premium unleaded - really??

[bella]

i've just bought my first petrol car in 8 years, and i've got a feeling it's going to want me to put posh unleaded in it.

obviously it depends on the engines and perhaps it's difficult to generalise, but really... do i have to? what difference will it make? can i alternate?

[RPD Motorsport]

It really does depend on the car. 90% of all cars will not be fussy. Most performance cars will run knock sensors and have adaptable maps - so will run either, but you may loose 2% peak power - so what on the road?

Some performance cars though - super cars (ferrari, lambo, aston etc...) and also Evo's have very specific non-variable engine maps. So they are made using a 99 RON or whatever fuel, and the map is set to always run on the performance limit of the fuel - regardless of load. This means that if you use a lower grade fuel then you will suffer engine knock issues which reduces power, fuel consumption and engine life. More advanced maps will only run on the fuels limit when on 100% load.

So if you are buying a 'normal car' it will make sod all difference! The other advantage of 'super fuel' is more down to fuel quality. It is significantly cleaner and has a lot of cleaners in the mix, so looks after engines better. In my motor I get more milage per £ with super than normal as it suits my map. Just try each on a set run over a week and see.

[bella]

i probably should have said which car - it's an 06 audi s3, uses the 2litre turbo petrol engine.

my old man has been trying to put me off the car using the "you're going to have to put premium in it" line (failed, i bought it anyway), but i don't really see the need to on a constant basis. but as my original post suggests, i don't really know much about it and impartial knowledge seems hard to come by!

i'll give the comparison a shot - i'll run asda grade rubbish in it for a week, then spank on a bit of the premium stuff. performance isn't really an issue for me on a day to day basis, but on the long road trips i'd prefer not to be doing it any damage.

[garcon]

bella, I'll ask on a forum full of Audi fans - they should be able to advise (probably with a truckload of conflicting posts... ).

I would say 98/99 RON would be advisable but not essential. To get the best out of the engine it's certainly worthwhile every few fill ups - but that depends how the engine management reacts to each tankful.

Tesco 99 is good stuff btw.

[bella]

Originally Posted by garcon

Tesco 99 is good stuff btw.

that was my next question! good. it's bad enough being parted from my 70mpg long drives, let alone losing the joy of clubcard points

[Steven Humphrey]

I had a Seat Leon Cupra a few years ago, which had a 1.8 turbo engine, the same one used in the S3, TT & Golf GTI. Seat recommended super unleaded, which I used for several years. Then, when fuel sky rocketed, I used normal unleaded & noticed no noticeable difference whatsoever. Power seemed the same & economy was no different. Maybe the engine wasn't running as clean but I didn't notice. As a compromise, you could alternate between the 2 types for each fill up.

[GORDON STREETER]

You might notice a difference on a dyno but I would doubt if you would notice any increase on the road.
You might think so because you have paid more for a fill up !

[garcon]

The consensus from owners of Audi 2.0TFSIs in various guises on another forum I visit is that 98 RON is recommended, and will definitely provide an edge in terms of performance, economy and refinement. That said, 95 RON won't actually do any harm and the ecu will automatically detect what you filled up with and adjust.

Given that Tesco 99 is only 5p a litre more than 95 RON, to me it's a no brainer - might as well treat it right and get the best out of it.

The consensus is also that you should take it to a reputable after market tuning company to release a few more gee gees. A quick google of 'Shark Performance' will lead you to one of the best.

[Steven Humphrey]

I remember seeing a test on (I think) Fifth Gear ages ago-they tested super unleaded in a 1.2l Clio, a Golf GTI & a Scooby (relating to power increases). The Clio had no extra power, the Golf abot 2bhp extra & the Scooby 20bhp extra. Basically, the higher initial bhp, the more benefit from using super.

[bella]

Originally Posted by garcon

The consensus from owners of Audi 2.0TFSIs in various guises on another forum I visit is that 98 RON is recommended, and will definitely provide an edge in terms of performance, economy and refinement. That said, 95 RON won't actually do any harm and the ecu will automatically detect what you filled up with and adjust.

Given that Tesco 99 is only 5p a litre more than 95 RON, to me it's a no brainer - might as well treat it right and get the best out of it.

The consensus is also that you should take it to a reputable after market tuning company to release a few more gee gees. A quick google of 'Shark Performance' will lead you to one of the best.

thanks garc - i'm a bit iffy about maybe causing engine damage, but if there's no concerns with that then i think maybe every other splash of fuel will probably be 99. iirc our local tesco has it so it's not going to require a special journey.

more ponies isn't an immediate concern, not until i get schooled off the lights by a diesel at least

[andrewc]

I've recently changed cars. Japanese Import. 2 litre 210ps non turbo, manual gearbox.

