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The car in question is my 'new to me' XF-R, a '13 MY facelift. The first owner was filling up with regular petrol which is 91Oct+E10 here, I've driven the last 2000 miles filling with 97 octane and its caused my gas consumption to increase, I'm not sure if the performance has improved or degraded with the change of fuel though.
Could the mileage drop be related to the fuel used?
Could I use both 97 and 91+E10 safely without causing harm to the engine? 97 isn't widely available here.
Where is 'here'? It's nice to know what part of the planet you're on, as fuel rating systems and engine calibration varies from one market to another.
As you used the word 'petrol' instead of 'gas' I'll guess that you're not in North America. If so, your fuel is probably rated using the RON system. Your owners manual will state the minimum recommended octane level, probably 91 AKI/95 RON.
Odd... I don't think we have 91RON at all - so not sure where the OP is!
Car makers tweak the software (calibrations) per market / region so read the handbook and use what it says. My Jag actually has an OE sticker by the fuel filler saying the minimum (95RON) to use.
I don't know about the anemic 3.0's and 2.0's, But the V8 requires the highest top tier gasoline you can find..A fuel blended with 10% Ethanoil will decrease mileage as it has a lower BTU content, so therefore the engine uses more to get the same bang for the buck as 100% fuel
I use only Shell Premium at the octane rating of 91..which pisses me off, because that is the highest I can find in my area...I want 93 octane at least, for optimum engine performance.
The car in question is my 'new to me' XF-R, a '13 MY facelift. The first owner was filling up with regular petrol which is 91Oct+E10 here, I've driven the last 2000 miles filling with 97 octane and its caused my gas consumption to increase, I'm not sure if the performance has improved or degraded with the change of fuel though.
Could the mileage drop be related to the fuel used?
Could I use both 97 and 91+E10 safely without causing harm to the engine? 97 isn't widely available here.
Here's an interesting gif that talks about the inner workings of an engine. The octane section has some really interesting info that is pertinent to this.
EDIT: Apparently you can't upload a gif, so I'll just type out the relevant info.
"Using higher octane fuel in an engine designed for lower octane simply wastes money and can result in less complete combustion, resulting in lower fuel mileage.
Gasoline's octane rating refers to its resistance to autoignition.
Autoignition occurs when the fuel-air mixture is ignited by compression alone, without any spark. This can contribute to engine knock and is generally destructive. High performance engines often have higher compression, which requires higher octane fuel to prevent autoignition. "
In short, if you're using an octane other than what the engine was designed for, you *may* see decreased mileage.
Last edited by n8ertot; 11-01-2015 at 12:19 PM.
Reason: Added info.
91 octane not RON, European octane. I'm from India. The manual doesn't specify permitted Ethanol content. I think 95RON is what's recommended for the XF-R.
91 octane not RON, European octane. I'm from India. The manual doesn't specify permitted Ethanol content. I think 95RON is what's recommended for the XF-R.
European octane rating is the RON system, which I believe India follows. If so, use fuel that is 95 RON or higher to obtain full potential.
Don't worry about 10% ethanol (E10). All Jags built in the last 20+ years can use it. Loss of power and fuel economy is approximately 3%.
I don't know about the anemic 3.0's and 2.0's, But the V8 requires the highest top tier gasoline you can find..A fuel blended with 10% Ethanoil will decrease mileage as it has a lower BTU content, so therefore the engine uses more to get the same bang for the buck as 100% fuel
I use only Shell Premium at the octane rating of 91..which pisses me off, because that is the highest I can find in my area...I want 93 octane at least, for optimum engine performance.
The fuel door sticker on my XFR says 91+.
Where in OKC are you I always put ethanol free 93 in my STi while we lived in Edmond.
RS fuel off the turnpike near May has 93 without Ethanol however it is about $1 more than ethanol free 91.
Where in OKC are you I always put ethanol free 93 in my STi while we lived in Edmond.
RS fuel off the turnpike near May has 93 without Ethanol however it is about $1 more than ethanol free 91.
