Watch out. The American is confused by European gas, and he has questions...

[HungaryBill]

Alrighty then. Here goes:

In my area I have:

Shell Fuel Save 95(RON)
Shell V-Power 95 (RON)
Mol 95 (RON)
and Mol 100(RON).
To date I've been filling up with Mol 100. But I'm absolutely not familiar with the brand.

First question: Why does Shell have eleventy-billion ratings for their V-power gasoline? I've looked online. It's 95 here, 97 somewhere else, and in some countries it's 100 (but only if you fill up while standing on one foot, have exactly 2.36 bar in your right front tire, and can sing the German national anthem in its entirety before the pump clicks off). Is this just regulatory red-tape, or something else I'm missing?

Second Question: Which would you run? Would you keep it Mol, or go to Shell V-power? (Even if it IS somewhere between 95 and 100 octane, depending on the current phase of the moon, which hand you pump with, and your ability to roll a 7 or above on a 20-sided dice). Why?

Moving on: At the track, I needed gasoline. They only have "Racing 98+". What the heck is up with with this "+" and how does that compare to Mol 100 or Shell V-power? Is that too, determined by my 20-sided dice and how long I can hold my breath underwater, while doing pushups?

The racing fuel is only about 13-pence more per liter in price, and it's worth it to not have to drive 20-minutes (there and back) during my lunch break to get to the nearest Mol station, but that pesky little "plus sign" is driving my pedantic little brain crazy. I need a figure, or a tolerance, or a range, or something! At this point, my sole reason for using Mol gasoline is that it's a finite figure!


Thanks in advance, and many internet points to anyone who can help me make heads or tails of this one.

Cheers,
-Just Bill

[Ollie]

Should be fine on anything rated over 95. Some 8s may or may not drive better on higher octane fuel. It's entirely random and some people swear because it doesn't happen to them how can it be a thing!

As for the differences between 95 and 98 V power, its purely additives. The extra octane is likely there to counteract the less combustible additives in the mix.

You probably wouldn't notice a difference between Mol 100 and V power 95/98. It'll likely be source of original fuel and then the additives mixed in being the only real difference.

If you premix however 95RON fuels can drop down in combustibility, which is just something to keep in mind! I personally stick to Tesco Momentum 99... Just because its convenient and the only other petrol station is a Gulf garage that would be extortionate because small town pricing.

[Honkytonk]

Firstly - it's petrol. Gas is a state of matter which petrol is not in.

Secondly, I imagine you're confused by all this high octane stuff being 'normal', American cars are built to run on what amounts to spicy water.

Okay, sorry, enough yank baiting.

I'm sure somewhere there must exist a list of additives but petrol companies are normally quite guarded about their cocktails. As yorindesarin says, anything over 95 is fine, opinions vary and much hearty debate can be found amongst the pages of the forum about what's best, but typically I think the best advice is to run it on various fuels and see what it likes best, then stick with it. Every car appears to be different, and I think that can have as much to do with its history as anything else.

I would imagine shell have eleventy billion variations primarily because they can (and can market the same product at a bigger mark up) - and as a side thing it probably suits different markets better. In the old soviet union for example, you're going to have cars that were designed to run on Soviet grade 'petrol' knocking about and they don't want their UK fuel mix to blow up some farmers old soviet tractor so probably edit the additives so it suits that market better.

I have a friend who's recently come back from Romania after working out there for 9 months, and he was having issues with the ratty old (UK) lexus ls400 barge he purchased expressly to cart him about on the awful roads - he filled up once at a local petrol station in the boonies and the fuel was the old 92 RON stuff, which the lexus V8 did not take to kindly. Couple of tanks of some decent fuel and the problems sorted themselves.

Anecdotal of course, but a lot of petrol preference is!

[PeteH]

Where are you? It's obviously not England...

The RON is obvious from the number, but nothing else about any particular fuel is obvious. So Shell v-power 95 "may" be better than normal Shell 95 because it may have better additives. But you've no way of knowing.

Racing 98+ presumably means that they guarantee that it has at least a RON of 98. Whereas Mol 100 (for instance) probably has a RON of "about" 100, plus or minus something random. And Racing 98+ could be better in other ways. Or not.

