Fuel brands and octanes [Poll included]

Skysurfer · Post by **Skysurfer** » Wed Jun 25, 2025 9:35 am

Hi folks,

I'm interested to know what everyone's opinions on fuel options are, personally, I only ever fill up at Shell or BP.

When I bought my Z4, the dealer took me to an Esso garage to fill up the tank. That rankled for a couple of weeks until I got to fill up at my local Shell.

I'd never really paid attention to the octane question and only ever opted for E10 but now I have a Z4 I'm not sure if I should be using E5 either a) all the time, b) occasionally, or c) ever.

The poll itself is to provide a visual representation, so I've made it multi-choice but please do let me us know your thoughts and opinions in the comments.

Edit to add: The Zed is my daily driver, if that makes any difference.

z4lincs · Post by **z4lincs** » Wed Jun 25, 2025 9:49 am

I'm almost exclusively using Tesco Momentum... can't face those BP prices

Usel · Post by **Usel** » Wed Jun 25, 2025 9:53 am

If I don't plan on using the Zed for more than a month I put in E5, Shell or Tesco.

When using the Zed I put anything in it.

tomscott · Post by **tomscott** » Wed Jun 25, 2025 9:59 am

Got to be honest these poles have been done to death and are pretty meaningless.

I was a shell officionado for years but then when prices soared I reevaluated.

Ive used Tesco 99 momentum because it is essentially the same stuff on the Esso forecourt.

Currently, Shell 99 Super is the same price in my area, so I've been using it again. Personally, I have felt no difference in my car so far roughly 5 tanks in.

Just a warm feeling from the marketing that its "better" for the car and will keep it cleaner.

My M has done less than 2500 miles in the last 2 years so my minimal milage doesn't worry me at all.

At the end of the day, all of the fuels meet British standards which is all most people need to know and that is why its there. No fuel is "Sh*t" and all modern cars are designed to run on everything we have. The UK has some of the best standards on fuel in the world so it really isnt a concern.

I ran a Mini Clubman JCW for 7 years on supermarket fuel, didn't matter what, just whatever was cheapest. I did 100k and didn't have a single issue.

At the end of the day for most the Z is a second or third car and milage vs ownership time is small so for most people it will make no difference what so ever.

Something to think about is that 97/99 sometimes sits a while. I filled up at my local Esso/tesco on 97 a couple of years back and the car ran like absolute rubbish. That garage obviously wasnt selling much and it had been sat for a while. Put some Super from another garage and it started behaving again.

I also prefer 99 if i have the option, BP I think only had 97 as their most premium fuel for a while. Might have changed.

caius · Post by **caius** » Wed Jun 25, 2025 10:09 am

The 2.5i I ran on anything I could get my hands on, running it on E5 vs E10 didn't make any noticeable difference. The 3.0si I've been putting E5 in where possible, but will also throw half a tank of E10 in if I can't get anywhere. Mostly Morrisons Premium which is E5 97 Octane.

I read somewhere around the time I got the 3.0si the fuel sensor on this generation doesn't adjust that quickly to mix changes, so its better to be consistent for a few tanks/miles than switch back & forth between the two. I've not run the 3.0si on E10 long enough to know if E5 is making a difference or not, I'm happy to just spend the money on it and enjoy the car.

buzyg · Post by **buzyg** » Wed Jun 25, 2025 10:32 am

Started as an avid Shell Super user. Ended mostly using Tesco Super. Tried pretty much all of them in between. There really ain't much difference in the real world.

tomscott · Post by **tomscott** » Wed Jun 25, 2025 10:40 am

caius wrote: Wed Jun 25, 2025 10:09 am I read somewhere around the time I got the 3.0si the fuel sensor on this generation doesn't adjust that quickly to mix changes, so its better to be consistent for a few tanks/miles than switch back & forth between the two. I've not run the 3.0si on E10 long enough to know if E5 is making a difference or not, I'm happy to just spend the money on it and enjoy the car.

