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Hi all,

I've noticed that different petrol (similiar grade) caused the fuel guage to have different fuel consumption pattern. For example,

1) Shell 95; fuel level dropped fastest between 1/2 and 1/4 mark. Earlier from Full to 1/2 mark the drop is rather slowly.
2) Mobil 95; fuel level dropped fastest between 3/4 and 1/2 mark. Later the drop will be more gradual and evenly.
3) SPC 95; the level drop fastest around 1/2 mark, the rest rather constantly.
4) Caltex...have not tried it yet.

Although I've experienced different fuel consumption pattern as witness from the fuel guage, but overall fuel consumption among the various brand is almost the same, minimal difference. Meaning; a full tank of Shell, or Mobil or SPC will given me around the same mileage travelled until the fuel guage empty light comes on.

This difference in fuel consumption pattern (as observed from fuel guage) is repeatable, meaning its not a one time observation, whenever I use that particular brand the pattern appear again. Also travelling distance, timing and route is same, but its just that different petrol brand caused the fuel guage to give different reading (or different consumption rate?). Its not about the fuel tank profile/shape either, otherwise different brand will still give the same FC pattern, right?

I've check with one of my colleague, and he had observed the same findings...

So, just curious, have you noticed any difference in your fuel guage consumption reading when using different brand?

I had never compared, but on my previous ride, Shell 98 always drop the fastest between 1/2 to 1/4 mark, then slow down before the light up.

Hummm.... Interesting that when using Shell, your FC pattern is same as what I've observed...

Normally I judge on Mileage.......Not Fuel guage......

Yes, I understand actual mileage is what matter.

But my point is, how come different petrol will give different FC pattern? I support the theory that all petrol grade are the same among the different brand, they give similiar performance and mileage. But how come our fuel guage read them differently?

For example, noticed that Shell will hold out longer in the begining, and drop rather rapidly after 1/2 mark, could this be purposely 'designed/created' to give drivers the impression that it gives more mileage?

Ha ha, I thought I was the only one experiencing such things even though my traveling pattern is more or less fixed.

Mine is even weirder. I have always been pumping Shell 98 (always pump full tank) and my first quarter tank will last around 80km, 1/2 tank will be around 170-180km and then by the time the light turns on, I would have travelled around 420km. My rationale was that as the amt of petrol decreases, FC improves due to lighter load (less petrol).

Then I switched to Shell 95 (on my 2nd tank now) and I noticed for the first 1/4 tank, I travelled only 40-50km and by 1/2 tank, only 150km. But at the end, I will still hit slightly less than 420km when the light turns on.

Funny right? Same brand of petrol somemore. Only grade is different.

These may all be valid observations BUT:

1. How repeatable is the phenomenon? Have you all done 10 tanksfuls of each before coming to this conclusion
2. Have you always filled every tank yourself using the SAME PUMP and NOZZLE - these may stop at exactly the same level as calibrations are different. Do you also fill at the same time every time - this affects the vapour pressure and when the pump senses a full tank.
3. Have you ensured that your driving pattern and passenger load pattern is very similar on every tank?
4. Do you always read the tank gauges at exactly the same time - e.g. after being parked on a level surface for some time. Whilst driving, depending on whether you are going uphill or downhill, accelerating or decelerating, turning left or right, gauges move up and down.

There are too many variations above to come to any meaningful conclusion about whether different brands affect fuel gauge behaviour and my observations after driving for 16 years in Singapore with 6 different cars a total of over 250,000km and having kept detailed records for the past 15 years (on the mileage between markings on tank gauges - I can show you my records) is that:

THERE IS NO DIFFERENCE in gauge behaviour - FC, small diff 5% max, gauge behaviour, NO DIFFERENCE, NO DIFFERENCE!!

I don't think any one of you can show the sort of records I have !!

Yes, I've tried it for more than 10 tank full, even switched back and forth among the 3 different brands numerous times, and the pattern is repeatable.

As for whether I fill every trank myself or same pump or same nozzle or timing is no concern, because I'm not telling different petrol give different FC. But rather, different fuel the consumption rate (or rather, the fuel guage reading) is different, but overall consumption is around the same, its just that the fuel guage reading depending on the type of petrol, some seems to decrease earlier faster and some decrease later faster...

As I've stated earlier, most of my driving is to and back from work, >95% traveling the same route, same timing and alone.

Reading I noted while traveling on flat portion of expressway, not upslope nor downslope.

As for record, I've been keeping record for every petrol top-up since January 2004 till now, but like I've mentioned earlier, its not the total FC different petrol gives, but different fuel consumption pattern, as witness from the fuel guage. Please read one more time my first question carefully!

If you would, perhaps can try out different brand, and see if you can notice any different pattern in the rate of petrol decrease from your fuel guage. Overall mileage from different brand should be around the same, its just the rate of decrease among various petrol brand give different pattern....

i go by consumption.. not gauge behaviour.. but ur poll snooked me

I understand the actual FC is what matter, but I just don't understand why different brand can affect the fuel guage differently. According to the poll now, a few person have observed this phenomenon...

I understand your post fully, it is NOT about FC per se but about the rate at which the gauge goes down at different points. Read MY post carefully too.

I still maintain that from FULL tank to the first mark varies the most because of different fullness depending on actual pump and nozzle.

When I mean 10 tankfuls, I meant 10 of each grade of each brand, i.e. you have done about 100 tankfulls for the 3 brands in total.

I also maintain that fuel gauge readings are NOT reliable ON THE MOVE, in my experience. You need to be stationary for say 1 hour at the SAME temperature. E.g. I am exactly at 3/4 tank one day on the ECP going West on a flat straight stretch. 20 km later I can be above the 3/4 tank on the same straight stretch because I just changed lanes from right to left and gauge moves up from just below 3/4 to just above 3/4 about 1 km later.....

My views remain unchanged (of course you are welcome to disagree with me and vice versa - after all this is a forum.)

Edited by Russ, 21 February 2007 - 05:19 PM.

Its ok, I respect your reply.

Let's see what other have to say. I'm just curious by what I've observed, that's all.

I actually don't realy care about this weird guage thing but it's just something I notice on my ride also. So I am not alone.

Only using Shell as this is the only one near my place. Switching back to Shell 98 for my next tank. I feel that it gives the car more power than Shell 95. Price diff for full tank is around $3.

well, i don't pump enough of the various brands. i pumped enough to know the mileage difference but not enough to see the difference in fuel gauge behaviour. i have a fav brand and i stick to tt

Yes, I understand actual mileage is what matter.

But my point is, how come different petrol will give different FC pattern? I support the theory that all petrol grade are the same among the different brand, they give similiar performance and mileage. But how come our fuel guage read them differently?

For example, noticed that Shell will hold out longer in the begining, and drop rather rapidly after 1/2 mark, could this be purposely 'designed/created' to give drivers the impression that it gives more mileage?

Interesting to know quite a few people have noticed different brand of petrol affect the fuel guage differently...... Perhaps not all petrol are created the same, different brand have slightly different characteristic, and hence the unique reading from the guage?

Hi bro,

I noticed that too, I've used shee 95 and Esso 5000, it dropped very fast after 1/2 tank, and now i switch to Shell 98, it didn't drop so fast and FC has improved from 12.5km/l to 14.5km/l.

Techron Silver drops very fast on my Aveo but FC in the end still the same. I got 17km/L.

Hi Genie,

Wow, that's very good FC you've got.

Any idea how come such strange reading from the fuel guage?