Octane experiments

higher octane can help if theres proper tuning, especially with turbos!! go to GoAPR a VW Audi etc tuner i have in my 2001 TT 1.8T stock 225 hp 91 oct 257 93 oct 263 with everything stock otherwise!! thats a proper complete tune $500 + just the tip of the iceburg as GEO knows + DI engines allow a LOT more if your driveline + WALLET are up to it. i had their switch chip in my 2001 jetta 1.8 T that changed tuning on the turn sig stalk + you surely noticed a stock 89 oct factory to 93 oct APR tune difference!!
 
No, I specified "on same gasoline".
There really isn’t such a thing. I linked an article here once that showed that the energy density of gasoline varies about 4% even at the same gas station. It’s why some of these incredibly detailed mileage statements are so silly and don’t take this into account. If you really want to measure fuel economy you have to at the minimum use standardized test fuel.
 
There really isn’t such a thing. I linked an article here once that showed that the energy density of gasoline varies about 4% even at the same gas station. It’s why some of these incredibly detailed mileage statements are so silly and don’t take this into account. If you really want to measure fuel economy you have to at the minimum use standardized test fuel.
I reiterate: same gasoline. Not a one-off measurement. I have 7 years of driving this car on this route in different temperatures using gasoline from the same station locally and for the long 500 mile day.

A cold week returns 26 MPG. The next week above 50°F it gets 32 MPG.
 
A modern engine is a variable compression air pump. It will tune to what ever octane you use. Minimum being 87 r/m. Engines adjust up to about 103 Ron fuels with out being tuned.

It's been 10 years or more since this tech and nobody understands it. I have had multiple Honda vehicles and all loved higher octane with out tuning including cars that don't require premium. My mpg goes up in summer and using premium gas even in winter is higher than mfg mpg rating for every car I used it in.

I am against tuning like you can't change what the ecu and PCM can already changes too based on sensor inputs. So basically a tuned vehicle is out of tune 90 percent of the time. I prefer to tune with fuel. Regular gas is basically the same but the premium gas is different from brand to brand.

Using premium will raise the useable compression which raises the efficiency and torque. Easily learned by reading engineering papers. There is 3 systems on a standard engine and the basic is in the ecu. The pcm controls all the systems. It has octane and knock control and power to the wheels as traction control.

I could talk about this and have in the past but everyone has there own opinions which is fine but if someone puts out an opinion and you disagree just saying no is not and opinion especially if there is papers out there. I won't share them because they are easily found.
 
A modern engine is a variable compression air pump. It will tune to what ever octane you use. Minimum being 87 r/m. Engines adjust up to about 103 Ron fuels with out being tuned.

It's been 10 years or more since this tech and nobody understands it. I have had multiple Honda vehicles and all loved higher octane with out tuning including cars that don't require premium. My mpg goes up in summer and using premium gas even in winter is higher than mfg mpg rating for every car I used it in.

I am against tuning like you can't change what the ecu and PCM can already changes too based on sensor inputs. So basically a tuned vehicle is out of tune 90 percent of the time. I prefer to tune with fuel. Regular gas is basically the same but the premium gas is different from brand to brand.

Using premium will raise the useable compression which raises the efficiency and torque. Easily learned by reading engineering papers. There is 3 systems on a standard engine and the basic is in the ecu. The pcm controls all the systems. It has octane and knock control and power to the wheels as traction control.

I could talk about this and have in the past but everyone has there own opinions which is fine but if someone puts out an opinion and you disagree just saying no is not and opinion especially if there is papers out there. I won't share them because they are easily found.
You can see that clearly in the logs I posted somewhere above in this thread, higher octane reduced knock which will result in a bit more power. It's ~5hp total and only at WOT. I got the 5hp increase from the same 3.6 VR6 rated 5hp higher than mine with the denotation *achieved with premium fuel from online VW-provided info. 5hp for nearly a $1 more per gallong and questionable mpg increases...just not worth it unless you are towing etc.
 
You can see that clearly in the logs I posted somewhere above in this thread, higher octane reduced knock which will result in a bit more power. It's ~5hp total and only at WOT. I got the 5hp increase from the same 3.6 VR6 rated 5hp higher than mine with the denotation *achieved with premium fuel from online VW-provided info. 5hp for nearly a $1 more per gallong and questionable mpg increases...just not worth it unless you are towing etc.
I did a quick look of that motor and it's not very efficient. I don't know how much regular you still had in the tank but 5 hp is a lot considering torque is closer to 8 pounds. It probably will go up as the ecu tunes itself. That motor if efficient should produce 330 HP. Remember I said your gains has to overcome VE. I will stop comparing to Honda but since Honda under rates HP and torque you can see what I mean.

