|
the higher the RON the slower the combustion , i think... preventing knock ... but it sounds like an air leak if your pinking
|
|
|
>> >> What car is it? >>
A Smart Roadster that my son has just bought.
|
|
It will not damage it;all engines used in the EU must comply and are performance checked to a legal directive which requires the use of 95 octane;yes,some engines will give a little more performance on higher octanes but they MUST be able to run on 95.
|
HJ had a view on this in last week's Telegraph. The questioner had posed a similar question about a MK5 Gti. HJ was emphatic that 98 octane should be exclusively used.
From last week's paper.
Q I have just bought a VW Golf 2.0T GTI FSI. I understand it should run on super-unleaded petrol, which is more expensive than standard unleaded. How important is this?
R.D., via email
HJ Extremely. I find Shell V-Power to be best in terms of cost and benefit. You will contaminate the fuel system and lose about 20bhp if you use standard unleaded. Why buy a high-performance car if you want to run it on low-grade petrol?
Edited by Pugugly on 12/04/2008 at 13:04
|
On the MK5 Golf GTi, 98 is the recommended choice however, 95 can also be used but will sacrifice a small amount of power (from handbook, while printed on inside of fuel filler flap - large '98' with a smaller '95' in brackets beside it).
Here in Northern Ireland, I am not aware of anywhere that sells 98 octane. There is no Shell V-Power and no Tesco 99. 97 is however readily available through most of the major players which I am sure is more than adequate for cars needing the higher octane rating.
|
|
I wonder how owners of classics fare? I seem to remember my father's Rover 2000TC had to have 101octane!
|
|
|
|
HJ Extremely. I find Shell V-Power to be best in terms of cost and benefit. You will contaminate the fuel system and lose about 20bhp if you use standard unleaded.
I can understand that using a lower octane may lead to lower power output. But how would using 95 Octane petrol 'contaminate the fuel system'? Can someone explain?
|
Comes down to the basic premise of getting what you pay for.
I am a firm believer in buying "branded" fuel if I can, especially in my bikes which tend to be more sensitive to inferior quality petrol. For this reason if I have to use a supermarket I always use the premium option if it's available.
I learned from a reliable source some years ago that Tesco et al do not add extra aromatics (anti-knock and performance enhancing chemicals) to their regular fuel, unlike Shell, BP etc. Basically this means that their premium fuel is about equivalent to BP or Shell regular.
I will no doubt be disagreed with on this issue but I rarely have fuel problems.
|
|
Thanks all. I wonder what the contaminant referred to in HJ's reply to the reader might be?
|
Sulphur. 98 octane is sulphur free - less than 10 ppm. From UKPIA: "Additionally, sulphur-free petrol is "enabling technology" in that it optimises the efficiency of new direct injection petrol engines that improve fuel efficiency and reduce emissions of carbon dioxide when combined with de-NOx exhaust catalysts." The process of changing all fuels to zero sulphur has to be completed by 2009, but lower octane petrol still has up to 50 ppm. tinyurl.com/4bfvgj
As I mentioned some time back!
|
|
Sulphur-free 95 is also available.
|
|
|
Some cars need high octane petrol. A friend has a Mk 1 Golf GTI. Her husband used to complain that it pinked. I advised premium fuel and a dose of injector soap. He said, but the book says it can run on ordinaire. I said, well, it can, but it pinks because it would prefer premium stuff. Buy it the good stuff and it won't. Eventually they did, and it stopped pinking. Big surprise.
|
|
|
|
I can understand that using a lower octane may lead to lower power output. But how would using 95 Octane petrol 'contaminate the fuel system'? Can someone explain?
When it comes to the calorific value (i.e. the energy it contains) petrol is petrol. The octane rating is merely a measure of it's anti-knock properties and depends on what additives it has in it. If your car will run happily on 95 octane then there is nothing to be gained by using 98 octane. However, if 98 octane is specified by the car manufacturer, then by using 95 octane you run the risk of the engine "knocking" aka "pinking".
|
|
And loss of power due to ignition being retarded. Those who rode bikes with an advance/retard lever will know what the engine feels like when retarded: hot, sluggish and generally off:)
|
>>I wonder how owners of classics fare? I seem to remember my father's Rover 2000TC had to have 101octane!
My old Vitesse was the same, 100 octane recommended. It was never the same when they withdrew it. I had to retard the ignition, and enrich the mixture on the twin carbs. Oh how I loved trying to balance them!!!!!
