What are you scanning for exactly?
Using a lower octane fuel than recommended
- Thread starter The Critic
- Start date
I’m not doubting you, so if this comes off that way I apologize, I’m actually genuinely curious. And I’m throwing out all the economics of whether or not it’s worth it here.
Isn’t knock retard just a small part of an overall bigger picture? I remember when I had a Diablo tuner there was base spark, short term knock, and long term knock. Like say you’re running 87 in a car that “recommends” 91, it’ll run at (made up numbers) a base spark of 20°, whereas on 91 it’ll run 35°. You may get a few more short term knock events, but overall you’re still making a bit more power and getting a bit more fuel economy vs running 87, or am I completely wrong in my thinking?
We can see the current octane being used, and how many tanks of each octane level since new.
You can record KR or the voltage of the sensors on my VWs. I also typically record total timing advance. Let's use my Golf b/c I log it all the time. Total advance is 15 deg max. Any KR will knock that back (no pun intended!) a bit so at most when I'm running sub-par fuel/no E I may be getting 12 deg total advance for example. The "Base" as you say is now 12 as the ECU collects short term/long term data during the drive and reduces trying to push up to 15 b/c it can't without getting KR events. Is that what you are talking about? You are for sure leaving power on the table when you can't get the full advance. I know for my Golf, I'd rather see some minor KR and push the advance vs. back off the advance to see zero b/c I can gauartee I'm making more power with a few ticks of KR once in a while but pushing it.
On what vehicle? So these have a fuel sensor that measures octane?
No, if you are talking saving cost, rather than use lower than recommended octane, it is better cover 1/3rd area of your air filter with cloth, this will give you same impact but much safer.
The ecomomics of this discussion are a bit off to me based on how many people/internet lore has it - that running premium nets enough mpgs/fuel economy improvemet to justify itself. Let's use my son's Lexus, meant to run 91, that we run 87 in. I have not done a detailed study (using Fuely for example) so my numbers are more seat-of-the-pants/based on haivng this vehicle for the last year and a half and noting fill up mileage/volumes. We didn't note any difference in the mpgs going between 93 and 87 but for the sake of this discussion, I've shown a ~13% increase which to me is huge and likely way too much - it's likely 1 mpg or so. To break even, you would need a ~30% increase in fuel economy which is not happening and to make it worthwhile, you'd have to be above 30%. This obiously assumes your vehicle can safely run lower octane gas and that it will have acceptable performance etc. For us, it's been a no-brainer based on driving it.
Hermann
Site Donor 2023
In my world, there seems to be 87 octane fuel on which my Venza runs better. Last Sunday went country road driving. The fuel in my tank was from the local grocery chain. Was running low and bought 5 gallons at a BP station. Within a mile or so the engine perked up and was more responsive to the throttle and just seemed happier. I checked to make sure the car was still in the Eco drive mode. It was. Tempted to try 89 octane but the prices around here for premium grades is stupid right now.
Filled up last night at a Phillips 66 station. The MPG was 40.8 for the tank with two different fuel brands. About 80% of the tank was at higher speeds in VERY windy conditions. After 4 tanks the Venza is averaging 41.6 MPG. I'm happy.
Filled up last night at a Phillips 66 station. The MPG was 40.8 for the tank with two different fuel brands. About 80% of the tank was at higher speeds in VERY windy conditions. After 4 tanks the Venza is averaging 41.6 MPG. I'm happy.
On BMW. No, there is no octane sensor.
Then how is it telling you what gas is in it?
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I have an 04 infiniti FX45 with 190000 miles on the clock. It requires 91 octane, however, I live at elevation above 4000ft so I recently tried a full tank of 87 octane. I had no audible knock or any loss of power I could feel. What was weird is that I got about two more MPG on that tank - measurably better fuel economy. What I suspect is that the 91 octane, nowadays, has more detergents and may be using more ethanol to get the higher octane and, therefore, has less energy per given volume than the 87 octane.
That said, if I were at sea level, I would not attempt to run a lower octane than what the engine requires.
That said, if I were at sea level, I would not attempt to run a lower octane than what the engine requires.
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I also have a 04 Toyota 4runner V6 which requires 87 octane and I have experimented using 91 octane which turned out to produce noticably better power and smoother idle even here, in Reno NV, at elevation above 4000ft.
So... Each engine is different.
So... Each engine is different.
OVERKILL
$100 Site Donor 2021
Interestingly, around here (with the exception of Petro Canada Ultra94) at some Esso, Shell and Canadian Tire stations, it's the 91 octane that proclaims/has proclaimed to have no ethanol, while the 87 indicates up to 10%:
Canadian Tire:
Shell:
OVERKILL
$100 Site Donor 2021
Better for OPE and boats that sit, I know that's why it's desirable up here.
Zee09
$200 Site Donor 2023
I keep hearing that around here but haven't seen it. I would be a buyer.
Overkill it is time for beddie...
Zee09
$200 Site Donor 2023
And mowers here..
OVERKILL
$100 Site Donor 2021
Mowers is covered under "OPE"
Zee09
$200 Site Donor 2023
Yip how about OBP?Mowers is covered under "OPE"
I was talking specifically about my own mowers..ethanol has made my life miserable
Ah, so for boats....I also have heard for lawn mowers etc.
