it on data logs and heard it in old cars I used to have but never on anything newer.

Makes me wonder if the knock sensor is bad or the problem has gotten so bad it's beyone the ability of the knock sensors to retard it out.

 

[Orion10182011]

OP, you will be fine changing octane. There is a long term knock table in the ECU that may take some time to adjust when you go back up in octane. Defiantly run higher grades when towing or running the engine hard.

Just cursing around you will lose a bit of power and MPG from timing being pulled by the ECU when running low grade.

 

[IrishRED]

Thank you all for the input!!

 

[Shots]

Just cursing around you will lose a bit of power and MPG from timing being pulled by the ECU when running low grade.

Efficiency does go down a hair but not too bad. I lost about 1 mpg by switching to 87, and I don't fee a performance difference at all

Some people worry about the mpg loss of using 87. I was one of them so I did some math. I posted the following calculations in another thread, but here it is again in case anyone interested hasn't seen it.

If 89 cost $0.30 more than 87 (which is average here), how much better mpg do you have to get to offset the cost?

Octane	Cost per gal	mpg	miles	gallons used	Cost of trip
89	2.80	20.00	300	15.00	$42.00	actual	highway
87	2.50	17.85	300	16.80	$42.00	break even calc	highway
89	2.80	17.50	300	17.14	$47.99	actual	city
87	2.50	15.63	300	19.19	$47.99	break even calc	city

In the above chart I used 300 miles for a "trip."
I was averaging 20 mpg on the freeway and 17.5 around town when running 89. To figure out if 87 was less cost effective I calculated what my mpg would have to be to cost the same (or worse).
I highlighted the calculated values in red to show where the break-even point is. If I use 87 and lose more than about 2 mpg I'm actually better off running 89.
I am currently averaging 16.7 around town, and that's with the slightly bigger tires, and lift/level. So that 0.8 mpg loss may not be entirely a result of the octane change. Even if it is, I'm still well ahead of the break even mark. No reason at all for me to run 89.
Just something to consider.

**Note added after a road trip December 1, 2021: I'm averaging 19.0 on the freeway.

 

[Glenn54]

I went from 89 to 87 after gas prices increased. No change in performance or MPG. Before some clown starts yaking about, it's a truck and you shouldn't have purchased it for the gas mileage, I'm retired and on fixed income. Every damn thing is going up so I have to adjust expenses some way.

 

[Jack.]

I'm currently running costco premium aswell, I've been actually contemplating on switching back to Costco 87 just because I don't tow or anything. 9/10 time it's just for cruising from job site to job sites (put in about 3k miles a month) and the 1/10 time with Lumber and etc in the bed.

With the increase of gas recently I think 87 might be the way to go

 

[Glenn54]

Thanks for bringing up towing, Jack. I will be towing a travel trailer about 3,000 miles next week. I may compare Regular to Plus and see if there is a difference in performance or MPG.

 

[Mountain Whiskey]

Yep. This guy changed to 87. See what happens?