Hi all

So i started running my car on 98 Ron when i first got it and then went back to standard 95 when prices went up. Have just switched back and the power difference is noticable. I have taken some approx economy and cost figures but could do with a hand working out which is actually cheaper:

98 Ron – £60 a tank – 47mpg
95 ron – £48 a Tank – 42mpg

Tanks size: 45 Litres

cheers

60/47 = 1.276
48/42 = 1.143

The 95 is cheaper

Or another way, 98ron costs 25% more but only improves mpg by 12%

This would be a lot easier if you calculated your fuel consumption in the same units that you buy it in.

I doubt you’re getting a full 45 litres for only £48. It’d be more accurate to work it out based on the £/Litre for 98/95 RON in your area.

What car is it?

Also bear in mind there are many other variables. Different fuels from different brands are not the same, nor are they necessarily the same each day – especially if you fill up at a supermarket.

95 RON petrols are NOT all the same.

I doubt you’re getting a full 45 litres for only £48

Doesn’t really matter so long as he’s putting in the same amount of 95 or 98.

Its a Mito Multiair with 135 bhp from a 1.4 turbo
list mpg is 50mpg combined cycle but i suppose that includes start stop which isnt captured in the dashboard figures ive given

oh and as mentioned they are both filling up from about 1/8th left

Ratio is 7.75mi/£ for 98 and 8.66mi/£ for 95.

Maths says the cheaper is better. Anyone is welcome to shoot down my maths (especially since I can’t be arsed to show working..)

Where can I get 95 ron that cheap?

Quick calc says 7.75 miles/£ v’s 8.66 miles/$

1.4 turbo

Interesting. Non sporty engine but the ECU will vary boost pressure to take advantage of better petrol. Good stuff.

The better petrol might be better for the environment though? I use fancy diesel – the extra cost isn’t quite covered by the extra economy, but the difference is reduced to a few pence per litre – it’s worth it for the smoother running, for me.

As I expected really but it isnt too much more to run 98, the problem is i prefer driving it on 98 but i waste most of the miles on motorways so it doesnt really matter. hummmmm…..

Doesn’t really matter so long as he’s putting in the same amount of 95 or 98.

If it’s just based on cost of a fill-up from when the light comes on, then it’ll not be accurate.

e.g.

95 RON is £1.319/L, so at 4.546L/gallon and 42mpg you get 14.3p/mile
98 RON is £1.399/L, so 47mpg give you 13.5p/mile

I get a different answer to you. Who’s correct?

Of course not but that’s the info he’s providing. Either way, as I posted, 98 costs 25% more, he’s stating 12% more mpg – that’s quite a difference.

I like the flying Ox 🙂

to calculate the fuel used accurately you need to fill the car with one type of fuel – run it, then refill it and see how much you used. Obviously switching fuels you need to make sure you flush out and dilute out as much of the other as you can and you also need to allow the ECU to adjust to the new fuel.

One reason you may be finding better performance on the 97ron is the car has set itself up for it so when you drop down to 95ron it is slightly out. Being a turbocharged engine this is probably more significant than on a NA car.

I would also agree that the brand of fuel will affect things more. I prefer Shell fuel and will go out of my way to get it as the car prefers it and I honestly notice better MPG.

Flying Ox… Based on the numbers he’s given.. I think you’ve got your cost/L wrong.

Yup. But titusrider‘s initial figures are guff (sorry dude) so any calculation based on them will be guff too.

It’s actually cheaper to run it on V-Power.

TSY, that’s what it costs up here for normal Shell and V-Power.

The numbers titusrider gives mean bog standard petrol is £1.067/L and super-unleaded is £1.333/L

Ain’t nowhere in the UK selling either of them that cheap or with such a huge price gap between the two.

The difference in price between 95 and 98 Ron you are quoting looks a bit off. Around my way I’m paying £1.36 and £1.44 respectively at the moment which is just under 6% increase for the better stuff. As you are reporting a near 12% improvement in performance WHERE I LIVE it would seem a better bet for you.

My car (clio 197 – non turbo 2.0 lt) prefers the higher RON. Only snag is that it becomes even more fun to drive and my MPG stays the same or even gets worse as I seem to have no self control.

the Shell v-power gives me more mileage, but other types of 98 ron don’t for some reason.

The extra smoothness and torque are worth it for me, plus there are suppossed to be less co2 emissions and it is suppossed to clean the engine.

non-turbo 2.0JTS alfa engine here, also works better in a 2.0TS.

my MPG stays the same or even gets worse as I seem to have no self control.

+1 unless motorway driving 🙂

I tend to use Shell petrol myself, I’m led to believe the difference in price between standard 95 Ron and V-power is fixed at 8p per litre regardless of the underlying price of the fuel. So as fuel gets more expensive whatever economy benefit you get from the better fuel is amplified.

For example if you get 10% better fuel economy from V-power now that fuel is so expensive its no longer costing 10% extra to buy the more expensive fuel so you come out ahead.

So its a little bit counter intuitive, as fuel get more expensive its tempting to just buy the cheap fuel but this is exactly when the more expensive fuel makes better sense

are the OP’s figures a snap shot from one fill up or averaged over time? There are sooooo many variables you really need to be looking at figures for both fuels averaged over several fill ups. also ignore any data from a few fill ups after changing fuels.

the Shell v-power gives me more mileage, but other types of 98 ron don’t for some reason.

V Power isn’t just 98 ron. It’s 99 for a start, and it also contains various additives to do this and that.

There are sooooo many variables

Yep, you probably need to get someone else to fill the tank so that you don’t know what fuel is in there. The testing needs to be done blind, or even double blind.

