Do we have to run premium?

[jmccorm]

marketing. It is true that higher octane gasoline have more additives, but here's the trick, they are petrol additives. And of course it does, it needs them to increase the octane! lol. In terms of detergent additives, it is the same for 87. You can buy high quality 87, as good as "premium" gas. Octane has absolutely nothing to do with quality.

Good answer, wrong topic... perhaps my fault. What are your thoughts on the affect of such added detergents (as you point out, regardless of octane) on engine life?

Sponsored

 

[entropy]

Good answer, wrong topic... perhaps my fault. What are your thoughts on the affect of such added detergents (as you point out, regardless of octane) on engine life?

I personally don't know. I've read that these detergents help reduce carbon deposits, thus help the long term reliability of the engine. The EPA has some requirements for these detergents, so they must do something. TOP TIER gasoline has been shown to burn cleaner and improve fuel efficiency.

But I don't know much about it, and I don't really pay much attention to it personally. We have really clean gasoline in avg in the U.S. because of EPA standards. Look at Los Angeles pollution levels 20 years ago vs. today. But at the pump, I really don't care and I don't buy into their marketing. I think our Jeeps will run just fine regardless of our choice in gas.

I am sure whoever is making these detergents is getting good business. So I like to keep an open mind on the subject.

 

[jeepoch]

great and informative post, I'm reading it a year later but wondering if you think the 2.0 has the potential (if well maintained) to reach that kind of mileage, or if the 3.6 is the better long-term option?

@randeeezy,

We have way more statistical evidence of the reliability and longevity of 3.6L but the 2.0L is still too new to predict it's long term behavior, at least not from direct statistical observation.

But my money is that they'll both be remarkable in the long term. I'll still side with the normally aspirated v6 as being the most reliable.

Jay

 

[F800]

I roll with 87. Mileage seems fine.

 

[Christian72]

Interessting to read, that many of you use patrol with 87 Octan.

For Germany the Jeep Wrangler user manual, that came with the car, points out that you have to use patrol not under 95 octan for the 2.0 T-GDi.

The engine is the same like in the states, I guess.

Here in Germany, some oil companies like SHELL offer even a high performance petrol (f.e. Shell V-Power Racing) with 100 octan or more, which I normally prefer.

Shell´s promise:

1. Keeps the engine clean
Shell V-Power has an increased number of cleaning molecules and innovative cleaning technology. It is our most effective fuel for keeping your engine clean and even removes deposits that have already formed.

2. Performance, power and acceleration
Shell V-Power Racing provides unsurpassed engine protection from performance-degrading deposits and achieves our best performance yet: up to 4% more power, up to 4% faster acceleration.

3. Less friction
Shell V-Power Racing forms a protective film on the cylinder wall, helping to reduce friction between the cylinder wall and the upper piston ring. The engine parts can thus rotate more freely.

Shell V-Power Racing's high 100 octane rating also improves knock resistance to support efficient combustion.

You may belive it or not, with my previous cars (Ford, Mercedes, Corvette) I could feel an improvement since I changed from 95 / 98 to 100 octan petrol.
If it is the same case for the Jeep, I can not say as I do not have a comparrion because I use 100 octan since the first day I own the car.

But I find it interessting that Jeep allows you to use 87 octan while in Germany they request to use 95 octan.

By the way, in Germany you do not get petol that is below 91 octan, but most of the cars request even 95 or 98 octan. Petrol with 87 octan is not offered

 

[JL MADDOG]

In cooler weather I usually run 87 and have no issues, even with a load or when climbing a grade.

In hotter weather, which is prevalent here in Arizona, I run 91. As the manual states, "The use of 91 or higher octane "premium" gasoline will allow these engines to operate to optimal performance. This increase in performance is most noticeable in hot weather or other heavier load conditions, such as while towing."

I have noticed a difference in off-roading with passengers & a load of recovery gear vs. running on pavement during the summer here.

 

[jjvincent]

Interessting to read, that many of you use patrol with 87 Octan.

For Germany the Jeep Wrangler user manual, that came with the car, points out that you have to use patrol not under 95 octan for the 2.0 T-GDi.

The engine is the same like in the states, I guess.

Here in Germany, some oil companies like SHELL offer even a high performance petrol (f.e. Shell V-Power Racing) with 100 octan or more, which I normally prefer.

Shell´s promise:

1. Keeps the engine clean
Shell V-Power has an increased number of cleaning molecules and innovative cleaning technology. It is our most effective fuel for keeping your engine clean and even removes deposits that have already formed.

2. Performance, power and acceleration
Shell V-Power Racing provides unsurpassed engine protection from performance-degrading deposits and achieves our best performance yet: up to 4% more power, up to 4% faster acceleration.

3. Less friction
Shell V-Power Racing forms a protective film on the cylinder wall, helping to reduce friction between the cylinder wall and the upper piston ring. The engine parts can thus rotate more freely.

Shell V-Power Racing's high 100 octane rating also improves knock resistance to support efficient combustion.

