91 octane or 87, 2025 BS BL

[Jim Bow]

I suspect for my use, not really towing or anything I should probably stick with 87 and maybe every 5th tank fill it with 93 to clean it up a bit. I might be wrong, I'm still learning about this, so if there is no benefit using the 93 as far as helping keep crap out, then let me know, I'll save the 21 extra dollars

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[Escape2Bronco]

I suspect for my use, not really towing or anything I should probably stick with 87 and maybe every 5th tank fill it with 93 to clean it up a bit. I might be wrong, I'm still learning about this, so if there is no benefit using the 93 as far as helping keep crap out, then let me know, I'll save the 21 extra dollars

93 from the same gas station isn’t any cleaner than 87, it’s higher octane which prevents knocking in higher compression engines or engines tuned which require higher octane because of spark settings. For cleanliness, you want to use tier one or top tier gasoline which can be different between different gas stations.

 

[Jim Bow]

93 from the same gas station isn’t any cleaner than 87, it’s higher octane which prevents knocking in higher compression engines or engines tuned which require higher octane because of spark settings. For cleanliness, you want to use tier one or top tier gasoline which can be different between different gas stations.

Thanks for the explanation! The Mobil that I use is indeed Top Tier according to logos on their pumps.

 

[Stircrazy]

Yeah, I suspect thats where you would see a better gain all around. Short trips around town don’t make it worth it largely because of the repeated acceleration from a standstill—you’re constantly overcoming inertia to accelerate and you’re never doing a constant speed for any decent length of time. Succinctly all the stop-and-start driving.

I used a baseline of 3940 km. distance driven. I first figured getting 12.3L/100 km. at $1.26 per litre (87 octane). Then I figured getting 12.1L/100 km. at $1.42 per litre (91 octane). These were the current cheapest prices in my area yesterday. The result was the 91 octane cost $66.35 more over the 3940 km. distance. 3940 km. is the distance I’ve driven since I took delivery of my Bronco Sport on Oct. 11 last year. I project I’ll have about 4180 km. by Oct. 11 this year in about three weeks time.

In terms of cost the slightly better fuel economy isn’t worth it. However, your engine does run better so one might see that extra $66 as an investment in better performance and engine health.

the only difference between premium and regular is the octane level. all that does is resists predestination more, so what it allows you to do is run a little more timing and run at higher rpm with out predestination occurring hence it gets a little more power because of the added timing. the detergent levels and everything else is the same base, some companies may add different levels of the components to the base and ethanol level make a difference in the timing and power you can make and be carful also, some premium gas is ethanol free and yes there would be a big difference between using a 10% ethanol 87 octane and a 94 octane ethanol free gas, but when some one says premium I am talking 91 Octane which is getting very hard to find with out ethanol, and only certain places have the 94

I have driven 40000km to work and back this year so far I did 10000km with premium and 30000 with regular, for the premium I got 6.8l/100km and with the regular I get 6.8l/100 km that is pretty much all highway driving at 120kph, up hill one way and down hill on the way back (for the most part) when I put the off road tires on that number for regular changed from 6.8 to about 7.6L/100km..

how are you getting in the 12's.. I am only high 8's with all town driving..

 

[Escape2Bronco]

the only difference between premium and regular is the octane level. all that does is resists predestination more, so what it allows you to do is run a little more timing and run at higher rpm with out predestination occurring hence it gets a little more power because of the added timing. the detergent levels and everything else is the same base, some companies may add different levels of the components to the base and ethanol level make a difference in the timing and power you can make and be carful also, some premium gas is ethanol free and yes there would be a big difference between using a 10% ethanol 87 octane and a 94 octane ethanol free gas, but when some one says premium I am talking 91 Octane which is getting very hard to find with out ethanol, and only certain places have the 94

I have driven 40000km to work and back this year so far I did 10000km with premium and 30000 with regular, for the premium I got 6.8l/100km and with the regular I get 6.8l/100 km that is pretty much all highway driving at 120kph, up hill one way and down hill on the way back (for the most part) when I put the off road tires on that number for regular changed from 6.8 to about 7.6L/100km..

how are you getting in the 12's.. I am only high 8's with all town driving..

The few station in the Midwest near me only have ethanol free in 91. I run that in my mowers and motorcycle. I’d run ethanol free 87 if they had it. Also, people should take note if it’s a single hose pump with multiple grades. The first 1/4 gallon or so will be what ever the last person used.