It takes 2-3 tanks for it to adjust. Best to try and keep the same octane.

Boyo · Post by **Boyo** » Wed Jun 25, 2025 10:44 am

Tesco 99 Momentum every time including my lawn mower!

PerryGunn · Post by **PerryGunn** » Wed Jun 25, 2025 11:56 am

Distilled unicorn tears add at least 0.001 HP and give me an additional 30cm per gallon so I won't run the Alpina on anything else....

TIMMOS29 · Post by **TIMMOS29** » Wed Jun 25, 2025 12:04 pm

98 Unleaded

Pondrew · Post by **Pondrew** » Wed Jun 25, 2025 12:23 pm

Whatever is cheapest.

Petrol all comes from the same place in the UK and I seriously doubt that anyone (especially supermarkets who buy the vast majority) have a special 'recipe' for whatever gets poured into their forecourt tanks. Pays your money and take your choice.

Pondrew · Post by **Pondrew** » Wed Jun 25, 2025 12:25 pm

Skysurfer wrote: Wed Jun 25, 2025 9:35 am I'd never really paid attention to the octane question and only ever opted for E10 but now I have a Z4 I'm not sure if I should be using E5 either a) all the time, b) occasionally, or c) ever.

You do whatever makes you happy. The car won't give a shite.

PerryGunn · Post by **PerryGunn** » Wed Jun 25, 2025 12:56 pm

Pondrew wrote: Wed Jun 25, 2025 12:25 pm
Skysurfer wrote: Wed Jun 25, 2025 9:35 am I'd never really paid attention to the octane question and only ever opted for E10 but now I have a Z4 I'm not sure if I should be using E5 either a) all the time, b) occasionally, or c) ever.
You do whatever makes you happy. The car won't give a shite.

Cars won't mind but some other equipment does - I have a plate compactor that specifies that it needs Super Unleaded with no Exx marking as the Exx fuels contain Ethanol and the rubber parts can't tolerate Ethanol

If you're SORNing your car over winter, it's a good idea to brim fill with Super Unleaded with zero Ethanol. Ethanol is hygroscopic and absorbs water from the air (even with normal fuel, brim filling minimises the fuel/air interface area).

NB In long term storage, it's possible for the water content to reach the point where it separates from the fuel. The water will then sit at the bottom of the fuel tank, which is where the fuel pickup is, and we all know that engines don't burn a water/air mixture very well. Some people use fuel stabilisers but brim filling should negate the need other than for very long term storage.

Skysurfer · Post by **Skysurfer** » Wed Jun 25, 2025 1:39 pm

Is 0 ethanol the equivalent of aviation fuel?

Skysurfer · Post by **Skysurfer** » Wed Jun 25, 2025 2:23 pm

tomscott wrote: Wed Jun 25, 2025 9:59 am Got to be honest these poles have been done to death and are pretty meaningless.

Maybe so, but I'm not here trying to change anyone's opinions but my own. As it stands right now, there's a majority for Supermarket E5 (which at a guess is Tesco 99 Momentum), so my meter is moving already.

tomscott wrote: Wed Jun 25, 2025 9:59 am At the end of the day, all of the fuels meet British standards which is all most people need to know and that is why its there. No fuel is "Sh*t" and all modern cars are designed to run on everything we have. The UK has some of the best standards on fuel in the world so it really isnt a concern.

I hear you on this, but, if I'm not mistaken, there have been occasions where there has been contaminated fuel put out to the pumps that have caused massive issues. It happened to me once in a few years ago; my local Morrisons came under fire from a load of people because there was an issue with the fuel.

tomscott wrote: Wed Jun 25, 2025 9:59 am At the end of the day for most the Z is a second or third car and milage vs ownership time is small so for most people it will make no difference what so ever.

Yeah, I've updated my post to point out that this is my daily driver.

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