Preliminary gas brand vs emissions results for all to ponder

[fishbone79]

Here is some information that will interest you all. For the past 4 months I’ve been collecting this data. Given that I know the consistent and almost exact miles/gallon of fuel my EJ22 NA consumes around town (arithmetic mean 26.4M/G), I filled my gas tank at 9 different gas stations to a set number of gallons (Shell, Exxon, Mobile, KwikFill, Gulf, BP, Hess, Citgo, and Getty). Each tank was filled at different type of gas station (when available, the tanks were split between 2 stations of the same type, to alleviate any sampling error), and run almost dry before refilling at another type of gas station. I then used a particulate and volatile organic matter meter to determine the Volitile Organic Carbon (VOC) emissions of my engine, measured at the tailpipe. Measurements were taken both before and after long hard drives when the motor was hot. Cold motor measurements were disregarded because of the high levels of emissions during cold operation. Here are the results of the arithmetic means of the measurements:

Gas station Prior to drive, hot (PDH) (micrograms/liter)(u/L)--- After drive hot (ADH) (micrograms/liter)(u/L)

Station: PDH: ADH:
Hess 38 41
Shell 50 58
Getty 52 58
Mobile 62 97
Exxon 64 92
Gulf 87 92
Citgo 92 99
BP 103 104
Kwikfill 122 128

(stupid formatting)

It is important to not that VOC’s are indeed bad things to have in your exhaust, they basically mean unburnt fuel (but it is a bit more complicated than that, they are also organic byproducts of combustion and fuel additives like MTBE and etc, so they can not be directly related to any changes in fuel consumption in M/G, believe me, I tried like hell to make it work, but it wont). All these measurements were taken from 87 octane fuel. My interpretation is this: The cleanest and most entirely consumed gasoline is Hess, and the crapiest (that I tested) was Kwikfill. I believe the numbers can be interpreted to mean the amount of crapola the gasoline you choose leaves in your motor. Thus, high carbon buildups (in ones motor) and emissions, as well as clogged Catalytic converters are a function of the brand of fuel you burn.

However, it should also be noted the significant difference between the pre and post drive measurements for mobile and Exxon gasoline. It has long been questioned whether or not Exxon/Mobile add detergents to their gas; well, it think the numbers speak for themselves, yes! It makes sense that after a hard run your motor will be blowing out more shit if the gas contains detergents because there was more volumetric contact between engine internals and gasoline. However, these numbers may also be a result of using Exxon/Mobile fuels right after burning BP fuels (which I did). This may mean the crappy BP buildups were being stripped by the mobile gasoline, but may intern support the postulate that these gasolines contain detergents. Ironically though, Hess was the last gasoline I tested, after KwikFill, and it was the cleanest… Does this mean Hess is cleaner, or that it contains very few detergents? More detail is necessary, and more data needs to be collected, but I thought you might all enjoy my preliminary results.

It is also realized that my miles/gallon rating wavers a bit with the type of gas I use, but is fairly constant. The difference in M/G was recorded for each gasoline, but has not been reported here because I have no idea what the fuck it means… lets just say its not what I expected.

Cheers,

Morgan

[vrg3]

I'm still digesting your writeup... Seems very interesting though.

Quick note -- you can get better formatting if you use the [code] [/code] tags.

[THAWA]

that's awesome but what the hell is Hess? Looks like I may have to get a shell card

[vrg3]

Did you have your oxygen sensor hooked up during these tests, Morgan? I feel like the numbers would have more validity if you ran without the oxygen sensor's feedback (and reset the ECU)... That way the same amount of fuel would be injected regardless of the type of fuel and how completely it combusted.

[fishbone79]

Yeah, I had my O2 sensor unplugged the whole time. It usually runs the same regardless of whether or not its hooked up (and it does work, I tested it). I should add that I am interested in what others think these numbers might mean.... always good to have different points of view.

Cheers!

Morgan