jedijeb

Colder denser air is normally preferred by drag racers for giving more power, on newer vehicles the system should compensate and not lose much mileage at all. I would think in my carburetor it would run lean instead of rich since it meters fuel by volume and there would be more air versus fuel at colder temps.

One thing I just thought about, is fuel shrinkage. Since the storage tanks are underground, the fuel comes out of the ground at near 50F and goes into my tank below 20F, it will lose volume after pumping it, which is natural for gasoline. Matter of fact a truck stop near here got in trouble for using tank heaters to heat the diesel fuel to bias the pumps to show more fuel being delivered than what you were actually getting once it hit the truck tanks at ambient temperature.

black label

So true. Octane is all about how combustible the gas is under pressure, if you have a low compression engine like a jeep 4.0, there is no performance benefit with high octane.

High octane gas doesn't make high performance engines, high performance engines are often high compression and want the high octane fuel so the fuel doesn't combust in the compression stroke.

107 octane fuel doesn't turn a chevette into a corvette.

Fwiw, ethanol had a higher octane rating (about 113) than petrol does. If you take 87 octane petrol an add 10% ethanol, you end up with a fuel that is actually higher than 87 octane, yet contains less energy than pure 87 octane petrol with no ethanol added. In short, higher octane doesn't mean more energy, it just means less combustible under pressure.

spiral_energy

soooo from what i can tell shell gas is more expensive but they don't advertise 10% ethanol. or is that a federal law? should i go to 93 octane since thats advertised here with no ethanol?

jedijeb

As stated above it doesn't make much difference unless you raise your compression ratio, but I do run a tank full through every now and then because the additives help clean out the fuel system.

On my F150 I do have to move up to mid grade to eliminate pinging, but I think that is caused by carbon deposits more than anything, but on regular when I am pulling up a hill it will sound like a diesel, with the mid grade it doesn't.

black label

That's a tricky question. The extra octane would be a bit of a waste, but no ethanol could have a benefit as ethanol decreases the energy the fuel provides.

I'd he curious what your mileage was with the 93 vs 87 as well as what the extra cost would be. It's possible that the 93 with no ethanol would increase mileage enough that it became less expensive to operate on but I doubt it would work out.

16 gallons of 93 would be about $4.00 more expensive than 16 gallons of 87. $4.00 would buy about 1.2 gallons of 87, would you get more mileage out of 16 gallons of no ethanol 93 octane or 17.2 gallons of 87 octane E10? (This is all based on fuel prices in my area, your results may vary)

93 octane with no ethanol would have more potential energy than 87 octane with 10% ethanol but I'm not sure it would yield enough real world fuel savings to be more economical.

zombiehunter99

Im here in ohio and I noticed my mpg went down. Went from 17-20 down to like 13. I thought something was wrong with my xj cleaning sensors and throttle body. My iac port was caked with carbon deposit. Glad i found this post because I thought my jeep was broken lol actually with winter this fuel is breaking my wallet...

spiral_energy

Gas here decided to spike up by 40 cents

jedijeb

Here for me it is hit or miss, mostly miss lately on prices. I filled up for $3.38 then drove to the next town over and it was $3.18

My mileage now dropped below 12mpg even with a stretch of nice weather with shorter warmups in the morning. I mean a 2.5L, mostly back roads at 55mph and only a little city driving(5 stoplights through town) and it was getting 18-20mpg in the summer. Something is seriously wrong when switching to winter blend causes that much trouble.

s346k

I'd guess it has to do with the air more than the fuel. hotter air/fuel burns much easier. I run 93 oct in my jeep all the time. I am now tracking my mileage as a friend of mine with an xj seems to think I'm getting 13 mpg. I'll report back with my findings. I do know if we get another foot of snow like they're predicting it will hurt my mpg. I have a problem with flooring it all the time in the snow.

Fred/N0AZZ

You bet it is and the Governor here in MO. pushed it also for O'Bammer and drove up feed prices for cattle/hogs/chickens and it showed up in availibilty and prices.

When that S**T hit I ended selling cattle right off of pasture instead of feeding for 3 mo. as I had always done. Corn prices didn't come up to the price of fat cattle.

Fuel mileage always goes in both directions in summer/winter different blends and what state your in.

black label

I was always under the impression that cold dense air provided more power from the engine, this is the basic reason for an inter cooler on a turbo engine, to chill the air and make more power. It's also why a fmic works better than a tmic.

I think the cold has an effect on mileage in other ways, cold lubricants will have more resistance, more resistance means more effort to move those lubricated parts.

Cold airs density will also have an effect on a Cherokees already poor aerodynamics as the denser the air, the more resistance it provides.

13 mpg is what I get when using 4wd high, it's shocking (to me at least) how much mpg I lose with 4wd over 2wd. Powering all 4 causes a 30% loss of fuel economy for me.

s346k

i understand how cold air makes hp. more hp = more fuel use.

ive read about the hyper milers preheating the air and fuel so it is easier to burn. kind if interesting, we all want cold air/fuel and more hp haha

FTHESHACK

Gas prices are up about 30 cents here in N. Texas and my mileage has dropped about 3-4 mpg. The only way I can see getting ethanol out of our fuel is to vote its supporters out of office and make it well known why they lost their jobs. Seems the only time Gov't hears the ppl is when their livelihood is in jeopardy.

F1Addict

Most XJs have a 20 gallon tank but use only 17 gallons before scaring their owner into filling up. The figures below are based on current Southern California gas prices ($3.79/$3.89/$3.99) but the higher octane, non-ethanol fuel would result in around a 10% savings if it improved fuel economy by 2 mpg. This, of course, is dependent on the price differential between the two grades of fuel. I know there's a bigger gap between the two in some areas and a smaller gap in others.

17 gallons 87 octane ($3.799) @ 13 mpg = $0.292 per mile
17 gallons 92 octane ($3.999) @ 15 mpg = $0.267 per mile



Jedijeb is claiming his economy dropped from 18-20 mpg to 12 mpg. Assuming an average loss of 7 mpg and assuming ethanol-free fuel would correct this...

17 gallons 87 octane ($3.799) @ 12 mpg = $0.317 per mile
17 gallons 93 octane ($3.999) @ 19 mpg = $0.210 per mile

Around 30% savings using the more expensive, non-ethanol fuel.

s346k

lol. let's rag on ethanol because we drive inefficient engines that are inherently susceptible to poor fuel mileage. barring all the bs, ethanol is an amazing fuel offering way more pros than cons. however, I digress..