You may belive it or not, with my previous cars (Ford, Mercedes, Corvette) I could feel an improvement since I changed from 95 / 98 to 100 octan petrol.
If it is the same case for the Jeep, I can not say as I do not have a comparrion because I use 100 octan since the first day I own the car.

But I find it interessting that Jeep allows you to use 87 octan while in Germany they request to use 95 octan.

By the way, in Germany you do not get petol that is below 91 octan, but most of the cars request even 95 or 98 octan. Petrol with 87 octan is not offered

Just so you know, the Octane calculation in the EU is not the same as the US. Thus the EU numbers are higher. In addition to that, companies like Shell, pay to become the preferred fuel/lubricant for certain vehicles. Here's a reference:
"In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States."

https://www.economist.com/babbage/2012/09/17/difference-engine-who-needs-premium

I've been working on German cars since the 80's and this has been referenced numerous times in various Porsche and Audi service manuals. Thus, the sticker on the inside of the fuel door was just a universal one. Thus, people in the US have freaked out when their Porsche was required to use 98 octane, yet they could only get a maximum of 94.

 

[Christian72]

Just so you know, the Octane calculation in the EU is not the same as the US. Thus the EU numbers are higher. In addition to that, companies like Shell, pay to become the preferred fuel/lubricant for certain vehicles. Here's a reference:
"In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index). Thus, 97 octane “super unleaded” in Britain is roughly equivalent to 91 octane premium in the United States."

https://www.economist.com/babbage/2012/09/17/difference-engine-who-needs-premium

I've been working on German cars since the 80's and this has been referenced numerous times in various Porsche and Audi service manuals. Thus, the sticker on the inside of the fuel door was just a universal one. Thus, people in the US have freaked out when their Porsche was required to use 98 octane, yet they could only get a maximum of 94.

That explains it.
Learned something new again. Thank you.

 

[Maverick909]

I ran 87 the first few tanks on my 3.6 and after getting some bad knocking moved to just running 91 oct no matter what the extra 2-5 bucks a tank is worth it.

 

[4LOW]

In cooler weather I usually run 87 and have no issues, even with a load or when climbing a grade.

In hotter weather, which is prevalent here in Arizona, I run 91. As the manual states, "The use of 91 or higher octane "premium" gasoline will allow these engines to operate to optimal performance. This increase in performance is most noticeable in hot weather or other heavier load conditions, such as while towing."

I have noticed a difference in off-roading with passengers & a load of recovery gear vs. running on pavement during the summer here.

Same here. Running 87 in the 2.0 in the AZ summer has a negative effect on performance and mileage. The mileage hit is measurable (2+ mpg). The performance hit is an annoyingly sluggish response at light to medium throttle application.

 

[Grand Lake Special]

David,

I used to be a Powertrain Software Engineer for Chrysler back on the 2000 through 2008 model year programs. I helped design and implement quite a bit of the software on their Small Car, Large Car and Jeep/Truck Engine Control Module programs back then. And candidly, I had only left that really phenomenal gig in Auburn Hills, MI to move to the Front Range of Colorado. I still design and develop really cool software, just no longer for the automotive industry. However I feel I'm still qualified to answer your question.

As a matter of personal opinion (with some inside knowledge), I'm quite certain the owner's manual specifies using the lower octane (lower cost) fuel simply as a subtle mechanism to promote a lower cost of ownership for it's vehicles. If it did mention the possible range of fuels, or to use only the best possible fuel, may possibly turn some potential buyers off. Yet regardless of their reasons, they can certainly do a better job in trying to minimize the confusion on this subject. I suspect that their market research explicitly determined to avoid this subject altogether.

First, the car company needs to certify both emissions and fuel economy based on worst case fuel specifications, not the best. Second, there are indeed installed systems on the engine designed to detect knock dynamically (on-the-fly) in real time and adjust various engine parameters to decrease the amount of knock sensed. It does this through both dedicated knock sensors and engine performance metrics. The parameters adjusted are typically spark timing and fuel injector pulsewidth. There are other variables as well but this detail isn't really that important for our overall (informal) discussion. The physics and the implemented algorithms are indeed way more sophisticated than what I'm simply describing here.

However, while the engine can certainly 'react' to limit knock as it happens it is still nonetheless 'after-the-fact' of the knock event itself. In other words, the knock prevention algorithms only work after these conditions have happened to begin with.

The theoretical goal is to prevent any knock in the first place. Engine knock of any type or amount is DETRIMENTAL in some way. Knock is caused by improper detonation which works against the mechanics of the crankshaft's rotation. So rather than contributing to the engine's overall power output (torque) any knock at all, no matter how small, is retarding it. Unfortunately, this improper detonation can also cause piston damage (due to the unintended mechanical vibrations from the knock itself). These vibrations are acting on the piston and the rings causing excessive and undesireable wear on the piston's walls (all of it's sliding surfaces).

Suscinctly stated, the best possible internal combustion operation is therefore to NEVER have any knock whatsoever in the first place, period.

Another misconception is that octane is a measure of a fuel's energy content. This is false. Octane is a measure of the fuel's ignition flashpoint. The higher the octane value, the more consistent the pressure and temperature needs to be in order to ignite. It's a measure of the fuel's ability to combust at the exact same flash-point threshold reliably. The lower the octane, the larger the range of pressure and temperature values where this flash-point may occur.