Efficiency should offset the cost and there is more to premium than more power and mpg. Past cars gained 25 or more percent in mpg up until knock in my cars from the late 90s. Engines will be cleaner too.
 
did you measure that with a smoothometer?
Actually, "smoothometer" is the brand name of my butt dyno.

Seriously: There was a steep hill leading west out of Ticonderoga, NY. It's Rt 74 and climbs up Chilson Hill.
When we were young we'd advance the timing until we got a small predetonation zooming up the hill.
That made for a good tune for 99+% of our driving. And yes, fuel octane effected the results.
 
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I did a quick look of that motor and it's not very efficient. I don't know how much regular you still had in the tank but 5 hp is a lot considering torque is closer to 8 pounds. It probably will go up as the ecu tunes itself. That motor if efficient should produce 330 HP. Remember I said your gains has to overcome VE. I will stop comparing to Honda but since Honda under rates HP and torque you can see what I mean.

Efficiency should offset the cost and there is more to premium than more power and mpg. Past cars gained 25 or more percent in mpg up until knock in my cars from the late 90s. Engines will be cleaner too.
A bit of a disconnect here. These weren't my data, it was VWs. My data logs were after several tanks of each so "pure" 87 and 93. They list that motor in the owner's manual under the engine specs as 280hp* with the * achieved with premium fuel. It's rated at 275hp for the Atlas on 87. Engines won't be any cleaner on premium if using Top Tier 87. The fuel never touches the valves in DI. If a manufacturer could gain 25% mpgs running premium you bet you butt they would. Tuning the 3.6 to run on 93 would yield as you say, a bit north of 300 per APR/Unitronic other tuners that tuned it on other vehicles by advancing the timing to handle it. These engines don't have "hidden" tunes that are magically unlocked by running premium...needs to be adjusted in the ECU. Case-in-point...my Focus (son's now). NA 2.0 GDI. 87. Folks would say running premium gave more power which some evidence supported. But...we did a custom tune that took full advantage of 93. When he was at school he filled it with 87 because broke college student. Tells me "it's making a metallic rattle noise"...haha...it was audible knock when I drove it/loggged it/send logs to the tuner so clearly the stock ECU tune can advance the timing a bit to ride the knock sensors but nothing like a real tune for the premium fuel can do! The ways folks talk about this, you'd think that's what they are experiencing.
 
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Hyundai got caught saying all their vehicles got over 40 mpg years ago. Why because they went with premium during tests and got excited but it was lower with regular and people were upset. Under most driving conditions it is 25 percent higher but lower because of idling, short trips and heavy vehicles and weather conditions.

Biggest problem is people don't change driving styles. Lighter on the fuel pedal because of the torque increase. If I drive the limits with out passing on my commute I can get 50 plus mpg in my Civic sport. More than 25 percent. Without effort on the gas pedal.

VW and others are trying to make regular work. Octane was supposed to go to 91 r/m for regular this year but don't think that will happen. I would then use regular except when towing.
 
some cars have a power difference on premium, makes perfect sense to me. I've never seen this personally as i drive diesels, or old trucks with a 9.0:1 compression ratio.
 
I've always just put regular gas in my vehicles, never saw the need, never had one that called for higher grade. Some recent threads and my BIL talking about his results using premium while towing got me a little curious so decided now gas price has come back down I'd try different grades. The '02 Xterra is our DD so it made sense to use it and it's pretty gutless so maybe any difference would be noticeable. Premium where I get gas is 91 so I started with it. I can't say I noticed any difference in power, smoothness, starting, and the mpg for the tank was right in line with normal fill ups. I hand calculate every tank by habit. There was one thing that happened that indicated a difference. On a 4 lane bypass road that I drive 2-3 times a week every week and have hundreds of trips on it by now there's a 1 mile uphill grade, not steep, that every time @ 65 mph the Xterra will downshift around 3/4 of the way up. Every time. With the 91 gas it has not downshifted one time. I ran 2 tanks of 91 and it pulled the grade every time. I use cruise at 65 and it hasn't mattered time of day, temperature, wind direction. I then ran it low and filled up with 89 and saw the same results, nothing notable while driving but it pulled the grade over the top every time through 2 tanks and I'm into the 3rd tank now. Fuel mileage right in the range I'd see with 87.

My guess is the higher octane is holding timing and it's just enough to pull the grade. This to me is more than anecdotal, in 4 years of traveling this road in every condition the Xterra has always downshifted, now with both 89 & 91 it has not downshifted one time. Is this little thing enough to make me want to run 89 at 25 cents more per gallon? Likely not. On our next towing trip I'm going to run some tanks of 89 out of curiousity.
I noticed the same thing in our 2015 Odssey.
Especially on a hot summer day with it loaded up and the AC blasting.

91 has a purpose in vehicles reccomending 87.
 
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