Octane for hot weather

[tamedcowboy]

I own a 2015 Ford Focus SE, and although the owner's manual recommends 87 octane, max power figures are quoted at 93 octane (maybe because the compression ratio is 12 to 1?) I normally run 87 octane, but wondered if I should run 93 now that the temperature is over 100. The car runs perfect with 87 but I wondered if 93 would be better when it's over 100 degrees, to prevent pre-detonation, and especially with higher AC loads. Thanks for your input!

 

[Eddie]

Probably no need to use higher than 87 but, try a tank and see if you notice any difference. Report back. Ed

 

[Alex_V]

Is it direct injection? 12:1 seems high not to be. If it is, I don't think pre-detonation is an issue and I'm not sure how octane affects little DI engines. However, I have a '13 Cruze (1.4L turbo, port-injected 4 cyl. w/9.5:1 compression) and there's a marked difference in behavior between 87 and 89 octane. That said, through repeated experiences with modern, and old (carbureted) vehicles, I refuse to burn regular unless I'm in the middle of nowhere and I that's all that's available - performance, engine cleanliness, fuel economy, etc., I have several reasons. Absolutely, try other grades and see how your performance and economy benefit, but even 89 is better than 87.

 

[tamedcowboy]

You're right. The higher octanes have better detergent packages. I'm gonna try 93 and see how it does. And yes it's DI.

 

[sciphi]

It might be a bit peppier if it doesn't have to knock back timing as much running loaded with A/C in the heat. Give it a try and see. My turbo Cruze definitely runs better on 93 than 87. That 1.4T engine is well-known for that trait, though.

 

[gathermewool]

What's the source for max power on 93 octane?

Might it be listed for the turbo-charged ST, not your NA engine?

I find it hard to believe 93 would benefit in the slightest. Heck, not every state even offers 93 as their premium, and not even every 91 premium is created equal.

 

[Colt45ws]

With high compression/direct injection higher octane can be a huge help. It may even get better mileage.

 

[SZR48207]

Is it 93 as the US R+M/2 method? I've seen this topic confused when the octane rating in the book is for other countries where the octane ratings are different.

See here: http://www.pencilgeek.org/2009/05/octane-rating-conversions.html

 

[Colt45ws]

Actually, Im looking at the specs, and its only showing that little * for the power rating next to the Ecoboost turbo engines. Not the NA GDI 2.0L. So its power rating is on 87. Whereas the note for the * reads "tested on 93 octane"
This tells me the non-ecoboost engines are power rated on 87.

http://www.ford.com/cars/focus/specifications/engine/

 

[Jetronic]

or 89, or 91...

 

[skyactiv]

Originally Posted By: gathermewool
What's the source for max power on 93 octane?

Might it be listed for the turbo-charged ST, not your NA engine?

I find it hard to believe 93 would benefit in the slightest. Heck, not every state even offers 93 as their premium, and not even every 91 premium is created equal.


Ford has published horsepower numbers on the Focus with 87 octane and either 91 or 93 octane in the specs on their website for the non ST GDI Focus. They pulled the specific detailed info for 2016 models. They do however quote horsepower figures with 93 octane on some models, but no longer quote them along with 87 octane which is less.

A few automakers have said our addiction to 87 octane results in them giving us engines with less power and fuel economy. Mazda's Skyactiv 2.0 in Europe has a point higher compression because they don't have crummy 87 octane gas to destroy it.

 

[The motor guy]

I'm not sure if there is enough of a difference to negate the higher price. I think it's usually .25 cents a gallon higher for mid grade

 

[MuzzleFlash40]

The compression ratio is 11.5 in her Santa Fe D.I engine. I know I see a 1-2 mpg difference with using 89 octane over 87. Also feels better as well.

 

[tamedcowboy]

Well I've ran 2 tanks and my fuel economy went up from 36.5mpg to 37.1. Car feels peppier too. I'm impressed!

 

[dailydriver]

Originally Posted By: skyactiv
They do however quote horsepower figures with 93 octane on some models, but no longer quote them along with 87 octane which is less.


^^^THIS

Ford tells you right in the text of their brochures for the Fiesta ST's 1.6 turbo direct injected engine that the stated HP and torque figures were attained on 93 octane fuel, and will be less on lower octane level fuels.

 

[Benzadmiral]

I drive w/ AC on in some very hot afternoon temps for a good part of the year. Naturally I experimented with 93 earlier, to see if the Regal's fairly high compression engine (11.2:1) would respond to the extra octane. It did -- seemed a bit "peppier," and gas mileage increased a fraction -- but not enough to pay for the increased cost of the 93 over 87.

That said, I might try it again this summer, understanding it won't pay for itself but to see if the car responds a bit better. I'm not sure if the Shell V-Power in my area is 93 and E0, which might well be worth my while. The few "premium" gasolines I see that trumpet their lack of ethanol around here are all 90 octane (while demanding the same price as other premiums).

 

[sciphi]

Originally Posted By: tamedcowboy
Well I've ran 2 tanks and my fuel economy went up from 36.5mpg to 37.1. Car feels peppier too. I'm impressed!


Sorta figured you would be with higher octane in this engine. 94*F weather here today, and my 1.4T Cruze running 93 octane was acting normal for itself in hot weather.

Originally Posted By: Benzadmiral
The few "premium" gasolines I see that trumpet their lack of ethanol around here are all 90 octane (while demanding the same price as other premiums).


I've tried 91 octane E0 and 93 octane E10. The engine noticed the lower octane. The 93 octane E10 gave better fuel economy and responsiveness than the 91 octane E0.

 

[HerrStig]

A little carbon in the combustion chamber can kick the requirement up a notch or two. High miles Toyota I4 engines often run slightly better on 89, despite the 87 rating in the book. 89 avoids the knock sensor pulling the timing back when running 87. I have not found anything higher than 89 to make a difference in these engines. ( I have several) I have read, however, that the 3.5 V6 motor optional in the latest Camrys, which is rated at 285 hp on 87 will produce at least another 5 hp on 89 or above.

 

[tamedcowboy]

Yeah, my Focus at 12:1 seems to respond to 93 in hot weather. I use Shell V-Power as well. My fuel economy went from 36.5 to 37.1, and the car does feel a bit peppier. If nothing else running 93 all summer will keep my injectors clean. After Labor Day I'll probably switch back to 87.

 

[tamedcowboy]

Thanks for the info. My experience is the same. Didn't think it would make a difference but 93 octane does, at least in hot weather. I use the Shell V-Power.