I know, I stopped doing it,beyond some peoples comprehension.
I wonder if the flat landers that move or visit here wonder why all the pumps show 2 points less?
Cheap alternative to premium?
- Thread starter AJB0009
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I wonder if the flat landers that move or visit here wonder why all the pumps show 2 points less?
But it's not universal. I certainly wouldn't use it for any number of reasons, including that I haven't driven a car where the owner's manual said it's OK in over 30 years. I remember my dad's 1982 Oldsmobile had a message in the owner's manual that 84 was OK. Then there's forced induction which helps boost the amount of air. If I was passing through I certainly wouldn't use it since I'd probably need to be back at lower elevation in short order.
Still - there are any number of different things that might be done to compensate besides just turbos being able to reach the same maximum boost as at sea level. An ECU might be able to advance timing at higher altitude because of less chance of detonation.
I give up.
There isn't a single manufacturer who recommends it any more for newer vehicles. Or the feds. I don't know why they still sell it, but it's a bad idea.
What is 85 octane, and is it safe to use in my vehicle?
The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower—because it was cheaper and because most carbureted engines tolerated it fairly well. This is not true for modern gasoline engines. So, unless you have an older vehicle with a carbureted engine, you should use the manufacturer-recommended fuel for your vehicle, even where 85 octane fuel is available.
Most modern vehicles with fuel injection can automatically compensate for higher altitude. The Electronic Control Module (ECM) (also called Electronic Control Unit ‐ ECU) will adjust the fuel mixture for higher altitude to prevent the engine from “running rich” (too much fuel in the mixture, and not enough oxygen). This can be accomplished with both liquid and gaseous fuels through the use of an oxygen sensor, which ensures that a constant fuel/air ratio is maintained with altitude. However, above a certain altitude, the vehicle’s performance will suffer even with automatic adjustments in fuel mixture. Due to lower air density at high altitudes, the horsepower of an internal combustion engine will decrease approximately 3.5% for each increase of 1,000 feet in altitude (see Table 1).
I actually did this on my 19 F150 with a 5 liter. I have a dedicated 93 octane tune using HP tuners but I thought I’d be cheap and flash the stock tune back in and run 87 for the whole road trip.
I started data logging with my laptop to see if it would ping. Watching the knock retard, it was fine under normal driving, but as soon as you floored it, the KR would go to +5 and as high as +8 sometimes before the knock sensors would kick in and pull the timing back. Definitely not something you want to see regularly in a 12:1 compression engine. The truck was very sluggish, even for the stock tune.
I promptly filled it back up with 93 at 1/4 tank which netted about 91 octane. Ran the same test again and no positive knock and the truck was adding timing from the time it was floored all the way to redline.
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Yep, my owners manual very specifically says “Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty.”
Would it “probably” be fine? Most likely. Will I risk a $5,000+ long block over it? Absolutely not, even if I did 100% of my driving at high elevation.
I'm surprised no one mentioned mixing 93 with 87 to get a 91 mix. Usually premium only calls for 91. A 1/3 mix of 87 plus 2/3 mix of 93 give you a 91 mix.
6.7 gallons of 93 at my current local gas prices would be $30.08 and 3.3 gallons of 87 is $13.17, $42.25 for 10 gallons. 10 gallons of straight 93 is $44.90, $2.65 savings isn’t worth the effort of doing 2 separate transactions IMO. Even at 20 gallons I’d simply give up buying a pop from the vending machine at work if that little bit mattered to me.
Turbos modulate boost via wastegates and blow off valves. I wouldn't be surprised that they can change the parameters in the fly.The piece I linked from Garrett is really about a specialty application where they're dealing with really thin air. I guess in that application, the ECU is linked to an altimeter to increase the boost at higher altitudes to make up for the reduced air.
I was under the impression that most turbos are physically capable of considerably higher boost than their typical settings, and that the boost is limited because they might damage the engine with too much. But at higher and higher altitude, that would only be compensating. They have a chart that shows how the boost is adjusted at sea level vs 10,000 ft to roughly produce the same power.
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With the GetUpside app I am getting 93 octane for the price of 87.
That said it isn't about the money as much as the entertainment value.
Isn't wastegate operation based on mechanical pressure differential? Not atmospheric pressure of course. But I was under the impression that turbos could bring it up to same internal pressures at altitude compared to sea level - at least up to a limit.
Yes.
Well, this certainly went in serval different directions than what I was anticipating.
