So fuel quality does matter! or ARCO gas sucks, sort of...

[DevilDogDoc]

So I'll start by saying I have put ARCO fuel in all of my vehicles over the last 20 or so years, in all manner of cars from little Hondas, to Jeeps to BMW's and MBZ and have never had a fueling issue. Since they became Top Tier I felt even more justified in running cheaper fuel that in theory is the same quality.


So since I have had my Ecoboost, I have been running ARCO 91 exclusively and had not had any issues that I could see. In comes the Accessport which gives one the ability to see things that prior were unnoticed, like OAR and ignition retard. I'll explain: Since I got my Adam Tune, I have been carefully watching my parameters and noticed an issue. When cruising down the highway, 6th gear 75-80 MPH, on the slightest of inclines my timing would begin to be pulled back half a degree, a degree, sometimes two. When this would happen the OAR would begin to pull back also, from -1.00 all the way down to -.82 at times. to fight this I would find myself in fifth gear at 80 MPH just to keep the RPM up which would stop this from happening. I had an ignition stumble which I traced back to my new(less than 1000 miles) on them Denso plugs which I got from Tune + when I got my tune, fouling out. So out went those plugs, in went a set of NGK's (one step cooler than stick) and the stumble/misfire is gone. So yesterday I had been thinking of fuel issues and as I had a long trip ahead and needed gas anyway so I put in half a tank of Chevron 91.

Well lo and behold, the issue seems to really have been my fuel. With only a 50/50 mix more or less the OAR is staying solidly at -1.00.The timing pulls a little and advances as it should, but the OAR stays the same. My drive to work is around 90 miles round trip, my run down is mostly downhill and the run back is mostly uphill, albeit a slight grade for most of it. It was in this run back that I would notice my timing being pulled and my OAR dropping like a rock. Well on my run home today I was giving it incrementally more gas in top gear, more than I normally did on the same stretches of road which would make it plummet before, OAR stuck at -1.00, even though the timing did retard here and there, but far less than before.

I knew that OAR was reflective of fuel octane, but the way I was thinking about it it was the timing causing the OAR to drop, but I guess it really is the other way the OAR was causing the timing to pull back.

So I guess the lesson here is that not all 91 octane is the same, even among Top Tier fuels. Here in California, we are already hobbled by 91 so getting the best fuel really seems to make a difference. I'll be filling up with full Chevron 91 on Wednesday so I'll find out how it is, but even on my mix its already leaps and bounds better. On a side note, my mileage went up a good bit from a 24-25 average to 27 as of right now. The 50 cents a gallon in price difference is well worth it to me in both peace of mind against detonation and knowing I'm getting the best cleaning fuels available to me.
And if my mileage continues to stay where it is, well that's just icing on the cake. I'll update in the next few days as I see anymore changes.

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[TheLion]

So I'll start by saying I have put ARCO fuel in all of my vehicles over the last 20 or so years, in all manner of cars from little Hondas, to Jeeps to BMW's and MBZ and have never had a fueling issue. Since they became Top Tier I felt even more justified in running cheaper fuel that in theory is the same quality.


So since I have had my Ecoboost, I have been running ARCO 91 exclusively and had not had any issues that I could see. In comes the Accessport which gives one the ability to see things that prior were unnoticed, like OAR and ignition retard. I'll explain: Since I got my Adam Tune, I have been carefully watching my parameters and noticed an issue. When cruising down the highway, 6th gear 75-80 MPH, on the slightest of inclines my timing would begin to be pulled back half a degree, a degree, sometimes two. When this would happen the OAR would begin to pull back also, from -1.00 all the way down to -.82 at times. to fight this I would find myself in fifth gear at 80 MPH just to keep the RPM up which would stop this from happening. I had an ignition stumble which I traced back to my new(less than 1000 miles) on them Denso plugs which I got from Tune + when I got my tune, fouling out. So out went those plugs, in went a set of NGK's (one step cooler than stick) and the stumble/misfire is gone. So yesterday I had been thinking of fuel issues and as I had a long trip ahead and needed gas anyway so I put in half a tank of Chevron 91.

Well lo and behold, the issue seems to really have been my fuel. With only a 50/50 mix more or less the OAR is staying solidly at -1.00.The timing pulls a little and advances as it should, but the OAR stays the same. My drive to work is around 90 miles round trip, my run down is mostly downhill and the run back is mostly uphill, albeit a slight grade for most of it. It was in this run back that I would notice my timing being pulled and my OAR dropping like a rock. Well on my run home today I was giving it incrementally more gas in top gear, more than I normally did on the same stretches of road which would make it plummet before, OAR stuck at -1.00, even though the timing did retard here and there, but far less than before.

