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## tcpdump

311 posts

Ultimate Geek

Topic # 113157 8-Jan-2013 13:34

Hi,

I was curious about the optimal use of the AA card for fuel savings at Caltex.
The following table takes assumes \$2.10/L and a 6c/\$40 discount accumulated (being an AA member):

- 19.04L x \$2.10 = \$40
- 50L x \$1.98 = \$99
total - \$139 for \$69.04L -> 2.01/L

- 38.08L x \$2.10 = \$79.96
- 50L x \$1.92 = \$96
total - \$175.96 for \$88.08l -> 1.99/L

- 76.16L x \$2.10 = \$159.93
- 50L x \$1.8 = \$90
total - \$249 for 126.16L -> 1.97/L

- 190L x \$2.10 = \$399
- 50L x \$1.44 = \$72
total - \$471 for 240L -> 1.96/L

- 380L x \$2.10 = \$799.68
- 50L x \$0.84 = \$42
total \$841.68 pt. 430L -> 1.95/L

- 647L x \$2.10 = \$1359
- 50L x \$0 = \$0
total \$1359 for 697L -> 1.94/L

It seems that the 50L limit is intentionally set so low (compared to the 150L on supermarket vouchers).

Conclusion? The easiest way is to put \$40 worth of fuel and then put 50 more liters  (assuming you have a large enough tank) which is the way I've been doing it.

It is slightly more economical to put a few more \$40 but it may not worth the hassle and the points do expire after the end of the second month if I recall correctly.

Hope this helps someone.

Cheers

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## Behodar

5921 posts

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Can you clarify what the second line of each calculation means? I'm not sure where these \$1.98, \$1.92, etc. prices are coming from.

I've just filled up (my tank holds less than 50 L) with an 8c discount so that's a total of \$1.989/L. Not the best price but I guess it'll do.

## tcpdump

311 posts

Ultimate Geek

Hi,
The second line indicates the actual price paid for every liter of the discounted 50L.
The first example (\$1.98/L) is made out the full price (\$2.10 in my example) minus \$0.12 discounted (6c for the \$40 filled plus the 6c that you automatically get even when redeeming).

The second example (\$1.92/L) is made out of the \$2.10 minus \$0.18 (twice \$40 means 12c/l plus 6c/l you get when redeeming).

Cheers.

## scuwp

2765 posts

Uber Geek

Doesn't the discount come off the 'first' 40 litres? You sound as if you buy 40 litres, and then go back and in a separate purchase fill up the rest of the tank. Seems a lot of work for a few cents savings if that's the case. I don't think it work like that.

Personally I just fill the tank and hand the card over, sometimes I save enough to buy a packet of chewing gum, other times maybe a packet of jaffa's.

Always be yourself, unless you can be Batman, then always be the Batman

## sbiddle

25668 posts

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Biddle Corp
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tcpdump: Hi,
The second line indicates the actual price paid for every liter of the discounted 50L.
The first example (\$1.98/L) is made out the full price (\$2.10 in my example) minus \$0.12 discounted (6c for the \$40 filled plus the 6c that you automatically get even when redeeming).

The second example (\$1.92/L) is made out of the \$2.10 minus \$0.18 (twice \$40 means 12c/l plus 6c/l you get when redeeming).

Cheers.

You don't get 6c + 6c off when redeeming. You get 6c off with a minimum purchase of \$40 - it doesn't matter if you spend \$40 or \$80, you still only get 6c per litlre off.

I actually don't understand your logic or math.

## kingjj

Baby Get Shaky!
1494 posts

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My local Caltex advised me to pump \$40 worth, hang up the bowser, remove the bowser and pump another \$40 (repeating as necessary). All this would be in same transaction, but he claimed that it could be treated as several transactions so could be charged as such (ergo each \$40 pump would accumulate a 6c discount). I have not tested this theory but he seemed matter of fact about it.