Here is what I was originally thinking (hypothetical example):
15 gallons at $4 for regular: $60
15 gallons at $4.75 for premium: $71.25
Difference: $11.25
So, I thought if a person could fill up with regular and buy a bottle of octane boost for $6, there would be a savings.
That's all, simple.
~
A person or two mentioned about additives in octane boost that are harmful. Any elaboration about that? I don't know anything about it.
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I am no expert, but I thought too that if you use 87 and the engine is "lugging" some (up a hill, low RPM, high gear) that today's higher compression engines would start to ping. That is then detected by the knock sensor, which then retards the timing; somewhat reducing power. Correct?
I have switched back to 87, due to prices and my budget. It is noticeable in my Tacoma. When I drive some of the same hills that I always do, even slight grades, it will downshift to 3rd. On those same grades with 93 in the tank, it will stay in 4th gear.
In my Explorer, I have run 87 and 93, I have never noticed any difference in that whatsoever; shifting, power, or mileage.
Like someone mentioned, it likely depends on the vehicle, load, etc. My Tacoma is an extended cab too, so even a touch heavier.
Here is what I was originally thinking (hypothetical example):
15 gallons at $4 for regular: $60
15 gallons at $4.75 for premium: $71.25
Difference: $11.25
So, I thought if a person could fill up with regular and buy a bottle of octane boost for $6, there would be a savings.
That's all, simple.
~
A person or two mentioned about additives in octane boost that are harmful. Any elaboration about that? I don't know anything about it.
~
I am no expert, but I thought too that if you use 87 and the engine is "lugging" some (up a hill, low RPM, high gear) that today's higher compression engines would start to ping. That is then detected by the knock sensor, which then retards the timing; somewhat reducing power. Correct?
I have switched back to 87, due to prices and my budget. It is noticeable in my Tacoma. When I drive some of the same hills that I always do, even slight grades, it will downshift to 3rd. On those same grades with 93 in the tank, it will stay in 4th gear.
In my Explorer, I have run 87 and 93, I have never noticed any difference in that whatsoever; shifting, power, or mileage.
Like someone mentioned, it likely depends on the vehicle, load, etc. My Tacoma is an extended cab too, so even a touch heavier.
I probably missed it somewhere, but one bottle takes you all the way from 87 to 93?
That's a good question too. Like I said, I don't know anything about octane boosters.
Well all I know is that you have to be careful reading the labels, we once had a discussion on here and I learned that when it says it raises the octane rating by a number of "points" per ounce, that is 1/10th of an octane number. In order to raise it from 87 to 88 it must go up 10 points per the mixing instructions.
Depends on what it is. Tetraethyl lead is bad in many ways. Mostly it will foul your catalytic converters. Legally it can only be sold as additive for "off road" uses like racing or boating. Then there's MMT.
https://www.epa.gov/gasoline-standards/epa-comments-gasoline-additive-mmt
The potential negative health effects notwithstanding, MMT also tends to foul spark plugs and catalytic converters.
Really though. If there were some magic way to increase the octane rating of fuel in any way that was safe, cheap, and effective, it would have been jumped on by fuel marketers. I remember way back when Unocal had some special process for making cheap higher octane fuel, and they were selling 89 octane at a lower price at similar prices as other name brands' regular.
High mile engines often have deposits inside the combustion chamber that serve as catalysts or hot spots for pre-detonation so I respectfully agree with all the gents here who claim he gets nobennies from premium.
My Pathfinder has premium recommended but since it has 175,xxx miles on it I stick with premium.
However when I drive on high altitude interstates I drop down to midrange.
Which is 90 rather than the posted 89 Octane a lot of the time/
My Recommendation to the OP is to try mid range.
Octane boosters are more expensive than gassing up premium.
My Pathfinder has premium recommended but since it has 175,xxx miles on it I stick with premium.
However when I drive on high altitude interstates I drop down to midrange.
Which is 90 rather than the posted 89 Octane a lot of the time/
My Recommendation to the OP is to try mid range.
Octane boosters are more expensive than gassing up premium.
No, no, no...If you go up a hill, then down a hill and return to the exact same elevation you started from, you get back EXACTLY the same amount of energy going down as was needed to go up. Now put efficiencies into that equation, and it looks a lot different.
There's a lot of inefficiency in going downhill. Especially since most people end up using their brakes.
I think for most cars if you dropped down 800 vertical feet with 100% efficiency and no losses, it would be going well over 100 MPH. You have to hit the brakes somewhere or convert the energy to heat/noise.
