Dodge Caliber Forums banner

1 - 20 of 359 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter · #1 ·
I purchasd an 07 SXT 1.8L 5-speed back in August.
Right now I have about 3600 miles on it and consider it fully broken in.

I work in Indianapolis, IN, Monday-Friday and go home to Columbus, OH for the weekend. I use premium 92 or 93 whatever the top unleaded gas the station has. For the last few trips I have been getting a tad over 36 MPG. This is 100% highway, straight shot on I-70 and 100% doing 60 the entire way with cruise on. It sucks becuase I'm getting passed by busses and semi's and geo metro's, but I dont care. I was still suprised I was able to get over 36MPG though. How is everyone else faring?

Nathan
 

·
Registered
Joined
·
154 Posts
I'm averaging 30-33mpg, but still babying it. You will get better mileage if you maintain a consant speed on the highway.
 

·
Registered
Joined
·
68 Posts
I have a 1.8SXT as well and I'm lucky to break 26. How can there be a 10 MPG difference? I do have a roof rack but at most there should only be a 2-3 MPG change.
 

·
Registered
Joined
·
1,707 Posts
You'll get better gas mileage running 87 octane. No need to run the premium. It's just a waste of money, unless your motor needs it to keep from detonating
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #6 ·
99.99% of the time I would agree with you that running 87 would give me better gas mileage, as that has been the case with every other vehicle I have ever owned. But for some reason I do get better mileage with the premium gas. I have run a half dozen trips each with 87 and 92/93 and in every case got better with the 92/93. And before you ask the variables were the same, 100% highway, 60MPH entire way with cruise, no other factors.

Ideas as to why this is?
 

·
Registered
Joined
·
168 Posts
naterhit said:
99.99% of the time I would agree with you that running 87 would give me better gas mileage, as that has been the case with every other vehicle I have ever owned. But for some reason I do get better mileage with the premium gas. I have run a half dozen trips each with 87 and 92/93 and in every case got better with the 92/93. And before you ask the variables were the same, 100% highway, 60MPH entire way with cruise, no other factors.
Ideas as to why this is?
Not meaning to start an argument here, but the only idea I would have as to why this is would be your own subjective perception.

A very good friend of mine made the same "I swear it's true" statement about a year ago and wouldn't believe me when I told him he was delusional. So we set up a journal. Every time he went for gas he would fill the tank and note the amount of fuel and the mileage on the car. After three weeks we figured he was running about 21mpg (this was in a van, btw). For the next three weeks he did it again, this time with premium fuel, and when we figured that out he was running about 21mpg again -- and this was figured AFTER my friend swore again that he wasn't refilling the tank as often.

Perception is a powerful influence against objective data. Many people want to believe that their 87-octane-engine is running smoother or putting out more power or getting better mileage because they spent more money on expensive fuel, but there is absolutely no empirical data or other evidence to back this up.

Increased octane contributes exactly zero percent towards gas mileage on an engine that is designed for lower-octane fuels. If you have an engine that requires 87 octane fuel and promises 35mpg, you'll get 35mpg regardless if you put in 87, 89, 91, 93, or one billion octane.
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #8 ·
Sgodun,
I respectfully disagree with your statement. I tend not to be a subjective person when it comes to things like this. I'm not one of those people who state this mod has more kick in the pants than that, etc etc. I am an engineer by trade and have to be very methodical. In all other vehicles I have owned ( 1st gen neon r/t, 2nd gen neon r/t, intrepid, etc etc ) the 87 did not only give equal but in most cases gave BETTER gas mileage than with the 92/93.

In this car though I have my journal and logs of when to fill up. Every weekend I make a round trip from Indy to Columbus and get plenty of driving.
I do not drive my car on during the week nor make any other trips. Before I leave for the weekend I fill up, hop on the highway, set cruise at 60, and a few hours later arrive at my house. No factors such as traffic, stops, etc. About the only variables are temperature, and wind.

I have made probably 10 round trips and there is a couple MPG difference with the better gas. I usually get 35-36.5 with the premium gas and about 33.5-34.5 with the standard 87.

