Quite an interesting way to test this. I like how he adjusted the advance. Of course like all his testing translating to a modern ECU-driven vehicle with knock sensors, turbos, and DI will impact it but I'd say this paints the picture with some accuracy.
Project Farm testing impacts of octane and ethanol content on power and mpgs...interesting!
- Thread starter TiGeo
- Start date
It will be interesting to see how this thread goes. BITOG folks love to hate on PF. I mean, I kinda get why, but, when taken in the correct context, I find most of his videos interesting. The guy puts a lot of time, effort, and creativity into what he does. Are they the absolute end all, be all definitive authority on everything? Of course not, but I don't think that he claims them to be either.
A number of car magazines have tested this over the years. One was with a Porsche 911. The premium fuel even with the price gap was worth the extra money due to performance loss on the cheap stuff.
when shell super first became 10% eath i consistently lost 10 MPG calculated on the carbd 08 1200 cc porkster i had + even among various 10% eath premium my chipped 2001 turbo jetta ran rougher on some brands + when i could find it shell premium ran BEST! PF has "some" interesting vids BUT remember these are lo tech low dollar comparisons!!
Kestas
Staff member
If acceleration is important to you, stick with premium fuel. Otherwise, regular will give you the best economy for going from point A to point B. From my records, I get no perceptible loss in gas mileage by using regular fuel where premium is recommended. All my cars have knock sensors.
Top Tier (?) 89 w/10 is used most of the time for both cars . FIT is E.F.I. and other is the G.D.I. of the Accent . Last fill for FIT ( E.F.I.) was T.T. (?) 93 w/E10 . At one time could get Top Tier 89 w/E5 . 90 non E that's not Top Tier is always used for small engines .
Last edited:
Please correct me if I'm wrong.
Higher octane gas burns at slower rate, thus some engines not meant to run it may show higher cat 'poisoning' rate due to incomplete burn and/or exhaust valve burn due to 'still burning' fuel mixture going past exhaust valves?
Higher octane gas burns at slower rate, thus some engines not meant to run it may show higher cat 'poisoning' rate due to incomplete burn and/or exhaust valve burn due to 'still burning' fuel mixture going past exhaust valves?
I doubt it. A slower flame front is a better way to look at it. Ever wonder why some exhaust headers glow orange?
I got a tune, got rid of the cat and burn 93 oct in a 91 oct tune. Gas mileage went up around 5 mpg. Car is 87 oct limpable if needed.
My '08 Accent at 110k miles or so the cat went out. No missfire history or other problems.
I enjoyed the video.
If life has taught me anything about gas these past too many years, the brand of gas seems more important than the octane.
If life has taught me anything about gas these past too many years, the brand of gas seems more important than the octane.
No, in and of itself the octane rating does not affect the burn speed. In fact it doesn’t affect anything (including the energy content) except for the resistance to pre-ignition.
Having said that however there are multiple ways to influence the octane rating other than varying the branching of the octane molecule.
dnewton3
Staff member
Octane is a compound which primarily resists predetonation. It does nothing to "add" energy.
However, higher octane values allow for higher compression ratios to be used, and also to advance spark somewhat, both of which can have the result of increasing power and efficiency. What octane does is allow for other parameters to be optimized, which result in beneficial effects, if and only if the system can be adjusted for those benefits.
My MX-5, for example, is GDI and has variable electronic spark mapping curves. It can use the knock sensors to check for pre-ignition events when "adjusting" the timing (spark advance). I get about 2 more mpg using 91 octane gas over 87 octane gas. It's not cost effective; the 91 fuel costs about 30% more for perhaps 5% more mpgs; the ROI doesn't pay out. But I still run the 91 to maximize the available distance per tank.
The gas Honda engines PF used in his video clearly don't adjust timing automatically. So there's no benefit to running anything above what is safe to run without predetonation.
However, higher octane values allow for higher compression ratios to be used, and also to advance spark somewhat, both of which can have the result of increasing power and efficiency. What octane does is allow for other parameters to be optimized, which result in beneficial effects, if and only if the system can be adjusted for those benefits.