## sbiddle

25668 posts

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kingjj: My local Caltex advised me to pump \$40 worth, hang up the bowser, remove the bowser and pump another \$40 (repeating as necessary). All this would be in same transaction, but he claimed that it could be treated as several transactions so could be charged as such (ergo each \$40 pump would accumulate a 6c discount). I have not tested this theory but he seemed matter of fact about it.

That's fine if you need over 50L, but the vast majority of people don't.

6c per litre of \$40 + 6c per litre off another \$40 is the same discount as 6c per litre off a single \$80 fill.

I'm guessing that some of you are mistaken into thinking this equates to a 12c total discount?

## logo

268 posts

Ultimate Geek

sbiddle:
tcpdump: Hi,
The second line indicates the actual price paid for every liter of the discounted 50L.
The first example (\$1.98/L) is made out the full price (\$2.10 in my example) minus \$0.12 discounted (6c for the \$40 filled plus the 6c that you automatically get even when redeeming).

The second example (\$1.92/L) is made out of the \$2.10 minus \$0.18 (twice \$40 means 12c/l plus 6c/l you get when redeeming).

Cheers.

You don't get 6c + 6c off when redeeming. You get 6c off with a minimum purchase of \$40 - it doesn't matter if you spend \$40 or \$80, you still only get 6c per litlre off.

I actually don't understand your logic or math.

It's all to do with buying the minimum of fuel and accumulating the discount and once you have a big discount then doing a big fill.

e.g. (to make the maths easier, assume petrol is a round \$2 per litre).

Fill 1 - \$40 (20 litres) - accumulate 6c discount
Fill 2 - \$40 (20 litres) - accumulate 6c discount  (total now 12c)
Fill 3 - \$40 (20 litres) - accumulate 6c discount  (total now 18c)
Fill 4 - \$40 (20 litres) - accumulate 6c discount  (total now 24c)
Fill 5 - \$40 (20 litres) - accumulate 6c discount  (total now 32c)
Fill 6 - Fill up with 50 litres and redeem 40c discount (32c accumulate + 6c)  (total cost would be \$84 to fill)

Total spent = \$284 for 150 litres = \$1.89 per litre - an average discount of 11c per litre which is 5c per litre more than if you just took the 6c discount.

Points to note:
- The longer you can accumulate the bigger the average discount. If you stop at fill 2 then you aren't making any additional saving
- You are paying full price for the fills leading up to the big final fill
- The discounts start expiring at the end of the next calendar month which limits how much many fills you can make
- The discount applies to a maximum 50 litres.

I've done it myself as an excercise and it's not worth the extra stops to put in just \$40 of fuel. I usually wait until the light comes on and then fill up the tank so for me that's 3 times the number of visits to a service station. How much is my time worth? I also don't use that much (I bike or run to work) so found that I wasn't accumulating the discounts fast enough.

## sbiddle

25668 posts

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For for all that effort all you actually end up doing is saving \$1.20 on a big fill because you've accumulated 6c discounts across 5 visits and can add on the 6c AA discount when you redeem... Hardly seems worth it.

## lurker

620 posts

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I tank \$40 each time, and save the discounts, and then cash in at the end of two months. That typically gets me close to \$2 off a litre, so \$100 or so.

You can do multiple \$40 fills in the same visit, provided you can also then convince the attendant to put them through as separate transactions. That way you'd get 12 or 18 cents off. If you're really desperate you can do two \$40 fills on one pump, and reach around and do a single \$40 on another.

Also, sometimes BP have a "Thirsty Thursdays" where it's 8 cents.

It's ok if you're near a BP as I am, I just keep popping in every 2-3 days for another \$40.

## logo

268 posts

Ultimate Geek

lurker:
You can do multiple \$40 fills in the same visit, provided you can also then convince the attendant to put them through as separate transactions. That way you'd get 12 or 18 cents off. If you're really desperate you can do two \$40 fills on one pump, and reach around and do a single \$40 on another.