Ideas?
 

·
Registered
Joined
·
168 Posts
As I said, increased octane contributes exactly zero percent towards gas mileage on an engine that is designed for lower-octane fuels. This isn't my experience or my opinion. It's just a fact. (OTOH, if you've got an engine designed for higher-octane fuels and you feed it lower-octane fuel, you will lose mileage due to detonation and related issues that result from using the lower-octane fuel.)

There are two other possibilities that I can see.

Possibility #1 is that your premium gas is not oxygenated (or is "less" oxygenated) but your regular gas is (or is "more" oxygenated). This would cause your fuel system to inject a greater volume of fuel when using regular gas versus premium gas, and therefore would reduce your mileage.

Possibility #2 is that the regular gas you're getting is dirty or otherwise contaminated and therefore not burning as efficiently which could conceivably result in a difference in mileage.

I would be mildly curious to see the results of an emissions test of your vehicle using premium versus regular fuels. I suspect you'd see an increase in hydrocarbon emissions when running regular.
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #10 ·
I suspect your possibility #2 is probably more correct. I have used several stations though and the results are the same.

I used to work at a gas station in college on the midnight shift to pay for...well...bad habits lets just say. The owned told me that although all the gas holding stations underneath are supposed to be all equally clean, however the 92/93 will always be the cleanest. When I asked why the reason he gave was the 87 is generally sold 2-3X more frequently than the 92/93 and hence will go through a larger amount quicker. The station I was at I believe had 10,000 gallon tank for the 87, 7,000 gallon for the 91, and a 5,000 gallon for the 93. He stated that the 87 would be filled at regular intervals when the refueling tanker came ( every Tuesday and Thursday i.e ) and would fill it up no matter how much it needed. Now the 92/93 on the other-hand he stated would only be filled when it was at the very minimum allowable. He said they needed to maintain some in there at all time, but it was nominal. I figured it was for vacuum pressum or something. Anyway the sediments and impurities in the 87 will sink to the bottom and settle. It will be settled up again and stirred up when the tanker comes. The 92/93 generally has all these impurities removed as the gas is pumped out closer to being emptied.

If I had to guess I'd say it was #2, then again maybe thats the case for all the stations with 87. I am gettin 1-2.5 more MPG with the 92/93
 

·
Registered
Joined
·
168 Posts
That's why I have a pre-filter in the fuel neck of my car. :)

Even so, the point remains: You aren't getting better fuel economy because you're running premium fuel. You're getting better fuel economy because you're running cleaner fuel. Octane has nothing to do with it.
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #12 ·
I'd beg to differ since this is the same data collected from almost a dozen different gas stations being filled up at. I dont know if that is true as far as the cleanliness of the tanks, thats what I was told by 1 gentleman.

Do you know for a fact that our ECU's do not take advantage of advanced timing or benefits of better octane?
 

·
Registered
Joined
·
59 Posts
sgodun said:
There are two other possibilities that I can see.

Possibility #1 is that your premium gas is not oxygenated (or is "less" oxygenated) but your regular gas is (or is "more" oxygenated). This would cause your fuel system to inject a greater volume of fuel when using regular gas versus premium gas, and therefore would reduce your mileage.

Possibility #2 is that the regular gas you're getting is dirty or otherwise contaminated and therefore not burning as efficiently which could conceivably result in a difference in mileage.
How about Possibility #3 -- Chrysler "designed" the caliber for a minimum 87 octane, but in reality, they're running a bit more spark than that. As a result, the knock system pulls out some spark on 87 and results in worse fuel economy. Given the various knock complaints, it seems DCX may have a bit more agressive spark than 87 will tolerate...
 

·
Registered
Joined
·
168 Posts
naterhit said:
I'd beg to differ since this is the same data collected from almost a dozen different gas stations being filled up at. I dont know if that is true as far as the cleanliness of the tanks, thats what I was told by 1 gentleman.

