I get 16 mpg on the grocery store gas, 85 octane at 6000 ft. Tried running mid-grade 87 octane = no difference.

 

I was just trying to give a comparison to some thing our Canadian friend might be more familiar with. Now, some Super HEBs are like Wal-mart minus the sporting goods section. Have you ever been to a Super HEB? I have an HEB about a mile from my apartment, but it's just a regular grocery store.

 

Texaco.

 

Well i got 240 Miles on 12.134 gallons according to fillup today.


Do the math.

 

I have noticed exactly the same thing when filling up from Valero (formerly Diamond Shamrock). My driving habits are on the conservative side. Mostly under 2K on the tach. When using Valero's fuel, my mpg plummets. I haven't noticed this type of mpg variance with any other brand of gas. Usually I can get about 415 miles out of a tank, but with Valero that's cut to about 350.

addressing the myths about higher octane fuels. octane is added to gasoline to prevent premature detonation in high compression engines. octane does not increase gas mileage! higher octane prevents engine damage in high compression engines like LS7's (11:1 ratio). using higher octane fuels in lower compression/un-tuned engines is just a waste of money.

 

I can get up to 118-119ish kilometers per hour and be right on 2000 rpm. I have 373's as well.

118 divided by 1.6 = 73.75 mph

At 120 kmh which is 75 mph, I'm reving close to 2100 rpm.

As for my fellow Canucks, I agree. Esso seems to do just fine.

 

Not to start a pissing contest, because I have gotten into enough of those in the past 8 hrs. I have done the comparison between the 87/89/91/93. I can assure you when I use 87 I get about 12-13 mpg. on 89 14-15, and 91&93 between 15 and 18 18 when on hwy, and usually 16 with mixed. I run normally sunoco and shell. And the citgo gas is the worst even there"high performance"

 

While not disputing your individual findings and certainly not interested in a pissing contest I would say that your results are not consistent with my education on this matter.

For instance a citation from Chevron's site:

Don't Buy a Higher-octane Gasoline to Improve Fuel Economy

Octane and energy content are not related. Premium-grade gasoline doesn't necessarily have a higher energy content, especially if it is oxygenated.

The exception to the above advice is when a lower-octane gasoline doesn't satisfy the octane requirement of the vehicle's engine. The abnormal combustion that announces itself as knocking reduces engine efficiency. Using a higher-octane gasoline that eliminates knocking will improve both engine performance and fuel economy.

Many newer vehicles with an electronic control module (ECM) also have a knock-sensor device. When the sensor detects knocking, the ECM retards the engine's ignition timing to eliminate the knocking. This happens so quickly that the driver never hears the knocking. But retarding timing decreases power and fuel economy. A higher-octane gasoline may improve the performance of knock sensor-equipped vehicles that have less power than when new.

http://www.chevron.com/products/prod.../fuel_economy/

Octane stabilizes gasoline and prevents spontaneous detonation due to excessive compression. People often confuse the point because high performance engines, generating high horsepower require high octane fuels. Not because high octane fuels have more power, but rather because they perform better under pressure.

 

Something doesn't sound right with your truck then. I have an '04 with 3.73's, and I'm running just under 75 at 2Krpms. Searched and found a link where another member is running 4.10's and he's at just under 2K /60mph.

 

You gave the potential answer right there in your Chevron quote. If someone's particular truck tries to knock on lower octane gasoline, either due to the characteristics of their particular engine, their driving style, or the load they are pulling and terrain they are in, they will never hear it, the timing will be retarded, and they will lose power and fuel economy. There are so many variables at work, not to mention how closely any particular brand or batch of gas actually meets the octane rating stated on the pump, that I could definitely see where some folks would get better mileage with higher octane.

 

Yeah, I think I exaggerated a little on that comment. I'm about at 2K RPM around 70 mph. Now I know I'm over at around 75 mph and at 80 I'm about 2200 rpm.

I've been getting 16 mpg now on the hwy using Shell gas towing a small trailer in Colorado to boot. I've never gotten this good of mileage. I think it's the quality of gas that makes the biggest difference, but premium here is only 90 octane. I'm going to continue this experiment for the 3 months.

 

In Colorado higher octane isn't needed, there's no air! 85 octane here does the same as 87 octane at sea level.
I'm getting 15 1/2 - 16 using the cheaper gas. I actually improved my MPG by just closing all my windows and using the A/C.

 

Lee F. has it right.
I got to work on a problem truck awhile ago that would drop timing because of the knock sensors picking up "noise"
The PCM's are programed to only look for "noise" during certain time periods. It ignores valve events and combustion so when "noise" happens the PCM reacts very quickly and in most instances you will never know the timing was retarded.