So far I've proven to myself, that on my routine commute I get:-

a tank of standard supermarket fuel will get me 265 miles.
a tank of standard shell will get me 275 miles
a tank of supermarket super unleaded 97 will get me 301 miles

I've got a tank of Tesco 99 on the go at the moment and I want to try Shell V-Power as well.

These have all been routine journeys and not longer runs, so I feel are more suited for comparison.

I've yet to work out whether the added expense of the different fuels is worthwhile from both a financial point of view, but also from a long term engine cleanliness view as well as the premium fuels tend be better at keeping injectors clean.

[VIVA GT]

Bella, with the "I'll put super-unleaded in every few tankfulls" routine, I think you're getting confused with the procedure when genuine leaded four star was becoming scarce. (Not something that you'll remember personally, but maybe a story from your parents?).
The theory then was that as long as you accasionally used leaded fuel in the car, the lead additive would 'save' the valve seats as it is supposed to, but you could 'get away' with using non-leaded fuel most of the time. (In truth, this sisn't really work out either on many a Metro engine for example!).
I'd suggest that you stick with the better quality, super-unleaded wherever possible (but if you can't get any, ordinary unleaded will be OK, just don't push the performance). As others have already said, Tesco Super 99 is reputed to be a good fuel, and isn't a stupid price.
At the end of the day, using better fuel should give you a better return on the fuel economy, plus it should lessen the risk of (expensive) damage to your lovely new high performance engine.
Let's face it, you wouldn't expect an Olympic athlete to perform at their best if all they ate was junk food would you?

[BertMk2]

Originally Posted by VIVA GT

At the end of the day, using better fuel should give you a better return on the fuel economy, plus it should lessen the risk of (expensive) damage to your lovely new high performance engine.

But it's not a high performance engine is it? It's a mass production 2 litre with a turbo and a new ecu map. It's mildly tuned at best - we're not talking supercar or massively tuned to the limits screamer here are we? (No offence Bella - I'm not trying to belittle your shiny new purchase)

Originally Posted by VIVA GT

Let's face it, you wouldn't expect an Olympic athlete to perform at their best if all they ate was junk food would you?

True, but going back to my previous point - it's not an Olympic athlete, it's someone who does a bit of jogging (and likes a kebab or two )

[bella]

Originally Posted by VIVA GT

Bella, with the "I'll put super-unleaded in every few tankfulls" routine, I think you're getting confused with the procedure when genuine leaded four star was becoming scarce. (Not something that you'll remember personally, but maybe a story from your parents?)

haha no, i'm quite old too. we didn't have an unleaded car for quite a while, it was only with the dodgy 1.6 ford orion that unleaded happened for us as a family

i was purely thinking in terms of diluting the additives and that sort of thing. me putting 99 and 95 in probably comes to a happy medium the car wouldn't be too anxious about

the irony is i drive like a grandma, i just fancied getting as much for my money as i could. it was either a 2 litre petrol with *all* the toys or a 2 litre diesel with *some* of the toys plus an engine and a set of filters that would more than likely not agree with my driving style. hence i find myself trying to establish the daily grind of petrol engines

interesting on the economy figures andrewc supplies though - those extra miles can be quite important at the end!

Originally Posted by BertMk2

But it's not a high performance engine is it? It's a mass production 2 litre with a turbo and a new ecu map. It's mildly tuned at best - we're not talking supercar or massively tuned to the limits screamer here are we? (No offence Bella - I'm not trying to belittle your shiny new purchase)

none taken - it's a purchase i somewhat stumbled into because of the above mentioned price/toys/value equation. it's something i can either hang onto till it explodes, or sell off in 6 months if it isn't sustainable in terms of fuel bills. in the meantime i want to make sure i get the most from it both as a car, and preserve it as an investment. its been treated very well by its previous owner, so it's a very nice little car.

[grantp]

bella,

Run it almost dry, fill with 99 Octane and take it on a track day.

You'll probably blow over £100 on fuel and the same or more on tyres but you will know what it is capable of delivering.

Then take it home and nurse it as would a chauffeur. It's a relationship thing.

[bella]

fwiw i checked the manual last night (i'm a girl, i'm allowed to read the instructions ) and it agrees with the info garc sourced - it says that it does prefer to run on 98 for optimum performance, but the engine is happy with 95 with a slight downgrade in performance. anything less should be considered an emergency measure.

seems fair enough

[Adam43]

Put 95 in and make up for it in the corners

I do find the 98 better for fuel, but if you push on that goes away, obviously. I have never seen a benefit in the more expensive diesel? Might just be me though.

[bella]

a further note to this - i've put asda 95 in it this week (for 10p a litre less, tidy), and it has definitely taken the edge off the performance, particularly at high revs. i'm finding that i have to use the gears a lot more to get anywhere near a similar sort of pace as the 99 gave me.

it's actually quite handy - it's a bit too much of a lunatic for everyday commuting on 99 rocket fuel, but on 95 it's a lot more driveable. the turbo doesn't seem to pick up as quickly with 95 which for me makes motorway driving a lot more economical. the temptation to give it inappropriate and wasteful beans is a lot less too.

