Daft question I know. On filler cap states premium unleaded E5. Tesco also sell unleaded E10 at 30p litre cheaper. Can I use the cheaper one.
What model MX-5 have you got. By the book, NC and later you can use either…
More modern cars are fine on e10 but it didn’t exist when the earlier models were made and as such it’s not really recommended for cars built pre mid 2000s.
I personally use e5 super even in my 2014 nc because my car is used intermittently and I prefer higher octane e5 sitting in the tank than e10. E10 gives slightly less mpg (ethanol by volume is apparently 33% less efficient than the equivalent in unleaded petrol), absorbs moisture more readily due to the higher ethanol content and can be more damaging to seals and other components on a car never built to use it. Can also cause detonation especially if your car is an earlier Japanese import as these were designed to run on high octane fuel in Japan.
There are various websites where you can type in your reg and it will tell you if it’s OK to use, but if you have an na, nb or early nc I would personally avoid it. 
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Mine is a mk3 2007. I use car all year round though I only drive no more than 2,500 miles and short journeys. Sometimes just 2 miles a day
With zero hard data to back it up, I perceive slightly higher mileage per tank on premium fuel. I don’t notice any performance benefits. Local to me, I am paying 10p a litre more for premium fuel which doesn’t seem too pricey when adhering to manufacturers recommendations.
I have no concerns in using standard fuel if on a trip and it’s all that’s available when it’s time to top up.
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30p/litre cheaper? It’s usually 6 or 7p cheaper at the Tesco where I fill up. I put E5 in mine. It may be confirmation bias but I think it drives better. Anyway, nothing’s too good for The Precious.
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I found the E5 prevents low-rev flat spots and makes an NC much more tractable, eg when in slow traffic.
More importantly (usually I avoid slow traffic) it tends to give me better mpg than the same brand of E10, and the percentage differences of cost and mileage cancel out, giving me very similar p/mile.
The other great advantage of something like V-Power is how clean the engine and exhaust run, no worries about EGR cloggage etc.
On the Skyactive Mazda3 on one family holiday, when forced to use E10 I was also forced to drop down a couple of gears at 70 for a gentle hill we usually took in top with the V-Power. The motorway mpg coming home from Cornwall on that tank-full of Texaco E10 was 20% worse than usual with V-P!
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At £4 a litre what’s the merit in putting some of this blue stuff in a near empty tank when/if you lay up for winter. I use it in my mower and 2-stroke hedge cutter to stop the petrol turning to caramel.
"Aspen 4 is the cleanest petrol that you can use. Aspen is made from alkylate petrol which is made from the gases from the top of the distillation tower which are synthetically modified into a liquid again.
The result is;
a petrol that is virtually free from sulphur, benzene and aromatics (solvents)
is ethanol free
is chemically inert – can leave the fuel in machinery and will start easily next time"
E5 of the Tesco or Sainsbury’s variety, runs smoother although it did have an engine tune to 180bhp.
I’d seriously change fuel stations if you are paying 30p more over E10, even your Shell and BP’s station aren’t that much dearer.
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Shell or Tesco premium unleaded E5 every time for me.
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Since I p/x the NC for the ND 12-months ago, I have only used E5 Shell V-Power. As mentioned above, and I have no data to support this, but I feel cars run better on E5. And as for mpg, the second trip on the car shows 9,432 miles covered in the last year at 52.6mpg. The other trip zero’d frequently has shown 61.2mpg on a modest run from Doncaster to Lincoln, with 54’ish generally at the moment. I suppose some quicker bursts every now and then when I feel the need, drops the averages a little bit.
For me the extra few pence is worth paying.
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I don’t know whether it still is, but V-Power petrol was GTL (gas-to-liquid) fuel at one point. Whether 100% or not I couldn’t say.
Not very scientific but I think I get 2-3mpg more in the 1.5ND from E5 97-99 RON than from E10 95 RON (4%-6%). You never really know what the ethanol content is anyway - the 5% or 10% are the maximum, not a prescribed proportion.
I refuse to pay up to 20p/litre premium for V-Power but the extra for Esso and BP Supreme/Ultimate is a bit lower. And the Greenergy Momentum 99 RON E5 from Tesco is only about 7p extra.
There is a lot of profiteering on road fuel in the UK at the moment, especially on diesel.
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Definitely a to-each-their-own topic.
Personally there isn’t much I can control on a car, but petrol is one of them. I use RON 99. I didn’t pay thousands and thousand and thousands of pounds on cars to then penny pinch over a few quid at a petrol pump.
I used to exclusively use ESSO’s 99 as where I am it used to be ethanol free (even though the pumps still said ‘up to 5%’, and I even wrote to then to check). However, since last September that isn’t the case anymore, so I’ll use that or V Power, or Momemtum.
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Just between you and me (no one else is looking) 
I got it wrong. Unleaded is 5p cheaper not 30p 
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Yes, I wondered what Tesco you were going to 
That’s great, around us it’s usually 8p or 10p more depending on which supermarket you go to, Tesco/Sainsbury’s.
My NC was always run on E5 unless it was unavailable (just didn’t see E5 on the last 2 holidays in Scotland). The new ND is currently running on E10 as that’s all my local station has to offer, unless I drive up to the motorway service station, but that’s usually 1p or 2p per litre more expensive across the board. If was doing less tha 2,500 miles per annum I would definitely spend the few pennies extra and go for a branded E5 petrol.
Thanks for all your thoughts
I am one of those saddos that does brim to brim calculations on all three of our cars every fill up.
My conclusions over many years of collecting data is that there is no identifiable difference in mpg for either diesel or petrol between ‘ordinary’ and ‘super’.
However there does seem to be a difference in the way they ‘feel’ when driving. On the Caterham it picked up much cleaner and removed all the ‘popping and banging’. There was no difference in outright grunt.
On the 5 with ‘super’ it will pull much longer and harder up an incline before the change down light is illuminated. (The 5 is the first car I have seen where the gear change light is not speed related.)
The Mini is now run solely on ‘super’ and feels the same as it used to do on ‘ordinary’.
The Volvo diesel did feel ‘brighter’ on ‘super’.
My conclusions are that subjectively there was a difference but my factual calculations indicate no difference.
Having made this general, and (as it turns out) not entirely accurate statement the other day, I needed to fill up this morning and decided to look in detail at local prices which I haven’t done for a while. The results shocked me.
Tesco’s price differential for E5 vs. E10 now varies from 9p to 12p locally. Only slightly more than I remembered. However I paid a ‘bargain’ 153,9p for BP Ultimate 97 RON this morning, 10p more than their E10, but the other BP station in the same town is charging 169.9p, an extra 26.2p above the E10!
I thought it was worth posting this - we can no longer assume that E5 will be reasonably priced. I’ll be checking in future.
Prices were from https://petrolmap.co.uk/ , and the https://www.petrolprices.com/ app.
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