What I presume was a table has been completely lost, but I did the calcs once and figured out that there was no benefit. The only time I accumulate is when someone else is paying :)

Money now, is worth more than money later. Simple as that.

Why? Various reasons, but for one, think of inflation.

Behodar:

 

What I presume was a table has been completely lost, but I did the calcs once and figured out that there was no benefit. The only time I accumulate is when someone else is paying :)

 

yip saw that as soon as I posted

If you do a $40 fill followed by a complete fill then it does save you *something*

Let's say petrol is $2 a litre to make calculation simple, the actual price isn't far off this (maybe $1.80 on average, at least in most of Auckland)

$40 spent, no discount = $40, for 20 litres, 6c accumulated

Next time you fill up from empty - let's say 45 litres = $90

But with your 6c accumulated discount and 6c new discount (a total of 12c/litre) that is $90 - 45 * .12 = $84.60

Your total spend for 65 litres is $124.60 because you accumulated

Now if you'd used the discount.. the first 20 litres would cost you $40 - 20 * .06 = $38.8 and your second fill = $87.30 for a total of $126.10 without accumulating

So by accumulating on your $40 fill you saved $1.50

OP your math doesn't make much sense, why have you added up the $/L ? And in your scenario you always do a $40 fill, which doesn't do anything for you.

ubergeeknz:

 

If you do a $40 fill followed by a complete fill then it does save you *something*

 

Let's say petrol is $2 a litre to make calculation simple, the actual price isn't far off this (maybe $1.80 on average, at least in most of Auckland)

 

$40 spent, no discount = $40, for 20 litres, 6c accumulated

 

Next time you fill up from empty - let's say 45 litres = $90

 

But with your 6c accumulated discount and 6c new discount (a total of 12c/litre) that is $90 - 45 * .12 = $84.60

 

Your total spend for 65 litres is $124.60 because you accumulated

 

Now if you'd used the discount.. the first 20 litres would cost you $40 - 20 * .06 = $38.8 and your second fill = $87.30 for a total of $126.10 without accumulating

 

So by accumulating on your $40 fill you saved $1.50

 

OP your math doesn't make much sense, why have you added up the $/L ? And in your scenario you always do a $40 fill, which doesn't do anything for you.

 

The benefit of accumulating is so small

ubergeeknz:

 

OP your math doesn't make much sense, why have you added up the $/L ? And in your scenario you always do a $40 fill, which doesn't do anything for you.

 

Seriously? Total spent...

One minimum fill with an accumulate followed by the largest fill you can do is the only scenario where it works.  You're right though, the benefit is small.  Where you get the real benefit is accumulating discounts from things other than fuel.

dryburn:

 

 

 

ubergeeknz:

 

OP your math doesn't make much sense, why have you added up the $/L ? And in your scenario you always do a $40 fill, which doesn't do anything for you.

 

 

Seriously? Total spent...

 

Summing this column ($/L) doesn't make sense, it would make more sense to average it.

ubergeeknz:

 

dryburn:

 

 

 

ubergeeknz:

 

OP your math doesn't make much sense, why have you added up the $/L ? And in your scenario you always do a $40 fill, which doesn't do anything for you.

 

 

Seriously? Total spent...

 

 

Summing this column ($/L) doesn't make sense, it would make more sense to average it.

 

I see your point. My mistake.

To minimize your payments to BP/Caltex, you should keep accumulating points with $40 fills until you’re about to run out of your 2 month accumulation window. Then get a 50L fill. At $1.919/L, $40 ~= 21L. Each time you accumulate, you get 50L (i.e. a bit more than twice as much) petrol at the discounted price... i.e. a bit more than twice the discount you would have got if you'd cashed in.

Here’s a spreadsheet to show how it works out. You can adjust the discount and petrol price at B2 and D2. Basically, the higher the price, the better it is to accumulate.

NB:

 

1. Try to cash in with your 50L fill before any petrol price rises.
2. Don't ever put in more than 50L -- the excess is all undiscounted petrol. Similarly, don't ever put in less than $40.
3. Waze is an Android app which uses crowd-sourcing to allow you to see petrol prices (as well as doing all the usual routing, etc).
4. At the current price ($1.919c/L) and standard (6c/L) and you fill up 8 times/2 months, if you see (e.g.) Waitomo selling at $1.79 or less, you're better off filling up completely there.
5. The periodic 10c/L discounts screw up the above calculations. If you could get all fills at that discount, it moves your Waitomo decision point to $1.71.
6. If you value your time, then you're probably better off to just fill up totally every time.

Thanks for the detailed answer. 

I can't access your spreadsheet

dryburn:

 

 

 

 

 

 

Am I calculating correctly? There is absolutely no benefit to accumulating the cents/litre

 

I accumulate when out of Wellington (because anywhere north of here is basically cheaper) and redeem when back in town :)

I accumulate each time i go to BP, Every week they seem to have a day of 10 cents of.

I always do the minimum of $40 for the discount.

Car hold 65L, so can do two lots of $40 on the one pump, and pay separately.

Then you get 10 cent of each transaction.

You can do 3 fills per pump before going in to pay.

You benefit on accum by only buying $40 gas (or using two pumps at $40 each if you need to fill up) and then redeeming on a full tank.

Smartfuel is just a scam. The sooner it's outlawed by the Commerce Commission the better off we'll all be (such schemes have been banned by the ACCC for a few years now)