if the system calls for regular 87 use it .
if it requires 92 thats what you use,

If your vehicle 87spec requires the use of 92 for satisfactory performance REPAIR the issue it will be less expensive.

 

Premium vs. Regular

Have used both regular (87) and mid-grade (89) on my '18 5.7 Hemi. Have experienced no problems or have noticed no differences in either...Getting same mpg w/ both.

 

Have used both regular (87) and mid-grade (89) on my '18 5.7 Hemi. Have experienced no problems or have noticed no differences in either...Getting same mpg w/ both.

Same here. Our closest gas - Costco, has 87 or 92. I use to put in 92 for the Hemi since it cost the same as 89 at a real gas station. Did not notice a difference in mileage or response so I started using the 87. Owners manual says 87 is fine for the 5.7 most likely because the compression isn't high performance. Biggest thing is to have clean gas. And I run a can of Seafoam through about every six months.

 

WK2 Spec Sheet for the 5.7L motor states:

Compression Ratio: 10.5:1
Fuel Requirement: Unleaded mid-grade, 89 octane (R+M)/2 — recommended; unleaded regular, 87 octane (R+M)/2 — acceptable

FTR: I run COSTCO Premium (92)
Haven't tried the COSTCO 87 Octane, but I suppose it would be OK.

 

if 87 is OK why run COSTCO Premium (92).


Use 87 and send the money saved to a Veterans organization.

 

As I am a Veteran, I like the way you think!

 

No need no run any higher octane in the Jeep than what’s recommended. In fact the manual states, “the use of premium fuel is not recommended.” I’ve tried both 87 and 91 in my V8 and couldn’t tell a difference in performance or mileage. Nice to save a few $$’s with regular when you have to use premium in your other vehicles!

 

There are dozens of threads on this topic over the years.

There are production variances and fuel variances

There are heavy and light feet.

All make a difference. Lots of folks run 87 just fine. Lots of folks notice sharper throttle response and overall better running engine using 89. Few notice anything with 92 unless you have a tuner to take advantage. I have a good running motor, and it runs much smoother when filled with 89. My RAM has the 8 speed and it makes a subtle difference there to. If your engine is kind of a dog, you may not notice a thing as other factors are limiting.

The PCM sets engine timing based on a number of things, the more advanced the timing the better they run, but then there is the risk of pre-detonation events which are hard on an engine. So the PCM advances the timing until it starts seeing pre-events and pulls back a bit.. a lot for an event. Running 89 allows the timing to be advanced further and reduce the chance for a big timing pull... but many butt meters don't notice. It takes awhile, maybe a tank of fuel, for the PCM to complete adjustments, so its not something you'll notice immediately, so folks have a tendency to miss the benefits (if any).

That being said, it depends on the engine and your butt calibration, use what feels best for you, there is no right or wrong answer here


Oh, a tank from a busy gas station, with fresh fuel and low ethanol content, is going to run better than a tank from a quiet station with stale fuel and high moisture content, and you would notice that more than the 87/89 difference.

 

For almost 96K miles, I've used only 87 "regular" fuel in my 2012 Hemi equipped JGC. I have a light foot but never have noticed any issues whatsoever. 89 is "recommended, and I would use that for heavy towing, etc., but 87 is also acceptable according to the manual. Buying "premium" fuel is a waste of money, IMHO, unless you use a tuner and, well...tune it...so that the higher octane fuel can provide some benefit. Higher octane isn't about "power"...it's about preventing pre-detonation of fuel under high pressure. JGC's engine doesn't have that kind of high pressure.

 

I run Costco 87 on my '15 Hemi for daily driving. Higher octane if I need extra performance or towing.

 

Anyone have problems with the 85 octane "regular" gas they sell here in Denver for the 3.5? The 87 octane "mid grade" is significantly higher cost. I've read 85 works well at the mile high altitude but the manual says 87 period. I've used both grades and really don't notice a difference.

 

Seems like most don't grasp recommended vs acceptable LOL. Acceptable means in a pinch it is ok otherwise, you should be using recommended normally.

 

Agreed. I'm sure very few people look at octane numbers, and just push the "regular" button. 85 vs 87 octane regular gas has been argued for years here in Colorado.

I did find this in the jeep manual."Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty."

 

Higher Octane does not mean Higher Quality. Premium gas does not mean a Higher Quality then Regular Gas either. It simply means it has a higher Octane. Higher Octane fuel is necessary in some engines with a Higher Compression Ratio. Engines with a Higher Compression Ratio can be susceptible to preignition or “knocking”. Buy/Use the lowest octane fuel that that your vehicle will burn without “knocking”. If you notice knocking on a tank of 87 Octane, fill up with 89 next time. Do not feel like you’re not giving your baby the highest quality food that it deserves. Of course the gas station wants you to believe this, otherwise they wouldn’t market the higher priced, higher Octane fuel as “Premium”. My Hemi required 89. My new WK2 does great on 87. As mentioned earlier, if it’s quality gas you are concerned about (and you should be), buy from national branded station that is BUSY. They’re most likely to have the freshest gas in their tanks.

 

Buy/Use the lowest octane fuel that that your vehicle will burn without "knocking". If you notice knocking on a tank of 87 Octane, fill up with 89 next time.

If you notice knocking these days, there is something way wrong with the engine. The computers are sophisticated at detecting the conditions leading up to preignition (ping/knock) and adjust timing (reducing power) to avoid it. The so called knock sensors pick up the ping at a level no ear can hear. So you wouldn't know whether 87 or 89 is better by ear. Seat of the pants feel, mpg, or a dyno perhaps, but you can no longer optimum tune by ear .

In the US, there are additional cleaners and conditioners in premium fuel. It may be useful to fill the tank with premium a couple times a year to clean thinks out.

Otherwise use the fuel you want, but you should follow the manufactures suggestion.

 

The engine calibration will have a base spark advance map (based on engine speed, load and other inputs such as EGR rate) which will be completed using the recommended fuel octane. Usually, the engine control will not increase the spark advance beyond the base map, just reduce if pre-ignition is detected. So there is no point in running a higher fuel octane than recommended since the controller will not optimize the spark advance for this fuel unless you happen to have an engine where the stack-up of tolerances would lead to pre-ignition with the recommended fuel. I would expect this to be a very small population of vehicles.

 

Here's the Take-Away from all of this...
Lower than recommended Octane: Bad on your engine, your fuel efficiency and your warranty.
Manufacturer Recommended Octane: Perfect
Higher than recommended Octane: Unnecessarily Bad on your wallet.

The following is copied directly out of my 2016 Jeep Grand Cherokee Overland Owner's Manual:

FUEL REQUIREMENTS (STARTING AND OPERATING p.575)
3.6L Engine
Do not use E-85 flex fuel or ethanol blends greater than 15% in this engine.
These engines are designed to meet all emissions regulations and provide optimum fuel economy and performance when using high quality unleaded "Regular" gasoline having a posted octane number of 87 as specified by the (R+M)/2 method. The use of higher octane "Premium" gasoline is not required, as it will not provide any benefit over "Regular" gasoline in these engines.
While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see your dealer imme- diately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty.
Poor quality gasoline can cause problems such as hard starting, stalling, and hesitations. If you experience these symptoms, try another brand of gasoline before consid- ering service for the vehicle.