[Honkytonk]

Where are you? It's obviously not England...

Clue might be in HungaryBill's name Pete

[HungaryBill]

Yorindesarin: I do pre-mix occasionally but generally only if I'm headed to the track (what can I say? I'm no exemption to the placebo effect).

PeteH: "Shell v-power 95 "may" be better than normal Shell 95 because it may have better additives. But you've no way of knowing." Exactly why I was asking. I thought this might be normal on this side of the pond, and that you guys might know a bit I didn't. I'm glad I'm not the only one in the dark on this one. In the US they give us 3-octanes of street fuel, and then you pick your favorite manufacturer from there (insert joke about American intelligence here ). Having options that were about as clear a mud was a new concept to me

Anyhoo, thanks gents. Looks like I'll just stick with the Mol 100 for now as it seems to be the one that has the least amount of variations. Maybe I'll ask Santa for a dyno-day this year and bring a few cans of gas out with me to see what can be determined?

HonekyTonk: I'd try filling up with each and jotting down my thoughts, but there's no way my butt-dyno is anywhere near calibrated enough to get any sort of results from just driving around (unless it was very very prevalent). It does sound like a good excuse to do some b-road blasting though!

Cheers y'all

[PeteH]

I just wanted to reiterate what was said below. The RX-8 is designed to run on RON 95. Choosing a higher octane number than this is theoretically pointless. A higher octane number is only required if the engine is at risk of detonation (pinking, pre-ignition, whatever you want to call it), but the RX-8 is tuned to be a long way from detonation because rotaries tend to destroy themselves if they detonate, so Mazda designed it to be a long way from detonation. The energy content of every fuel variant is approximately identical, and the stoichiometric ratio is also approximately identical, so there is no way that an RX-8 can produce more power by using "better" petrol.

There are just two ways that better petrol can help:
1) If it has better additives then it may help keep you engine free from carbon build up. So (theoretically) if you use expensive petrol then you may have a more healthy engine after tens of thousands of miles. Frankly, any RX-8 that spends a reasonable amount of time being driven fairly hard isn't going to suffer carbon build up, whatever fuel it uses.
2) If your engine isn't perfect (i.e. has carbon build up, or dodgy ignition), or if it has been tuned (boosted or ignition timing altered), then your engine may be more likely to detonate than Mazda intended. In that case better petrol can help protect against detonation, and is therefore an extra layer of safety. If your engine is healthy and well maintained then this doesn't apply.

And there is a potential downside to posh petrol. It's possible that if you change to a better petrol then the additives in the expensive petrol may dislodge carbon, which then gets caught on the seals or the ports, and creates engine damage. But this is probably rather rare.

There have been may discussions on here about which petrol is "best". There is no firm conclusion. Some people swear that their engine only runs well on 98 RON v-Power, or 99 RON Momentum (a UK supermarket brand which is the highest octane rating we have here). Other people swear it makes no difference at all.

What do I use? Mine's a 100% race car, but with a stock engine. I use 98 RON Shell v-power. Because there is no reason not to, and for the 600 miles a year that I do it doesn't exactly break the bank!

[kopite72]

Just my two bobs worth but all we have in Ireland AFAIK is 95 RON but whenever I'm in the UK I use shell V Power and the engine runs much better. Its silky smooth, in fact the very first time I used Shell V Power it was instantly noticeable how much better the car ran as opposed to what I was used to

[New Duke]

I agree Ian. Peter's explanation is clear, educated and makes total sense. So I'd never expect 99 fuel to make more power or be safer. Nor do I worry about putting 95 in. I'm sure it's just as fine.
But my car does also noticeably run smoother on 99. I've tested it lots over the last few years to be sure I'm not imagining it. Can't say how or why, but I can see the difference.

[warpc0il]

Sent from my SM-G800F using Tapatalk

[Ollie]

Its really hard to explain the difference if you've never experienced it first hand. For the sake of however much more petrol cost per year I don't mind running premium. I feel like the car deserves the best even if it makes no difference or a literal hair of difference.

[v-rex]

My 2 cents.

When I got the Prodrive day at MIRA a few months after I bought my PZ, the chaps there said although the car doesn't have a specific mapping for higher octane fuel, higher octane fuel will run cooler and so will still provide an advantage and they recommended it.