You’ll never win a noble peace prize at this rate. 😆

Dr TSY – awarded the noble peace prize for research into fish finger condiments 2010.

I tend to use Shell petrol myself, I’m led to believe the difference in price between standard 95 Ron and V-power is fixed at 8p per litre regardless of the underlying price of the fuel. So as fuel gets more expensive whatever economy benefit you get from the better fuel is amplified.

Nah, because it used to be 2p a litre different, it’s increasing with a %.

the Shell v-power gives me more mileage, but other types of 98 ron don’t for some reason.

I was told by a petrolhead mate that it goes off after a while; so if you buy high octane fuel from an unpopular station, there’s a chance that you’re not getting the full benefit. This is word-of-mouth information so could be horse-poo, but he’s usually a reliable source.

My own personal experience was on the bike (as I’ve driven diesels for ages now). I found that putting in a tankful of rocketfuel gave better performance, but that the benefit stayed for a couple of fills afterwards. So, I used to fill up with the power stuff every third or fourth tankful.

there’s no reason why higher ron fuel should give you more mpg. it doesn’t have any more power held within it than regular ron fuel – its just better able to withstand pre-ignition on a high compression (or forced induction) engine. the only gains from mpg I can forsee would be if the car wasn’t set up to cope with 95 ron fuel (highly unlikly in this day and age) and was pinking all over the place when you were driving on it.

More power, yes (marginally – even on very highly tuned stuff like evos its only around 3-5% difference). More economy – no. I suspect other factors are in play

What’s the point in paying more for something that you set on fire?

the only gains from mpg I can forsee would be if the car wasn’t set up to cope with 95 ron fuel (highly unlikly in this day and age) and was pinking all over the place when you were driving on it

Oddly, modern engines are designed to knock with low octane fuel and use a knock sensor to back off the ignition at higher rpm to avoid it. It gives them better mid range performance and they benefit from high octane fuel.

Oddly, modern engines are designed to knock with low octane fuel and use a knock sensor to back off the ignition at higher rpm to avoid it. It gives them better mid range performance and they benefit from high octane fuel.

yeah that’s what I was alluding to – I’ve not known anything thats set up to run 98ron and doesn’t have a knock sensor in the last few years. There’s probably a couple of oddball cars out there, but even then it’d only really be a big issue at low rpm high throttle openings, once you’re higher in the rev range the issue deminishes

V power every time for me (barring imminent run out of petrol). It definately goes further on a full tank of that. Think I’ve used normal unleaded a dozen times tops in this car when in desperation. It just seems to disappear far quicker!!

Right, so how does retarding ignition timing prevent knock? Is knock the same as pre-ignition? If so, surely it’s something that happens without the spark, which is the problem..?

I’ve not known anything thats set up to run 98ron and doesn’t have a knock sensor in the last few years

Even bog standard cars?

I get approx. 365 miles on full tank of 98 Ron and approx. 330 miles on full tank of 95 Ron.

(I used 95 Ron for about 6 months and now I’ve been using 98 Ron for roughly 10 months.)

Haven’t bothered working out the cost difference.

I have tried BP Ultimate in the Prius and I didn’t notice a big increase in MPG. Problem is it doesn’t commute so does a load of different types of journey on any one tank so there are many other factors.

5lab – Member
there’s no reason why higher ron fuel should give you more mpg. it doesn’t have any more power held within it than regular ron fuel – its just better able to withstand pre-ignition on a high compression (or forced induction) engine. the only gains from mpg I can forsee would be if the car wasn’t set up to cope with 95 ron fuel (highly unlikly in this day and age) and was pinking all over the place when you were driving on it.

More power, yes (marginally – even on very highly tuned stuff like evos its only around 3-5% difference). More economy – no. I suspect other factors are in play

If it’s a forced induction engine, surely it can use higher boost with higher octane rate fuels? Thus it can attain higher torque and you can use lower gears, improving economy.

However using higher gears (as I think you meant) only applies when pootling about, on the motorway you’ll be in top all the time anyway.

I think it’s an ignition timing thing as above. Improves volumetric efficiency no?

Whoops, sorry. Yes, higher gears, not lower.

Retarded ignition timing is likely to reduce burn efficiency I guess?

P.s. I was reccomended to used v-power or similar in my TSI golf (similar engine to the OP), but I’ve not had it long enough to really test for any difference.

molgrips – bog standard cars are *very* unlikely to see any benefit from 98 ron car to start with. The benefits only come when you’re in a highly tuned environment. I think fifth gear did a test which showed no improvement in a shopping car, something around 1% improvement in power in a clio 200 (or something else mildly hot) and around 3% improvement in power in a evo fq 360 (which short of the fq 400 has nigh on the most highly straigned production engine available today). Knock sensors have been standard on cars for over 15 years – because most cars are also sold in countries with very poor quality fuel, the knock sensors help the engine out

with regards to the ‘keeping the car in a higher gear’ – this could, I suppose, contribute, but how often do you change down when an extra 1% power would have meant you didn’t change down? there will be a couple of circumstances, but not enough to make any meaningful difference to your mpg.

I’ve never understood why retarding the ignition prevents pinking/pre-ignition, but it does. I think its something to do with the speed of combustion, but its sadly beyond me.

ah – found the video from 5th gear – it was a clio, golf gti and a impreza. clio got no benefit, gti (warm turbo’d engine) got 2.5%, the impreza got 7%

…so why is my car lying to me and telling me I’ve covered 365 commuter miles with 98 ron against the 330 commuter miles i used to get with 95 ron?