Octane experiments

I used to get 50 mpg in my civic B4 my turbo. No one believed me. Cold temps is an automatic 25 percentage in mpg loss. Knock retard is the same as when you start a cold motor in winter until it warms. Now I get 37 to 38 average with no reguard to mpg. I enjoy passing everything but if I slow down to the speed limit I see 60 mpg on the iMID.

BP or Shell is what I normally use but on occasion I use Walmart gas which is Exxon without their additives but they use better additives in their premium according to a manager I've known for years.
 
I used to get 50 mpg in my civic B4 my turbo. No one believed me. Cold temps is an automatic 25 percentage in mpg loss. Knock retard is the same as when you start a cold motor in winter until it warms. Now I get 37 to 38 average with no reguard to mpg. I enjoy passing everything but if I slow down to the speed limit I see 60 mpg on the iMID.

BP or Shell is what I normally use but on occasion I use Walmart gas which is Exxon without their additives but they use better additives in their premium according to a manager I've known for years.

Are you running larger injectors? How does the iMid compare to hand calcs?
 
Are you running larger injectors? How does the iMid compare to hand calcs?
No stock. Stock injection is good to 350hp. More than the rods could handle. Imid is accurate for BP but others the mpg is a little lower.

There is no high cams just vtc which is basically variable compression. The ecu will tune up to 2200 kpa 1400 NA on premium gas. 1100 to 1200 on regular maybe higher under certain conditions. Air is controlled by the turbo and runners in the intake.
 
Your tuning company would be great.
You: "Custom tunes, adds 100hp, no logging needed!"
Potential customer: "Can you show me your dyno sheet or some logs?"
You: "No, I just need to Jedi-touch it or hear it and I'll be able to adjust the fuel/timing/boost. If you can't tell how much power was added or what adjustments it needs I guess you really shouldn't be in this game."
Customer: "Ok cool, I'll take it!"
Car blows up.

I don't have a tuning company or make outrageous claims.

The threadstarter avoids 1 single downshift on a hill with premium grade when compared to regular and all the forum members panties get in bunch.
 
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.
Now go back to 87 and verify that it will now shift on that grade again every time.
 
GM and a few other makers have stated they want a new high octane standard. They can build engines that get higher fuel economy along with lower emissions. The problem is that most are addicted to the cheapest gas at the pump.
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lpg -20% co2, 1/2 price. i don´t understand why people are avoiding gaseous fuels... its a waste byproduct of natural gas and crude.
to extract maximum, even higher than common 11:1 cr could be used. not a problem because :
A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air–fuel mixture due to its higher thermal efficiency.
ethanol is b$, making food expensive.
 
main-qimg-03d9bcdbed9dc9b20f4376a51556acac-lq

lpg -20% co2, 1/2 price. i don´t understand why people are avoiding gaseous fuels... its a waste byproduct of natural gas and crude.
to extract maximum, even higher than common 11:1 cr could be used. not a problem because :

ethanol is b$, making food expensive.
E is so good for knock resistance if you have a performance car.
 
Modern ECUs are so flexible they actually do get extra power out of premium over regualar. No retune needed.
just one example in recent years Nissan has made particular efforts to quantify this which is why , for example, they publish their Titan at 390 hp with regular and 400 hp with premium (which IMO is a conservative difference)

I recentl saw a report somewhere, maybe even on here, where they took several vehicles and dynoed 10-15 hp difference from regular to premium (this was mostly on smaller engines)
The point the report was trying to make that you can never feel a difference from that so premium "isnt worth it"
To that I beg to differ as many enthusiasts spend a couple gran for an exhaust system and breathing mods and in the end they gain maybe 15 ish hp, if that.
My XTerra which asks for regular, gets mid range, my Pathfinder which says premium recommended and regular ok, gets 93 octane.

I live at sea level + both engines are high miles (166,xxx and 185,xxx miles respectively) in one of the warmest states of the union so I also like that extra protection from summertime knock.
 
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 haven't read through the whole thread yet, but I have to report that I noticed exactly the same thing here with UK fuel. I went from 95 octane to 99 octane (which was 0% ethanol as well). On a route I did every day for 3 years I noticed that the car was much happier labouring at a lower rev level (Say 1600rpm) rather than often dropping down to the gear below and raising the revs to say 1800 or so.
 
Because in the context of the fuel octane rating it is a meaningless metric.
I'm happy for a metric that has hundreds of examples of same behavior with 87 and now dozens of examples with 89 and 91 with a different behavior that is indisputable and repeatable. It doesn't make any difference in the perceived daily performance of the Xterra but I did have a performance difference directly attributable to the different gas that's not a subjective feeling. From remarks here either it's holding timing or using the premium program in the ECU if it has that.

Now go back to 87 and verify that it will now shift on that grade again every time.
Going to.

What I got out of this is I'm going to try mid grade next time we're towing the travel trailer and see if there's a positive difference. Never too old to learn something.
 
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If you're going to tow a trailer use premium. At those loads you need to use the highest octane premium you can find. It will go beyond the knock control on regular.
 
For the last few months I have been running 91 octane E0 when it's available. It makes the hybrid perkier and faster, and 8-10% better MPG. The biggie is how it smooths it runs, very noticeable all the time and most obvious when the ICE first fires up.
That I know of, current Ford engines are the best at making use of higher AKI gasoline. Has never made significant difference in any other vehicle. Makes zero difference to my 2016 Yamaha FJR1300 or 2016 Subaru Outback 2.5i.

2018 Ford F-150 2.7EB likes 93 AKI, but not so much as the added cost.
 
I used to get 50 mpg in my civic B4 my turbo. No one believed me. Cold temps is an automatic 25 percentage in mpg loss.
We are supposed to believe only EVs suffer range loss in the cold. My Subaru Outback gets 26 MPG highway at 40°F and 32 MPG at 70°F on same gasoline, same 500 mile one day route.
 
We are supposed to believe only EVs suffer range loss in the cold. My Subaru Outback gets 26 MPG highway at 40°F and 32 MPG at 70°F on same gasoline, same 500 mile one day route.
Winter vs. summer blend fuel?
 
We are supposed to believe only EVs suffer range loss in the cold. My Subaru Outback gets 26 MPG highway at 40°F and 32 MPG at 70°F on same gasoline, same 500 mile one day route.

well, air density goes up when it's cold, so air resistance does too. This will impact ice more as they are generally less slick.
 
I wonder if in the future there will be one grade that might be a 90 Octane fuel. Makes sense to me. Ed
I hope not for those wanting higher octane/more power tunes.
 
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