South side...sw119th and May....we use to have a Sinclair at I-44 and sw 134th that sold pure 93 octane..but haven't seen one since..you'd think SHELL would have it at least..91 is at the bare minimum you want to use.
As for Octane ratings, it's confusing on an international forum, people should really be clear if they are talking about AKI or RON numbers.
In any case an E10 91RON is not what i'd be running in an XFR... the engine management will adapt but it's not exactly a "premium unleaded" which is what these engines demand. Minimum 95RON would be the usual recommendation! (equivalent to 91AKI)
You saw an increased consumption changing from E10 91RON to straight 97RON? That's the opposite of what would be expected...
Unless you've been enjoying an increase in power and using your right foot a bit more...
I did a little digging and confirmed that the octane ratings of petrol/gas in India are expressed in RON. I also found that only two grades are commonly available, the 91 and 97 RON mentioned by the OP, with nothing in between.
These ratings are roughly equivalent to 87 and 92 AKI. The 2013 XF/XFR owners manual, at least for North America states the following:
OCTANE RATING Premium unleaded gasoline with a Cost of Living Council (CLC) or Anti Knock Index (AKI) octane rating of 91 or higher should be used. .... Using unleaded fuel with a lower than recommended octane rating, can cause a persistent, heavy engine knock (a metallic rapping noise). If severe, this can lead to engine damage.
Note: Mid or regular grade gasoline with a CLC or AKI octane rating of not lower than 87 may also be used, but performance and fuel economy will be reduced.
You saw an increased consumption changing from E10 91RON to straight 97RON? That's the opposite of what would be expected...
...
Exactly...I as an experiment ran 10% ethanoil in my lawn mower..I had to fill the tank twice to cut my entire yard...back on 100% pure gasoline, One tank to cut the whole yard and still had some left over in the tank..
3% difference is a very conservative number as far as mileage difference...I think it is more along the lines of 7% to 8% in most cases..So it makes perfect sense to buy and pay per unit a little more of 100% vs E10, as you can go further but fill up less, so the cost is about the same over all and it's better for all of the engine's concerns too..To say the engines can handle Ethanoil is just asking for future trouble throughout the fuel system.
Has anyone done any testing on the track or dyno with an XF or XFR indicating that 93AKI actually produces more power than 91AKI?
Paying a buck a gallon more for ethanol free in order to gain 3% mileage/power makes little sense.
Considering the tune on my STi was for 93 it did make sense. Not to mention I noticed a tremendous difference on the butt dyno between fuel with ethanol and non ethanol. Also the car was drove a few times a week meaning I only filled up max a few times a month.
Exactly...I as an experiment ran 10% ethanoil in my lawn mower..I had to fill the tank twice to cut my entire yard...back on 100% pure gasoline, One tank to cut the whole yard and still had some left over in the tank..
3% difference is a very conservative number as far as mileage difference...I think it is more along the lines of 7% to 8% in most cases..So it makes perfect sense to buy and pay per unit a little more of 100% vs E10, as you can go further but fill up less, so the cost is about the same over all and it's better for all of the engine's concerns too..To say the engines can handle Ethanoil is just asking for future trouble throughout the fuel system.
When we lived in Denver the terrible gas damn near killed my mower, once we moved to OKC and I started running ethanol free gas it ran just fine.
3% difference is a very conservative number as far as mileage difference...I think it is more along the lines of 7% to 8% in most cases..
Ummmm, no.
While some parts of the world only recently started using E10, it's been in common use elsewhere for 30+ years. In many areas, the only thing new are the labels on the pumps advising consumers of the ethanol content. The fuel itself didn't change.
I've been using E10 for over 20 without a single issue. In that time, I've accumulated sufficient data that proves the real-world loss of mileage is ~3% which matches the calculated loss quite accurately.
This is slightly more credible than mowing the lawn once.
Much like the ill informed predictions of doom and gloom when lead was removed from gasoline, I'm sure the E10 myths will still be around 30-40 years from now.
11-01-2015, 01:13 AM
What fuel to use?