Doesn't quite work out to be economical - again using the \$2 per litre price for simplicity:

Fill 1: \$40 (20 litres) - no discount - 6c accumulated
Fill 2: \$40 - 12c discount = \$37.60

Total cost is \$77.60 for 40 litres = \$1.94 per litre or 6c discount. No different than if you just filled up 40 litres at 6c off

You will get a very small benefit if you manage to get a third fill in but not worth the effort

The times when this does work is if you accumulate both fills 1 & 2. That way each visit you accumulate 12c and make less visits so instead of say 8 visits you only really do 4 (with double fills each time)

## logo

268 posts

Ultimate Geek

sbiddle: For for all that effort all you actually end up doing is saving \$1.20 on a big fill because you've accumulated 6c discounts across 5 visits and can add on the 6c AA discount when you redeem... Hardly seems worth it.

In my example it works out to be a \$7 saving (\$291 total spend if you took the 6c discount everytime vs \$284 if you accumulated)

That's over 6 fills - I think you you extrapolate it out over a few more fills the savings will increase but it hits a maximum at around the 7-8 fill mark (of around 13c a litre) due to the 50 litre maximum discount limit.

Anyone care to put that into a formula or something and prove it mathematically?

## lurker

620 posts

Ultimate Geek

Subscriber

Sorry, I might not have been clear with my previous post. I accumulate everything so when I say 12-18 cents off I mean I'm banking those savings, not using them on the current fill.

For me, the way this all works is like this:

I used to tank once weekly (\$120+) getting the 6 cents for the first \$40, effectively \$2.40 a week saved. (That was when I didn't really know what it was about). After two months I'd probably saved about \$20 or more in my total savings.

Now I fill \$40 every time, getting 18 cents a week and by the end of 2 months I'm over \$1.40.
Then I also fill my wife's car (though that accounts for far less), I also get a few cents from TCL and other places etc. I wish I could have a gas bottle to fill, I think it's 40 or 50 cents in one hit. I really must drag the BBQ out of the shed and burn some meat.

So for me, it's definitely beneficial doing it in \$40 chunks.

## logo

268 posts

Ultimate Geek

lurker: Sorry, I might not have been clear with my previous post. I accumulate everything so when I say 12-18 cents off I mean I'm banking those savings, not using them on the current fill.

For me, the way this all works is like this:

I used to tank once weekly (\$120+) getting the 6 cents for the first \$40, effectively \$2.40 a week saved. (That was when I didn't really know what it was about). After two months I'd probably saved about \$20 or more in my total savings.

Now I fill \$40 every time, getting 18 cents a week and by the end of 2 months I'm over \$1.40.
Then I also fill my wife's car (though that accounts for far less), I also get a few cents from TCL and other places etc. I wish I could have a gas bottle to fill, I think it's 40 or 50 cents in one hit. I really must drag the BBQ out of the shed and burn some meat.

So for me, it's definitely beneficial doing it in \$40 chunks.

You would get 6c off a litre for the entire fill (up to 50 litres) when you were filling up once a week. That means a maximum discount of \$3 (50 x 6c)

With the \$40 topups you may end up accumulating \$1.40 in discounts however that \$1.40 is only applicable to a maximum of 50 litres in your final fill. In the meantime, you've paid full price for the previous fill ups. Up to a point there is some benefit - although it will be under \$10 - but beyond that you end up paying more in full price petrol than what you gain from a big discount from one 50 litre fill further down the track.

I had whipped up a spreadsheet a while back which calculated the optimum number of topups to get the maximum benefit but can't seem to find it anymore. I remember being disappointed with the actual savings when taking into account the extra number of fills one had to do.

## lucky015

629 posts

Ultimate Geek

Although it is a fairly decent system it is only slightly more effective than picking your gas station wisely which allows you to buy as much as you want as often as you want.

## lurker

620 posts

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Subscriber

Ah, yes my logic on the full tank fill is off. So if I get the 6 cents off the first 50 litres for a full tank then it's \$3 indeed, but over 8 weeks that means I've saved \$24 right? At the end of the two months, if I only had accumulated 48 cents I'd save that on the 50 litre fill. But just my car alone, I can almost triple that. Maybe my maths is off, I might have to knock up a spreadsheet to see how it really stacks up for me.

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