Fuels

[mcleansc]

I want a 98RON Map and there are only 97RON (BP Ultimate and Esso Super Unleaded) near me. There is a Tesco close to me with 99RON Momentum. I'm always a bit wary of Supermarket fuels but since the Octane rating of a fuel is its anti knock properties should the Tesco stuff be better than the BP Ultimate? It's to go in my 335i so I'm a bit wary of det'ing the engine ('power' and fuel consumption don't bother me, just stability). I know there's a lot of smart guys on here who can put my mind at ease. Cheers

[zeppelin101]

Honestly? It will make little to no difference, especially if whoever is doing the map isn't determined to run it on the ragged edge.

Even though they have different names on the pumps, most of the fuels come out of a small handful of refineries and the base fuel stock is very similar, it's mostly different additive packs for cleaning agents etc that vary between pumps.

In point of fact, the RON rating is a minimum - so 95 is usually closer to 96/97 most of the time and 98 is around 99. With ethanol content going up in the base stock fuel RONs are almost always over achieving by a good amount, and will be higher than the advertised minimum by around 1 octane to avoid falling foul of a random sample test.

And unless it's being disabled (!), your car will have a functioning knock calibration which will take care of ignition on lower RON fuels.

[Actual_Ben_Taylor]

Tesco stuff is fine, better than BP Ultimate in my experience.

[mcleansc]

Thanks guys you've put my mind at ease. The fact that it's almost 10p a litre cheaper is also good ha.

I tried googling it but it was all fuel economy and how the car 'felt', not people tuning.

For the time being it's a staged map similar to the H-Dev ones, and I knew people reported their cars running a bit shit on 95 on a H-Dev generic tune so wanted to play it safe. I'll map for 98 and run the 99 Momentum. Thanks again!

[jbsauce]

they reckon turbo cars run better on Tesco because it has more ethanol in it, which increases combustion temp. probably internet/pub bullssshit lol

[sideways14a]

BP ultimate was chav p1ss when i put it in the sx way way back.. dunno if its improved - the 5 doesnt seem to care one way or other.

[Chriscooke]

My knock used to go through the roof on bp

[mcleansc]

My knock used to go through the roof on bp

BP ultimate was chav p1ss when i put it in the sx way way back.. dunno if its improved - the 5 doesnt seem to care one way or other.

Yeah I did see a lot of negative comments with regards to BP when I was searching the interwebs before coming on here. Doubt I'll be using that again.

they reckon turbo cars run better on Tesco because it has more ethanol in it, which increases combustion temp. probably internet/pub bullssshit lol

I'm not sure how it works in all honesty.
Maybe if you have an ECU that is flexible it can run the car a bit harder on a more stable fuel? I know the DME on the 335i is able to make quite large timing corrections but if I can I don't want to have any.

[zeppelin101]

Ethanol has oxygen in the hydrocarbon chain which means more fuel needs to be injected to get the same amount of hydrocarbons as straight gasoline. It also has greater latent heat of vaporisation than gasoline (which means it can cool the charge more than straight gasoline can as it vaporises). In the quantities you see in current fuels (10-15%) it makes some difference but not huge. For example, if stoich AFR for normal gasoline is ~14.6, a 10% ethanol mix is usually somewhere around 13.9. The energy density is lower for ethanol fuels too so more fuel is required to generate the same power as straight gasoline (4-5%).

[pointz]

Bp ultimate is terrible makes my car splutter as it comes on boost and as said above causes knock.

Tesco momentum is good if your car is mapped on it/for it in my experience.
My car has the odd splutter on it but my mates sr that was mapped on it was mint.

V-power all the way for me tho (i have 3 shells within 4 miles lol)
Car was mapped on it and its the only fuel that it runs faultless on.


Just make sure your car is mapped on whichever fuel you intend to use and like said if the mapper is good he will safe map it where knock could cause an issue.

Sent from my SM-G925F using Tapatalk

[Mark]

I have run 2 stage 2 200s and 4 standard Focus STs on Tesco 99 which must amount to close to 100k miles without a single issue.