I knew that OAR was reflective of fuel octane, but the way I was thinking about it it was the timing causing the OAR to drop, but I guess it really is the other way the OAR was causing the timing to pull back.

So I guess the lesson here is that not all 91 octane is the same, even among Top Tier fuels. Here in California, we are already hobbled by 91 so getting the best fuel really seems to make a difference. I'll be filling up with full Chevron 91 on Wednesday so I'll find out how it is, but even on my mix its already leaps and bounds better. On a side note, my mileage went up a good bit from a 24-25 average to 27 as of right now. The 50 cents a gallon in price difference is well worth it to me in both peace of mind against detonation and knowing I'm getting the best cleaning fuels available to me.
And if my mileage continues to stay where it is, well that's just icing on the cake. I'll update in the next few days as I see anymore changes.

The plugs tell us quite a bit, I'd take a look at this from Brisk as a further confirmation of your findings:

https://www.briskracing.com/spark-plug-diagnosis

It also provides a great visual of what the different issues result in.

 

[DevilDogDoc]

The plugs tell us quite a bit, I'd take a look at this from Brisk as a further confirmation of your findings:

https://www.briskracing.com/spark-plug-diagnosis

It also provides a great visual of what the different issues result in.

I read that whole thread while searching for why my plugs crapped out so fast and also the brisk info. I didn't see any evidence of preignition that I could tell. I will be keeping an eye on my plugs here to see how things look moving forward.

 

[TheLion]

I read that whole thread while searching for why my plugs crapped out so fast and also the brisk info. I didn't see any evidence of preignition that I could tell. I will be keeping an eye on my plugs here to see how things look moving forward.

Evidence of pre-ignition is pretty easy to spot, usually it results in oil draining from the hole in your block. Your engine can only survive a few revolutions of pre-ignition.

Knock on the other hand is fairly common and some NA engines actually run continuously with very mild knock due to the incorrect plug application. IMild knock is not destructive to the engine if corrected within a reasonable time. Detonation is the same as knock, just a different word, but implies greater severity.

Heavy knock or detonation is typically audible. Mild knock may go completely undetected by human ear. Not trying to be smarty pants, just wanted to clarify what the terms mean as I was confused by them myself when I was digging deeper into plug related issues.

Order of severity:

1. Pre-ignition - results in almost immediate engine failure
2. Detonation - if severe, results in pitting on the piston heads and will over a short time lead to cracked lands / damaged rings, typically the primary cause of cracked spark plug insulators. Mild detonation, or the more common term knock, can also damage plug insulators, but typically is not harmful if also corrected.

Based on my bore scope of cylinder # 4 and Brisk's analysis of the failed RR14YS plug insulator, they believe I had mild knock. The RR14YS plugs showed a mild yellowish discoloration to the insulator, indicating over heating. The OE plugs were pure white and showed no discoloration. I have yet to check the RR14S plugs, but will do so soon to verify they are running optimally.

Remember there are two distinct parameters that affect detonation and also pre-ignition as it relates to the plug.

1. Depth - the deeper the plug sits in the chamber (projected tip), the more effectively advanced the ignition is. It also causes higher thermal energy absorption (aka runs hotter). A projected tip plug runs about a 1/2 a heat range hotter than a non-projected variant. So while depth primarily affects timing, it does influence heat range as well.

2. Heat Range - insulator design and electrode material are the primary mechanism which affect heat range. Too hot and you increase plug wear, increase risk for knock and pre-ignition. Too cold and you have excessive fouling.

Brisk Plug applications are the following:

RR14YS for mildly modified or stock cars (stock PCM software).

RR14S for intermediately modified cars (tune, but with stock turbo and bolt ons).

RR12S for highly modified cars (tune, big turbo, nitrous, high boost).

 

[Weather Man]

Every Fall you get a rash of engine failures from guys who got their car tuned over the summer. Nice 3rd gear pull on a crisp Fall day, suspect fuel and BOOM! Good thing is that the latest engines do have much better timing retard with knock.

 

[TheLion]

Every Fall you get a rash of engine failures from guys who got their car tuned over the summer. Nice 3rd gear pull on a crisp Fall day, suspect fuel and BOOM! Good thing is that the latest engines do have much better timing retard with knock.

That was one of the basis for my arguments in using a more OE like software company such as the Ford Performance or Livernois. They test over temperature and various humidity conditions, under various loads etc.

Significantly lower ambient temperatures have a dramatic effect on timing and overall power output. Higher air density = more fuel to maintain optimal combustion = higher thermal waste as a byproduct.