[thebear]

A definitive explanation of the "Premium Fuel" arguments by Dennis Simanaitis, the Engineering Editor of US car magazine "Road & Track".

http://www.roadandtrack.com/auto-new...m-fuel-futures

[bella]

i can honestly say i didn't understand a word of that. all i gained was that our standard cheap fuel is considered premium fuel in the states for starters, so it's kinda irrelevant for the uk.

[JHamilton]

Originally Posted by bella

i can honestly say i didn't understand a word of that. all i gained was that our standard cheap fuel is considered premium fuel in the states for starters, so it's kinda irrelevant for the uk.

That's not correct. It's the same fuel, but a different a different nomenclature. The article applies to the UK as well.

98/99 RON = 93/94 AKI "High-test"
97 RON = 92 AKI "Premium"
95 RON = 89/90 AKI "mid-grade"
92 RON = 87 AKI "regular"

More than likely you will not notice a difference in performance on the street, but you will notice a mpg difference by using a lower octane fuel. Depending on the price of fuel, this may or may not make sense for you. In my case it does not as if I use regular in my car I lose 1mpg and 2-3 in the truck.

[bella]

it's semantics really, our "regular" isn't the same as your "regular"

but bearing in mind what you suggest, it's odd since i've noticed a significant difference in performance between 95 and 99, and as a result the 95 is actually proving to be better on fuel economy evidently it depends on how your car manages the difference in fuels.

fwiw i was going by this in the article:

Our premium fuels typically have pump octanes of 91–93. Regulars are 87 octane; midgrades, 89. (Why a midgrade? We’ll get to this in a moment.) And, of course, befitting its name, premium fuels come at a premium price, currently in our region 20¢/gal. beyond regular.

hence suggesting that 90 is premium cause it said 89 was midgrade

incidentally, whilst we're on the topic of cross-atlantic differences, at what point do people in the states put a higher grade fuel in their car, and what do you think tends to be the motivation for doing so?

[JHamilton]

I think most put the recommended fuel in their car. Entry level cars usually take regular gas and performance/luxury cars take higher grades. So those that can afford the car can afford the gas without thinking about it. That being said, you pay roughly twice the all time high price for fuel here right now. Therefore, maybe we do not think about it as much although we drive much further on average.Although it is changing quickly, there are not many turbocharged cars here. In my experience, using a lower octane fuel makes an huge difference in performance on any forced induction car, particularly turbos.

There are also many people that believe that their car runs better on a high octane fuel even though it is not recommended. This misunderstanding is throwing money out the window.

[thebear]

Originally Posted by bella

incidentally, whilst we're on the topic of cross-atlantic differences, at what point do people in the states put a higher grade fuel in their car, and what do you think tends to be the motivation for doing so?

Almost all cars sold in the US for the past ~20 years have been specified in the owner's manual as run on "regular" (87 US/92 UK) with the exception of BMW(s) and obviously performance models (Corvettes, some Mazdas, some Nissans and the `hot' VWs).

BMW `purists' always go for their specified 98/99 RON = 93/94 AKI "High-test". They also state that they can `feel' the difference.

I have owned '88, '93, '94, '97', '02 and '04 Nissan Maximas with the 3.0 or 3.5L V-6 and keep very accurate records of my fuel consumption. The current one is the '02. My mileage has been detrmined by where I drive rather than how. I was determined to see if "High-test" really made a difference on 1500 mile trip primarily on motorways at 70 + mph. It was perhaps 1 mpg better but I could not discern any `performance' difference.

An early "failure" of our government has been "up to 10%" Ethanol content which over the past few years. It has really degraded the fuel economy of the cars. Whereas my '97 Maxima was good for 25-27mpg (plus 20% to convert to Imperial gallons) it dropped to 23-25mpg and it had the 5 speed as opposed to the automatic boxes in the others. Automatic boxes are the mainstream and manuals have all but disappeared. Later model years have better adapted to the Ethanol.

Another variable is the time of year and geographic location. Because of the vast land area and climate differences in the US, at any one time there are as many as six different blends of any grade of gasoline natiowide. All are produced to match emission regulations with climate variatons. It is of course transparent to the motorist.

From time to time I have encountered gasoline brands that were significantly poor for mileage over several tanks and avoided them. Strangely enough the brands produced no difference in consumption in other cars I have owned at the same time.

Driving habits are the main contributors to poor mileage for 95% of the automotive population. Specifially not anticipating the changing of traffic lights which is strange. US traffic lights cycle from Green to Amber to Red so there is adequate warning. The other 5% can be attributed to idling in traffic at traffic lights.