[E90F30er]

For unleaded petrol which is the best: Shell, BP, Esso, Total, Texaco, the 4 big supermarkets, others.
For super unleaded petrol similarly?

I have this weird theory in my mind Tesco unleaded is the "best" supermarket one because their super unleaded Momentum99 is 99 RON - a higher RON than the others!

EDIT: diesel as well if you wish

[Proftinkerpot]

Momentum and Shell V Power are not higher quality but a fuel blend which as you say has a higher RON or Octane rating then standard fuel which is 95 or Super Unleaded which is 97. Some cars are tuned to run on a particular grade while other modern vehicles can adapt to them by advancing or retarding the ignition to prevent engine knock which is caused by the fuel igniting too early in gh combustion cycle. My Impreza is mapped to run on 97 or higher. If I was stuck and had to use 95 Ron then the car retards the ignition to prevent early detonation. Most people think the higher the RON the more combustible the fuel but it's actually yer other way about. Don't automatically assume your car will run better on dearer fuel. It may do but equally your ECU may simply adjust itself to maintain things the same. There is a misconception that higher RON fuel adds bhp - it is actually that lower Ron fuel reduces bhp in certain circumstances. Check the handbook then try different products for yourself. I found my Impreza ran noticeably better on BP Ultimate then it did on Maxol or Sainsbury super unleaded. Unfortunately 99 Ron is not sold in Northern Ireland any longer so those relying on it must use a fuel additive such as octane booster.

Hope this helps.

[Tengocity]

Originally Posted by E90F30er

For unleaded petrol which is the best: Shell, BP, Esso, Total, Texaco, the 4 big supermarkets, others.
For super unleaded petrol similarly?

I have this weird theory in my mind Tesco unleaded is the "best" supermarket one because their super unleaded Momentum99 is 99 RON - a higher RON than the others!

I suppose it depends on what you mean by "best"?

Performance gains? More efficient? Engine protecting?

I've tried to test the economy of super unleaded and premium diesel before but couldn't show any difference. No idea whether to believe any of the claims on additives to protect the engine. So in my eyes fuel is fuel is fuel, and I use what is cheapest and convenient.

[EvilDrPorkChop]

I always get a higher mpg figure when using Texaco or Shell regular diesel, I gain about 30 more miles on a tank. It's because the supermarket fuels use quite a strong bio diesel mix, therefore it isn't as good of quality of fuel.

I find also that the car seems to idle a bit smoother, but there isn't a great difference.

Edit: Sorry only just realised you were on about Petrol only!

[dopper99]

Originally Posted by Proftinkerpot

.....There is a misconception that higher RON fuel adds bhp ...........

It DOES add BHP. I think it was Fifth Gear that put 3 cars on a dyno a few years ago with 3 different fuels. The Impreza gained quite a bit more BHP and torque.

[dopper99]

On the other hand Fifth Gear also did a test on fuel additives that you can buy in a bottle that were supposed to boost the cars power. I think all of them actually REDUCED the cars power!

[Tengocity]

I think the differences between fuels would be so minute that any performance increase, or that of smoothness is likely to be a "placebo" effect, as much as anything.. your mind sees what you hope to see (and what the marketing wants you to believe).

I tried to check the figures in terms of economy but there was no discernible difference (compared 5 tanks of premium v 5 tanks of standard) except to the bill at the end of it!

I would like to know more about the additives that "protect" your engine, but I am pretty sceptical to say the least.

As it happens, Shell is by far the most common station I pass, and the prices are ok so that's what I use mainly, but I have no issues with using supermarket fuel if it's what is most convenient when I fill up.

To be fair I have looked in to this a lot more with diesel than with petrol. I do use Super unleaded when i do a track day!

[crazybones]

Fifth Gear undertook a more recent test in 2012. The verdict was that premium fuels are probably not worth the additional cost.

However, unlike the previous test, they did not appear to reset the ECU between tests, so I wonder if the cars did not fully have time to adjust to the different fuel types:

[jwickers]

Not even sure if the brand would be consistent, i have 2 same brand gas stations and i found one of them gave me significantly worse economy on the same fuel. Could have been a fluke, an issue with their tanks or just that we happened to drive differently at the time ...

