I have had multiple emails with Coles over their diesel fuel prices in Geelong and South Geelong since February. Basically their sale price has been 150.9 cents per litre compared to other free fuel companies having prices between 134.9 and 146.6 cents over the same period. So even with the four cents a litre discount Coles diesel is more expensive. However the problem is worse than that. When Coles advertises greater discounts - “Choose 16 POINTS or 8 cents off per litre when you fill up at Shell Coles Express! (Excludes Diesel and LPG - refer below for terms and conditions)” - as noted diesel and LPG are excluded. It Coles has not been validly justify these exclusions in any way. Take a diesel in particular, for light vehicles diesel consumption is less than petrol consumption for the same kilometres so for these car owners the overall benefit of the discount is less than for petrol cars. So the overall financial benefit is less for diesel cars with the normal 4 cents a litre discount. Yet these vehicle drivers are excluded from the extra benefits. Pressure should be put on Coles to either justify this situation, or to change their exclusions!
When business makes such exclusions it is for their bottom line and at their discretion. It has been widely publicised Coles/Shell has had higher prices than any and all of the competitors because of the supply arrangements they signed to. They can set whatever rules they wish. For one aspect if ‘you’ need less diesel they have decided a higher margin suits their P/L, hence the exclusion.
Most of us just stopped buying Coles/Shell and moved on. Since it is a better deal elsewhere and you know it, are you tilting at windmills to get Coles/Shell to reduce prices to only a little above their competitors rather than many cents above? This competitive situation has been ongoing for some years now and nothing new.
Coles is apparently happy with their supply ‘deal’ as is since they just re-upped with them, although it might make little if any sense to us customers (and x-customers).
A post I did yesterday under Petrol Prices.
"26 DAYS LATER
Fred123
18h
Yesterday I noticed that all the servos including Coles Express that I drove past had U91 at 137.9 cents per litre on the price boards.
As we had a FlyBuys offer for 6 cents per litre discount, I grabbed a Coles fuel docket and went to the local Coles Express today after checking that all the prices were still 137.9 cents per litre, so I ended up paying 127.9 cents per litre.
Despite all the local rogues now fixing their prices to the same as United, there was no other vehicle at the bowsers when I pulled up although 2 others pulled up before I departed.
Perhaps Coles Express has finally woken up to the fact that having the highest prices in town does not generate much profit if no one is buying, but dropping their prices now is a bit like closing the barn door after the horse has bolted."
It appears that Coles have finally woken up, but it would seem like a case of Too little, too late.
Coles has an agreement with Viva Energy for the retailing of petrol at Coles. In February 2019, due to diabolically poor fuel sales at Coles Express, a new agreement was entered into try and make Coles more competitive in tbe market place. Information about this agreement is here:
I agree with @PhilT comments.
In addition to these, if Coles say was forced to discount all fuels at its Coles express, it could potentially set a precedent where anyone offering a product at a discount/on sale, they would be required to offer the same discount across all products they sell. This would mean that retailers could not offer specials on particular products anymore, and any discounts would need to be over all products. This would in effect end the days of discounting/products on sale.
Coles is usually still $0.04~0.05 above any of the other locals in Melbourne although on rare days they meet the competition for 91. Yet they still seem to have sufficient business; customers can be strange 
Hi all. I’m reporting on the Specials Coles offers. Happy to give extra discount on Petrol but not diesel or LPG
You are not the first, and I am not aware if this snipped exchange below was either. At that point in time Wesfarmers, with Coles and flybuys was one company so it possibly made sense it was directed to flybuys rather than Coles. It seems a comparatively long-standing point of irritation with Coles customers.
In addition they do not honour the discount for payments by Fleet Card, Shell Card, MotorCharge or MotorPass, in addition to excluding diesel and autogas but as I noted
A point was made that Coles has no obligation to include every fuel they sell, nor are they required to justify their business decisions to customers. One must assume the media staff approached marketing a year ago as they promised, and since nothing has changed they were rebuffed.
Customers not happy about Coles (or any businesses’) practices usually can and should vote with their feet and dollars.
You noted
but given the history of Coles pricing and supply agreements and exclusions, it is Coles’ conscious business decision to prioritise margin over market share as well as to exclude diesel and autogas and some payment types. It has been widely reported it has cost them business, and they are apparently accepting of that.
If you primarily shop at Coles for the discount I can understand why you feel diesel and autogas users are being discriminated against by not getting the discount. Why not spend a token amount at Woolies for their fuel voucher, or do they similarly discriminate?
It would be easy for most, and has been our previous strategy.
The one caveat here might be regional areas where the options are far more limited. There are enough examples that demonstrate all is not equal where the notion of loyalty and discounts offer little to someone who does not live in or near to a city.
One personal experience is of a community with only one servo. Shell! Need a discount, it is only 145km to Coles. The good news is you might drive past Coles on the way to Woolies. Fortunately you can fill up at the Woolies petrol nearby. All the better if you have a 200l long range fuel tank.
