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Help Me Establish Gas Station Fraud- By Exposing Fuel Manipulation. Answered

Prelude:Every week I only ever travel the same route, at the same time, with the same amount of traffic on the road.

I fill my cars fuel tank once a week, with $50AU of petrol.
The prices lately have been stable and around $1.30AU/L

What this post is about is the fact that due to me travelling the exact same Km's per week, I have noticed a significant difference between the two petrol stations fuel that I fill at.

Can anyone educate me as to why when I fill at one station I get 8 days of travel and when I fill at the other station I only get 4 days of travel?

Once again I am filling the same amount of fuel at each station, just one stations fuel (Major corporate outlet) seems to be of a much lower quality.

Is it possible that something is a-miss with this situation. Is there a variable im not considering?

After 4 months of weekly refills I feel that conclusively, one stations fuel seems to combust better than the others.

Is this possible and if so are there any home experiments I could try to prove my theory via testing the fuels combustion/quality.

I only write this as I sit here on a week, where I was forced to fill up at the "suspect" station. Im on day 3 now and my fuel is red lining... What is happening?

I know the difference of 3 -8 days is a massive, surely others would have noticed this also. I thought I was mistaken the first few times it happened. But now I am positive, something is wrong.

I might add, I use premium fuel with the same octane level at both stations.
Could that be it? Would they be mis-quoting the octane level in their fuel? That is the only thing I can think of.


Another thought, get a small amount of each fuel and do the coffee bean test, it's not perfectly accurate but it would show up if there's a major difference in energy density, a beaker with a litre of water and an exactly measured amount of each fuel, you check the temperature of the water before and after burning. There's an 'ible on it about burning sweets, the process is essentially the same, if there's a significant difference in temperature change then it's lesser quality fuel that's the problem.

Thats what I was thinking!! A simple burn test... Exactly what I was after. I knew that was an obvious solution. I shall aquire some fuel and try it. Thanks.

Another good test could be to fill a jerrycan with with the pump says is, say, exactly 1 gallon at each station, take them home and measure precisely. As for the burn test, coke cans make great containers for holding the water you are heating because they are light so don't absorb much heat, and have concave bottoms to catch the most heat from the flame. (Even in a GCSE chemistry practical with all the lab glassware we wanted we used coke cans)

Well if the station has larger reservoirs or less traffic - maybe both it'll have lesser quality petrol as it goes off though you'd need to have it turning to paint stripper before it's an issue.

As nacho said a mis-calibrated meter is another suspect, big name stations mean worker bees, people that work there often don't give a rat's ass about the place.

Of course that could give way to there being water in the tanks from seepage etc. also it could be to do with the type of petrol it is - though standardized some cars just hate a certain petrol, is it a fairly high strung machine?

For testing the meter theory take a jerry can and fill exactly to a certain level on the can - compare pump readings.

I've worked for a high staff level business for 7 years. I know exactly what you mean. The casuals dont really care about the place in general.

. A friend of mine says it may be the meter in the pump. Either a worn meter or an unscrupulous dealer who has miscalibrated it.

Yes I have to agree if it was a no-name gas n go, yet it is a major service station chain..

DO you pump it till it shuts off, or just pump a dollar (or gallon/liter) amount?

It may be the meter. That would make sense.

Seems to be all their bowsers though.

I can't speak for Australia, but the meters here have to tested and sealed by the government, and when they are are repaired and the seals get cut they have to be proved (( using a calibrated test vessel with temperature compensation to be with in 5mL per 20 Liters for a low speed pump and with in 50 mL per 500 Liters in the high speed pump , refineries / bulk transfer stations typically use mass meter and they have totally different rules )) by the repair company, not the retailer and the repair company has to submit the results to the government department responsible for weights and measures... And the government will come out and do random checks to make sure retailers are being honest (( and there is talks about them proving meters on a bi - annual or even a annual basis )) and if the repair company abuses there trust there ability to prove meters is removed and this effectively hampers there ability to make a profit.... (( meter proving has huge profit margins )) Most large branded stations like Exxon, etc will also prove there own meters as part of there environmental monitoring to make sure they don't have an underground leak... (( Oh and they don't like giving away free fuel either )) Now filling at two different stations, there is lots of different grades of fuel, and it's not just regular and super, if one has ethanol blended into it you will get less energy per liter so you need to use more and they don't have to notify you of this so long as the octane level is correct for your area like 87 for reg and 91 + for super / premium and this is easy to obtain even with 15 % ethanol blended right in , one station may have temperature compensation, and one may not and depending on the temperature of your fuel the savings can be huge (( I have bought fuel from several station and I can't use it in my catalytic heater with out pre heating it but other stations I can )) It is also very hard to prove a meter by using a car and a gas gauge, because there is to many things that can change your fuel usage, like was it windy, was it warmer / cooler, was it raining, did you open the windows or turn on the A/C, was it day time or night time (( yes even turning on the lights will burn slightly more fuel..)) But to answer your question, there is not a lot you can do from home, however you can contact your governments department that is responsible for weights and measures and notify them of a problem, normally it only takes one or two complaints, and they will come out and do the testing, and if it's a major name brand station contact the head office and they will also investigate this because one thing every oil company has a problem with, is station owner that rips them off ... ((( They will let lots of thing slide but not this )))

I don't know about in AU, but here in the US, you can call the depatment of weights & measures to check out any shady things like this.

. Do you get gas at the suspect station only when the tank is empty? You may have water in your tank that is getting picked up when the tank gets close to empty. Just thinking out loud.

. A difference of 100% does seem like somebody else would have noticed. . Wild guess is that one of the stations has some old gas. Or maybe a hole in an underground tank and you're paying for a gasoline/water mix. . IIRC, octane doesn't make much (if any) difference in kM/L, unless it's too low and you get pre-ignition. Have you noticed any knocking/pinging on hard acceleration?

I notice that my car does not preform optimally when I refill at the suspect station. It actually conked out once (had the car 5 years and it has never stalls the engine) directly after refilling at that station. But it started up again very roughly straight away... I will most certainly try the settle technique to check for water.

. You should be able to find fuel filters, with clear bodies that you can insert in a "rubber" gas line that will trap water, at most auto parts stores. You will be able to see the collected water and it protects the carb/injectors. Probably won't work if your fuel pump is in the tank (pressure too high). . They don't allow gas through when wet, so keep a spare (or two) in the glovebox.

. Until you figure it out, I'd only buy enough gas at the suspect station to get me to the other one.

Yes that is what I have been doing. But this week (silly me) I thought "nah I'm just being stupid it is just some mistake" and filled up there again... Same thing this week. Ran out of fuel before the weeks end... It just seems so massive a difference. I can't see how it could be possibly. But time and time again it keeps happening... I am just curious now as to why... I'm going to ask the owner of the family service station why I get more km's out of there petrol. Maybe he has some ideas..

Yeah, I've seen the water/gas mixture. *fuming* >(

Is it possible that someone is siphoning it from your car? 100% is huge!

No, the car is locked up in my garage.

. Oh! How to test at home. . I don't know of any way to do DIY tests for octane and BTU content. BTU will probably be the most valuable test. You may be able to rig something up to get some relative results (eg, how far a gas/air cannon will shoot a golf ball). . Not sure how much water it would take to cause a 50% reduction in kM/L, but I'd think it would be enough to be visible to the naked eye. Look for cloudiness when it comes out of the pump. Allow to sit for a few hours (days?) and the water should settle to the bottom. A centrifuge will hasten the process. . You can check for dirt and non-volatiles by letting some evaporate in a petri dish or similar. In a well-ventilated area, of course.