For the 13 years I've owned my car, I have mostly used shell v-power which is 98 ( or might be 99 now actually ) and it's been good to me. When I got this advice petrol was closer to 100p a litre, and in fact at one point around 2008 I seem to remember it was around 80p and so wasn't a big issue to go high octane. When fuel got ridunculous at one point I did switch back to 95 octane for a couple of years but the car felt rougher, and I swear it gave less mileage per tank.

I switched back to shell v-power and never looked back. All my personal experience and no opinion on other brands, sorry, but I thought I'd post in case it's useful.

[RenesisRaceBuggy]

Never made any difference when we dyno tested it, as already stated, the '8 isn't limited by fuel knock for it's ignition timing anyway. Adding more timing with higher octane fuel gives you nothing but more risk.

[Nerdstrike]

On the topic of the variable RON, I think it might relate to regulations (or choice) on how much ethanol they can cut into the fuel. Adding ethanol raises the RON. Then there's the differences in calculating RON between US and the UK (if not the rest of Europe?). In the end, V-power nitro + is the additive package to the fuel, and not the fuel that comes from the refinery.

Pumps in the UK are starting to display ethanol content in each fuel with E5, E10 etc. Owners of older cars should welcome this.

The RX8 does not care for high RON fuels, but individual cars seem to like one over the other (but this is as much in the mind of the driver as in reality I'm sure, even though I believe my RX8 liked high octane more than regular).

[warpc0il]

Pumps in the UK are starting to display ethanol content in each fuel with E5, E10 etc. Older car owners should welcome this.

I assume you meant "Owners of older cars" rather than "Older car owners", as some of us are getting on a bit.

Anyway, I qualify on both counts and my '68 Alfa Romeo doesn't really like any ethanol content.
Even 5% isn't recommended and 10% puts many components in the fuel system at risk.
We welcome being told, so/if we have a choice.

Back in the day, the Alfa was recommended for a minimum of 4-star fuel, though she ran really well on Avgas, when I used to work for Hawker Siddeley

While we're reminiscing, I recall touring France many times in the 70s with groups of bikes.
In France you had a choice of "Essence" or "Super"; the former was one step up from paraffin and the latter about 3-star in UK ratings.
The Nortons, especially with the combat engines, would run like a bag on nails on Essence and didn't even really like the Super.
The Yamaha and Suzuki 2-strokes loved Essence and went like stink on the stuff, not so much on Super :shrug:
The Hondas, BMW's, Ducatis, Laverdas, etc didn't seem to care much either way and Essence was a fair bit cheaper.

[geofftl1000r]

If Shell have to use a marketing word like "Dynaflex" to describe it's 30% more cleaning molecules in V-Power, then I wonder what a load of old crock it must really be.

On a recent bike trip to the Ukraine I came across a lot of stations selling 100 octane fuel. I rebuilt the engine recently and this included a head skim so the compression is a bit higher. The engine was actually noticeably smoother with 100. This wasn't the case pre-rebuild.

I stick with Shell V power in the 8 as it's popular among people on the forum and it does have Dynaflex!!! Might give that Tesco's 99 a try next fill up.
The nice thing about the 8 is, no matter what you put in the tank, it won't be too long before you can try something else!

[warpc0il]

I was working for Shell, both Shell UK and as an internal consultant to Shell International, in the 80's when "Formula Shell" hit the headlines, for all the wrong reasons.

With an office in Shell-Mex House in the Strand, and another in Shell Centre on the Southbank, I did a lot of hurried walking back and forth over the old Hungerford Bridge for a few months

I've still got a whole load of Formula Shell branded merchandise (mugs, brolly, bag, jackets, etc) after they pulled it from the UK market - not one of our finest moments.

[MARKTHOMASBRAND]

[kopite72]

That pic is very apt for rotary owners

[Nerdstrike]

I assume you meant "Owners of older cars" rather than "Older car owners"

Sorry, a poor turn of phrase on my part. I was attempting to refer to the age of the vehicle.

[Shagrington]

So I recognised Eileann Donan Castle and Glencoe in the advert - quite possibly there was a part of the NC500 in there too.