Do you know for a fact that our ECU's do not take advantage of advanced timing or benefits of better octane?
It's pretty interesting how you come up with these new "facts" (actually, heresay) every time a new point of order is brought up. To use your own experience: What does it matter if it's a dozen different gas stations if all of them have "dirty" gas according to your own experience? I mean, if the gas station you worked at was a representative example then it stands to reason that other gas stations would have similarly dirty tanks.

Do I know for a fact that our ECUs do not take advantage of higher octane? Yes, I know it for a fact. How? Becase I know for a fact that there is no "octane sensor" in the vehicle. I also know for a fact that if Dodge had an engine that offered different power and/or fuel economy ratings for different octane ratings, that information would absolutely be readily available to the general public. Dodge would be advertising the bejeezus out of it, not to mention the fact that the EPA would need to publish multiple test results for mileage based on different octane ratings. Since there's no advertising, no documentation, and no EPA information, I think it's a pretty safe bet to say that the ECUs don't take advantage of higher octane.
 

·
Registered
Joined
·
168 Posts
Tito said:
How about Possibility #3 -- Chrysler "designed" the caliber for a minimum 87 octane, but in reality, they're running a bit more spark than that. As a result, the knock system pulls out some spark on 87 and results in worse fuel economy. Given the various knock complaints, it seems DCX may have a bit more agressive spark than 87 will tolerate...
See previous response. If the vehicle was capable of different fuel economy with different fuels (octanes) then by law there would have to be an EPA rating to cover the different octane ratings. Ever see a flex-fuel vehicle? They often have two or three EPA ratings attached to them, each based on a different fuel type. The same principle applies here.

On top of all that, just think in terms of sheer marketing power. Dodge advertises the Caliber at 32mpg highway. Do you REALLY think that Dodge would DOWNPLAY the mileage of the car in their advertising?

I don't doubt that the OP is getting upwards of 36mpg with his car. EPA ratings are always ±5mpg and if they're showing 32mpg then even 37mpg isn't out of the question. What I doubt is the OP's claim that the octane change is making the difference. I'm willing to buy that he's been getting dirty and/or poorly oxygenated fuel; there's science to back that up. But there's no science that supports the claim that adding octane improves fuel economy. None, zero, zip, nada.

If the OP wants some real answers he should perform some controlled tests. Get a smog test on the car with the different fuels, for example. Load up on regular and toss in a bottle of octane boost. If what he says is true then he should be able to AT LEAST match the fuel economy of premium by using regular+octane boost.
 

·
Registered
Joined
·
37 Posts
I'm getting roughly 35 with my SXT on the highway with the cruise at 65, so i would probably get the same as you if i dropped my speed a few mph.
 

·
Registered
Joined
·
340 Posts
I am no scientist but I can safely say that the higher the compression ratio is -- the higher rating of octane you need.

I CANNOT run anything less than 110 race fuel in our 13.5 race engine. It will detonate and get VERY hot quickly (read at each header tube, thats how we make sure each cylinder is making the correct amount of power) and also make much less power. I also cannot run 106 octane in the 10.1 street motor, it fouls plugs and runs terrible because it does not have enough squeeze to fire the high octane. It runs 94 with an occasional 1/2 gallon of 110 works perfect.

Granted this has no direct relation to the Caliber, but if it was designed to run on 87 octane and it was TRUE clean 87 octane gas, then it should get the rated MPG. But, it seems many Calibers are detonating on 87 and need the 92/93 to be quiet. Which might be why some cars are getting better mileage than others. When you have the optimal octane rating for an engine it will deliver it's best power and performance (supposedly that is).

Again, I am no scientist nor EXPERT on gas for that matter!
 

·
Registered
Joined
·
48 Posts
hmmmm.. someone needs to ask Dodge about this. If we can run a higher octane and get better milage, i would be all for it.
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #20 ·
No I haven't tried running midgrade, but I do get better mileage with the premium opposed to the low leve stuff. Might be dirty gas, might be Dodge design, who knows what. But I can honestly say that it is always a couple mpg better with the premium
 
1 - 20 of 359 Posts
Top