I've had the hardest time conveying that when I defend my reasoning. To each his own though, not everyone lives in the same environment I do or has the same goals and / or risk / reward criteria I do either so it's circumstantial to a degree.

 

[ElAviator72]

Not surprised. I've heard nothing but disdain and mistrust for Arco gas in the 16 years I've lived in Arco territory...don't use it for anything other than fueling a rental car you're about to return or a rented moving van :lol:

Wow, can't imagine being held to 91 octane...it's bad enough that you can only get 92 up here in Oregon. Wish 93 pump was available like it is in most of the Southeastern USA.

 

[TheLion]

Not surprised. I've heard nothing but disdain and mistrust for Arco gas in the 16 years I've lived in Arco territory...don't use it for anything other than fueling a rental car you're about to return or a rented moving van :lol:

Wow, can't imagine being held to 91 octane...it's bad enough that you can only get 92 up here in Oregon. Wish 93 pump was available like it is in most of the Southeastern USA.

Well, I don't know that speedway 93 is much better, lol. My OAR is sitting around -0.61 from a small speedway station. Once I re-fill I'll try BP to see if the OAR changes. Car definitely seemed smoother on the BP gas, mostly at idle though.

 

[ElAviator72]

Every Fall you get a rash of engine failures from guys who got their car tuned over the summer. Nice 3rd gear pull on a crisp Fall day, suspect fuel and BOOM! Good thing is that the latest engines do have much better timing retard with knock.

Do you think the switchover from summer blended fuel to winter blended fuel (more VOC's, and gaseous components like Ethane and Butane which are missing form summer blend) has anything to do with this, too? That happens in the fall, too ;)

 

[TheLion]

Do you think the switchover from summer blended fuel to winter blended fuel (more VOC's, and gaseous components like Ethane and Butane which are missing form summer blend) has anything to do with this, too? That happens in the fall, too ;)

Hence why you need plenty of safety margin on a street car...fuel quality varies from station to station to a degree, there is a minimum standard, but additives and the condition of the under ground tanks as well as the volume of fuel (how long it sits) all affect what actually ends up in your car.

Without adequate engine management and testing through a wide range of conditions, your likely to run into problems at some point, especially in northern states where we get all 4 seasons in full swing (coldest days some times hitting -10~-20, hottest days hitting 95~100).

 

[Slow89]

Every Fall you get a rash of engine failures from guys who got their car tuned over the summer. Nice 3rd gear pull on a crisp Fall day, suspect fuel and BOOM! Good thing is that the latest engines do have much better timing retard with knock.

Exactly! Great post.... I don't know how many times I've seen the misconception that it's safer to run your summer tune during the winter. When In fact it's the other way around.

 

[Maggneto]

Well, I don't know that speedway 93 is much better, lol. My OAR is sitting around -0.61 from a small speedway station. Once I re-fill I'll try BP to see if the OAR changes. Car definitely seemed smoother on the BP gas, mostly at idle though.

Great discussions. My brother-in-law is a service manager at one of the busiest car dealerships in the Country for the past 20 years and he only uses BP gas. I personally only use BP or Exxon in all my vehicles (currently 2 GDI I4 Turbos, and a Jet Boat) and have never once noticed a knock or hesitation.

I would be very interested in your BP results.

 

[TheLion]

Exactly! Great post.... I don't know how many times I've seen the misconception that it's safer to run your summer tune during the winter. When In fact it's the other way around.

I can attest to this, with a recent fill up speedway gas (likely now a winter blend as we're at tail end of oct and temps are consistently in 30's to 50's), the LMS 93 tune just did not seem to like that tank of gas. No issues daily driving, but WOT and really pushing the car (5th gear pulls), it was very coarse and almost knocky (no I didn't hear any actual pining, but my intuition said NO to continuing to push the car).

Went back to 91 tune (still got half a tank) and the engine seems much smoother now. Honestly it's hard to tell the difference in power, mostly the 93 seems more edgy or sensitive.

https://itisscience.wordpress.com/2011/11/28/winter-gasoline-yes-there-is-a-difference/

I'd imagine this does affect combustion process and knock. Interestingly enough the cooler air, due to higher density, also means greater fuel to maintain optimal ratio, which results in higher chamber temps (brisk noted that fact when I was working out the cracked plug issue). Another factory which may increase risk of knock or detonation events. My opinion on the issue at this point isn't not worth the risk or trouble running the more edgy tunes in winter if you live in a true 4 season state (when combined with the already known variations in fuel quality from station to station).

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