Therefore the higher the octane, the more consistent this threshold is where the fuel actually ignites. The more consistent this is the easier it is for the engine controller software to determine and maintain the best possible spark timing, using the smallest possible injector pulsewidth (least amount of fuel) to produce the desired output torque based on accelerator pedal position (demanded speed).

Again with lower octane fuel, it's ignition flash-point is less consistent and the 'predicted' spark timing or pulsewidth calculation for each cylinder may not be as accurate for each particular combustion event. If this prediction is ever even slightly wrong, improper combustion can occur leading to a knock condition. So in theory, anything that can contribute to a more accurate combustion equation, where the spark is delivered to the piston's stroke in the most optimal position, lowers the probability for a knock event in the first place.

Recall, the engine controller software must always readjust it's variables to predict the spark timing for the next combustion event based on what it currently sensed for this as well as statistical calculations from some number of previous events. The more consistent these dynamics are, the smaller the adjustment required between events and the better the engine performs.

In summary, using premium fuel regardless of what they recommend and independent of whether you can afford it, will always be in both you and your engine's best interest.

I personally always use premium fuel and full synthetic oils (different topic). However, I achieved almost 300,000 miles on my previous vehicle, a 2005 Dodge Grand Caravan. The only thing that was not stock on it's 3.3L engine was a replaced water pump and an EGR valve. I might still be driving it if a distracted 16 year old on his phone hadn't pulled out into traffic. Luckily I swerved at 40mph, or he would have been T-boned. No one was injured but both vehicles were totaled. It's the reason I now have this wonderful JL Sport. I'm truly intending to put even more miles on this vehicle.

Hope this helps.
Jay

Nice job on the explanation++++++more people should read this>>>>>>>>>>>

 

[jeepoch]

great and informative post, I'm reading it a year later but wondering if you think the 2.0 has the potential (if well maintained) to reach that kind of mileage, or if the 3.6 is the better long-term option?

@randeeezy,
This is another question with very heated opinions. But from a physic's perspective, the more cylinders per rotation producing a subjectively similar amount of power output within an objective application (like Jeep level performance), the 3.6L V6 will need to produce less power per cylinder in order to achieve the same results.

Why do you think the four cylinder 2.0L Turbo and the V6 (naturally aspirated) 3.6L engines both produce near similar output power? Because there is a defined specification requirement to have a certain amount of minimum output power for a typical Jeep application.

The powertrain engineers then went forth with some power plant options to meet those requirements. They were providing the possibility in the Sale's Brochure the opportunity to satisfy the highest amount of potential market appeal to the largest number of potential buyers.

Both power plants have their pros and cons. Some drivers really enjoy the boost in acceleration when the turbo kicks in. Others enjoy power delivered more consistently at lower RPM's which is where most (perceived) Jeeping conditions occur. On trail is not necessarily the best place for a 0 to 60 speed trial.

Yet, Jeeps are sold to appeal to both the crawlers and the racers. This is not unintentional.

But to answer your question in a very constrained way, if (and this is a big if), the two engines are used in a similar way for strict comparison, the V6 should always deliver better reliable longevity simply due to the fact that with more pistons per crankshaft rotation there is less power needed per piston to achieve the same output. The six cylinder engines have a combustion event every 60° of crankshaft rotation compared to the four Banger's 90°. With less power required per cylinder event, there should be less wear and tear on all the engine's internal components.

This also assumes that maintenance and care, such as oil changes (as you point out) are performed properly on each power plant accordingly.

Before the flame war begins, there are many, (many) Jeepers who believe the 2.0L Turbo is the greatest thing since sliced bread. They will also berate and bemoan me for the fact I didn't mention that advanced modern engine technology accounts for this. Well to that too I say hogwash.

With more sophisticated components, such as the turbo, which has a lot more moving parts as compared to a naturally aspirated intake manifold, this only further increases the possibility of more things to fail. Simply stated: the larger the number of things that can go wrong will go wrong. This is a corollary on Murphy's Law which states: anything that 'can' happen, 'will' happen.

So from a completely conceptual high-level perspective, the 3.6L has a clear advantage in achieving a better statistical probability for greater long-term reliability. And additionally yielding a lower percentage of mean time between failures. Of course this is all conceptual until good scientific studies are performed to indicate the true reality.

I don't have, not do I plan on researching this further. But from anecdotal evidence based on market presence (overall time of either engine being produced), the 3.6L engine has a solid and very good reputation on this subject. The 2.0L is still rather new and has not enjoyed the same statistical scrutiny.

However, with all the disclaimers out of the way, every Jeeper will defend (rather religiously) the engine type they purchased. It's Human Nature to simply believe that your engine selection is the very best one ever manufactured.

Good luck at trying to convince anyone otherwise. Even though I just attempted to. Stupid, stupid me...

Best Regards,
Happy Jeeping (no matter your engine),
Merry Christmas to you and yours.
Jay

Sponsored