My MX-5, for example, is GDI and has variable electronic spark mapping curves. It can use the knock sensors to check for pre-ignition events when "adjusting" the timing (spark advance). I get about 2 more mpg using 91 octane gas over 87 octane gas. It's not cost effective; the 91 fuel costs about 30% more for perhaps 5% more mpgs; the ROI doesn't pay out. But I still run the 91 to maximize the available distance per tank.
The gas Honda engines PF used in his video clearly don't adjust timing automatically. So there's no benefit to running anything above what is safe to run without predetonation.
Last edited:
You're wrong. Octane only refers to the auto-ignition point of the end gases, nothing else. It has no effect on burn rate, flame speed, efficiency, etc...
dnewton3
Staff member
Again, PF is for entertainment. Nothing he does is true "science" and would be scoffed at and summarily dismissed in a professional testing environment.
The variability in his testing is laughable.
The variability in his testing is laughable.
Last edited:
I'll bet that 99.9999% of the drivers on the road, couldn't tell which octane of gas was put in their vehicles, if someone else filled it up, and didn't tell them.
My most driven car is a Honda Accord.
I use regular in it...but lets say that I lent it to someone, and it got really low on gas, so they stopped and filled it up with premium, then returned it to me.
Unless they told me, I would never know that they used premium instead of regular.
In fact on this very car when it was about a year old, and had always been burning regularly gas, someone told me to use premium gas and reap the better mpg, running smoother, and performance gains. So I tried 3 tank fulls of premium in a row in my Accord. There was absolutely no perceptible difference in how it ran, performed, or mpg.
I went back to regular, and no change.
About 5 years ago while on a vacation trip in it with my wife, she filled up with premium at a gas station, i was inside taking a wizz.
That night she told me that she put in premium, and that is the only reason I knew. Had she not said anything, I would have never known. I told her to buy the cheap stuff, it doesn't make any difference so why use premium.
My most driven car is a Honda Accord.
I use regular in it...but lets say that I lent it to someone, and it got really low on gas, so they stopped and filled it up with premium, then returned it to me.
Unless they told me, I would never know that they used premium instead of regular.
In fact on this very car when it was about a year old, and had always been burning regularly gas, someone told me to use premium gas and reap the better mpg, running smoother, and performance gains. So I tried 3 tank fulls of premium in a row in my Accord. There was absolutely no perceptible difference in how it ran, performed, or mpg.
I went back to regular, and no change.
About 5 years ago while on a vacation trip in it with my wife, she filled up with premium at a gas station, i was inside taking a wizz.
That night she told me that she put in premium, and that is the only reason I knew. Had she not said anything, I would have never known. I told her to buy the cheap stuff, it doesn't make any difference so why use premium.
Wow! Can you say Adderall ?
Definitely a drivability difference between regular and premium in a VW turbo especially if it’s specd for premium. All my turbos get premium whether specd or not.
I also buy premium for the high detergent levels. The others need Techron once in awhile.
I also buy premium for the high detergent levels. The others need Techron once in awhile.
Some engines with appropriate sensors will respond better to higher octane fuel. That's a feature of the engine and not the fuel itself.
Higher octane has nothing to do with speed at which things burn, it's how much it resists ignition....once it's burning it's burning!
Last edited:
Here is my Atlas with a 3.6L VR6 which used to call for premium/91+ in cars years ago now running off 87. Ignition correction/"knock retard" 87 vs. 93 shown on my graphs - logged using a VW scan tool on the same stretch of road/temps/conditions are "close enough" for BITOG. 93 for sure is reducing the timing corrections under WOT which will translate to more power but interesting that it still gets some...a few gallons of E85 would zero that out most likely. This is in winter so winter blends which quite honestly suck and cause more KR than summer blends based on lots of logging on several vehicles I own. Not worth the cost for my wife to bee-bop around in but if I was towing or in the mountains, I'd run 93 based on these data. Feels the same to me but clearly logging indicates I'm getting a bit more out of the 93. Just say yes to data and no to butt-dynos!
Well, apparently I have a gap in understanding things.
Now, can I get a good explanation why some engines require high octane gas? Is it to do with compression, piston travel, RPMs?
Now, can I get a good explanation why some engines require high octane gas? Is it to do with compression, piston travel, RPMs?
Similar threads
- Locked
- Locked