Also the dealership gave use 2 boxes of fuel additives when we got the car which i am guessing are octane boosters though i am not too sure if they are even necessary (haven't noticed a difference using them or not).

All seem like snake oil to me ..

[DazC]

I always used to use shell v power in my imprezas.

Shell Nitro is also meant to be good.

[Nick the Greek]

99RON will make no difference over 98RON.
BMW quote all power and economy figures using 98RON.
95RON will loose you circa 5% power.

[bwrlane]

I have a diesel. Using premium fuel doesn't seem to make any difference in power or economy, but it makes a difference to the sound. Less dieselly with premium fuel.

[E90F30er]

Heinz baked beans are typically better than the supermarket own brand in taste and flavour. But supermarket fuel comes from the "same" refinery as fuel company brands?

Question:
Petrol v diesel - "suppose" if the mpg and price per litre were IDENTICAL which one would you choose?

[Proftinkerpot]

Dopper I think the reason the Imprezas gained power was that they are factory tuned to run on 97 or higher. My 07 STiwith a Prodrive Performance and the Prodrive certificate stipulates it as a requirement. Some earlier Jap imports were factory tuned for even higher Ron fuel.

E90F30ER - You are correct that fuel all starts at the same refinery and storage tanks then particular fuel companies add their specific additives.

[MarkG_M5Comp]

Originally Posted by Proftinkerpot

...then particular fuel companies add their specific additives.

Shell adds lubricants & stuff, Tesco adds corn syrup, Asda adds water.

[Proftinkerpot]

Very good Mark lol

[Rich9600]

Originally Posted by bwrlane

I have a diesel. Using premium fuel doesn't seem to make any difference in power or economy, but it makes a difference to the sound. Less dieselly with premium fuel.

Totally agree. My car may also be a bit more responsive on the posh stuff, but no more powerful. I put it in every 4th tank, this seems enough to keep the diesel soundtrack to a minimum.

I've been doing this since summer. I drove back from France on cheap French super diesel, by the time I got home my car was running the sweetest I've ever had it. Cumulative effect of a good long run clean out and now every 4th tank of super diesel also seems to have increased fuel efficiency marginally.

But as above, mostly an acoustic difference.

I'll run in my new 330d on it, as it can't do any harm and may do some good. Better ignition timing or lubricants?... My local station is BP and I think this is who BMW recommend / get a back hander off...

[NISFAN]

Originally Posted by crazybones

Fifth Gear undertook a more recent test in 2012. The verdict was that premium fuels are probably not worth the additional cost.

However, unlike the previous test, they did not appear to reset the ECU between tests, so I wonder if the cars did not fully have time to adjust to the different fuel types:

Modern ECU's adjust 'on the fly' hundreds of times a second. They no longer learn long term, so no need to reset them.

[ukbeemerboy]

Originally Posted by E90F30er

Heinz baked beans are typically better than the supermarket own brand in taste and flavour. But supermarket fuel comes from the "same" refinery as fuel company brands?

Question:
Petrol v diesel - "suppose" if the mpg and price per litre were IDENTICAL which one would you choose?

That is really down to personal preference. I drive a 330d, not because I do mega mileage a year but because it gives me 520nM of shove (more than an M3). I prefer the drive of a diesel.

[Tengocity]

Originally Posted by E90F30er

Question:
Petrol v diesel - "suppose" if the mpg and price per litre were IDENTICAL which one would you choose?

I like the characteristics of both diesels and petrols, but refer each in different situations. Motorways and cruising are the ideal situation for a diesel, where in-gear shove and low-end torque are important.

But for A-road blasts, on the track, and general driving for fun , then the noise, throttle response and top-end of a revvy petrol are more enjoyable to me.

Just one car, then probs the petrol tbh

[Steve C]

Mon-Fri diesels, Sat-Sun petrols

[crazybones]

Originally Posted by NISFAN

Modern ECU's adjust 'on the fly' hundreds of times a second. They no longer learn long term, so no need to reset them.

Yes, that makes sense given the power of modern ECU's.

I've compared several tank fulls of Shell Nitro to normal unleaded and it really does not make a significant difference to fuel consumption. The MPG gain was less than 1mpg and well within normal fluctuations.

Subjectively, the car feels a little more responsive at the top end, but it's certainly not worth the price premium IMHO.