 

[BLUEOVALRACER]

the only difference between premium and regular is the octane level. all that does is resists predestination more, so what it allows you to do is run a little more timing and run at higher rpm with out predestination occurring hence it gets a little more power because of the added timing. the detergent levels and everything else is the same base, some companies may add different levels of the components to the base and ethanol level make a difference in the timing and power you can make and be carful also, some premium gas is ethanol free and yes there would be a big difference between using a 10% ethanol 87 octane and a 94 octane ethanol free gas, but when some one says premium I am talking 91 Octane which is getting very hard to find with out ethanol, and only certain places have the 94

I have driven 40000km to work and back this year so far I did 10000km with premium and 30000 with regular, for the premium I got 6.8l/100km and with the regular I get 6.8l/100 km that is pretty much all highway driving at 120kph, up hill one way and down hill on the way back (for the most part) when I put the off road tires on that number for regular changed from 6.8 to about 7.6L/100km..

how are you getting in the 12's.. I am only high 8's with all town driving..

Did You mean predetonation?

 

[jkernitzki]

So I'm going to be "that guy".

"Predetonation" is a misnomer. There's preignition or detonation. Two different phenomenon, and completely separate in sequence.

Preignition occurs before the plug fires, and involves an uncontrolled ignition source, like a hot carbon deposit or overheated spark plug. This is similar to dieseling, though not precisely the same.

Detonation is better known as "knock", and occurs after the spark plug fires. The fuel-air mixture ignites in pockets as the flame front approaches, causing high-pressure shockwaves. This can be caused by the same things as preignition.

Germane to the topic here, in general the higher the octane the greater the resistance to both conditions. However, modern fuel injection and ignition systems have virtually eliminated both conditions independent of octane. Fuel/air mixture and ignition timing are dynamically adjusted to reduce carbon buildup (too rich) and excessive combustion temps (too lean) as well as keeping spark timing advanced or retarded appropriately for the conditions.

 

[Mark S.]

However, modern fuel injection and ignition systems have virtually eliminated both conditions independent of octane. Fuel/air mixture and ignition timing are dynamically adjusted to reduce carbon buildup (too rich) and excessive combustion temps (too lean) as well as keeping spark timing advanced or retarded appropriately for the conditions.

A couple of nits:

First, it's not carbon buildup or combustion temps the computer is controlling for, it's cylinder pressure. Detonation increases cylinder pressure, which if allowed to go on too long can increase head temperature and damage rings and piston skirts. Reducing excess carbon buildup is a beneficial side effect of controlling the mixture, but the main goal of dynamic engine control is to avoid high cylinder pressure.

Second, the computer monitors knock sensors installed on the engine to know when and how much to adjust mixture and timing. That means there must be SOME degree of knock before the computer can make adjustments. Light--or even moderate--detonation is not particularly harmful to an engine assuming it's not frequent (in the case of moderate detonation) or sustained. As long as the computer makes an immediate adjustment when the knock sensor fires your engine will be fine--it's designed to function that way.

 

[jkernitzki]

A couple of nits:

First, it's not carbon buildup or combustion temps the computer is controlling for, it's cylinder pressure. Detonation increases cylinder pressure, which if allowed to go on too long can increase head temperature and damage rings and piston skirts. Reducing excess carbon buildup is a beneficial side effect of controlling the mixture, but the main goal of dynamic engine control is to avoid high cylinder pressure.

Second, the computer monitors knock sensors installed on the engine to know when and how much to adjust mixture and timing. That means there must be SOME degree of knock before the computer can make adjustments. Light--or even moderate--detonation is not particularly harmful to an engine assuming it's not frequent (in the case of moderate detonation) or sustained. As long as the computer makes an immediate adjustment when the knock sensor fires your engine will be fine--it's designed to function that way.

All correct, I probably oversimplified things, or at least stated it poorly. Decreased carbon and temperatures are a result/byproduct of modern FI & ignition systems, not what is being monitored.

It’s the same as oiling a pan to fry a steak; the purpose is lubrication, but the result is searing (which some would argue is the point. )

 

[Stircrazy]

The few station in the Midwest near me only have ethanol free in 91. I run that in my mowers and motorcycle. I’d run ethanol free 87 if they had it. Also, people should take note if it’s a single hose pump with multiple grades. The first 1/4 gallon or so will be what ever the last person used.

ya the only way to get ethanol free up here is to buy 94 and only a couple of the gas companies have it, the rest there is ethanol in it so its hard to find unless a local place near you has ethanol free. there used to be a lot of 91 that was ethanol free but that went by the way side years ago.

 

[Stircrazy]

Did You mean predetonation?

haha stupid spell correct, I didn't even know it slipped one in there

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