There's a petrol station not a hundred miles from here still selling leaded (NOT LRP). Just behind it's a small Imp specialist!
|
|
With a classic you have to retard the ignition a bit or use an octane booster.
|
I googled for "octane rating" and found several articles explaining it. Here's one such tinyurl.com/5947y6
|
|
Proper Leaded petrol is available all over the country;not cheap but certainly available.
|
As a child 50yrs ago I remember my dad's old Bentley had three levers arranged arround the central horn button. One was to advance and retard the ignition. I think the idea was to advance it till it pinked slightly, then retard it till it didn't.
Another was the supplementary hand throttle - a sort of early cruise control! Can't remember what the third one was...possibly choke/mixture.
My job on long journeys [e.g.Cornish hols from Yorkshire] was every 250mls to push a lever in the passenger footwell which allegedly pumped grease into various parts of the suspension.
One really had an intensive mechanical working relationship with cars in those days!
|
If it was a Rolls (Derby) Bentley one of the levers would have been to adjust the hardness or otherwise of the rear shock absorbers. Never made any perceptible difference though in any Rolls or Bentley I drove or drove in.
The centralised chassis lubrication system was another Roll-Royce thing. It used SAE30 engine oil, not grease, and lubricated the clutch withdrawal bearing, the steering joints, the front suspension and the leaves and shackles of the rear springs, which were encased in leather gaiters to keep the oil in. To work properly though it had to have the right sort of 'drip plug' at all the escape points in the system, which was 'total loss' and over time made a pattern on the garage floor.
|
|
My old Daimler Conquest has this automatic chassis lubrication system. There's a chamber near the exhaust manifold which heats up when the engine runs, the oil expands and is forced through to the joints etc. It's supposed to be a one-shot system, just operating when you first start but of course it leaks. These days most people run them with a thicker oil rather than the specified sae30. You can always tell where an old Daimler has parked.
|
I had a 51-plate VW Golf 1.6petrol that knocked and pink'd like a good'un when run on regular 95 octane stuff. Was terrible. Went into dealer several timesto be looked at - in the end the dealer not only told me the knocking was because it was being run on regular fuel, they actually told me that if the engine failed due to the pre-ignition it would not be covered under warranty.
Sold the car shortly afterwards!
|
If it is a newish car the engine management system should compensate for the slight drop in octane level, so I do not believe it will have any adverse affect on engine.
This may result in a sight decrease in performance though.
Give it a go. In the short term there will certainly be no detrimental effects and this will allow you to evaluate if there is any unusual differences, such as lumpiness or pinking under load.
If so you just revert back to the cheapest 98 RON you can find.
|
>which were encased in leather gaiters to keep the oil in.
Trivia alert,
The springs were all made in the Spring Mill at Samuel Fox (now Corus after passing through United Steels, British Steel and GKN) in Stocksbridge, South Yorks. Before delivery they were coated in light grease.
The leather used for the gaiters was very high quality and RR would refuse to accept any spring if there was even a scuff or scratch on the leather.
Kevin...
|
|
|
|
HJ Extremely. I find Shell V-Power to be best in terms of cost and benefit. You will contaminate the fuel system and lose about 20bhp if you use standard unleaded. Why buy a high-performance car if you want to run it on low-grade petrol?
What exceptionally poor advice. There is simply no way you would lose 20bhp by running 95 ron instead of 97/98 ron.
|
|
IIRC Fifth Gear ran tests on several cars and found a similar loss/gain on an Impreza turbo. I can't remember the exact numbers though. There was little or no difference on 'cooking' cars.
|
|
Evo (issue 87) tested a range of fuels on a GTI Golf which requires 98 octane for optimum power.Nearly 10% torque difference between the worst (95 octane) and the best (BP Ultimate). The latter outperformed a race fuel in mid range. Bearing in mind that a dyno only measures torque, and the hp figures are calculated, HJ is correct. I suspect he has a little more insight into car manufacturers reasoning than some who are quick to criticise.
Edited by nortones2 on 19/04/2008 at 11:36
|
Had an R1200R BMW on loan the other day. Mentioned 98ROZ (sic) by the filler.
Is that different to 98RON?
|
Some cars do run 'better' on higher octane fuel, my old Mercedes 190E 1.8 springs to mind. It was a bit of a slug on regular. I also got better MPG on super.
People on the Vectra forum also recommend super for the 2.0T engine, which I own, but I haven't tried it - quite happy with the performance and MPG I get on regular branded fuel.
|
Had an R1200R BMW on loan the other day. Mentioned 98ROZ (sic) by the filler. Is that different to 98RON?
Only in terms of the language - IIRC, Zahl is German for number.
|
Interesting one this, I filled up in Bristol today and given that V Power was only 4p more than regular back in Aberystwyth where I'm from, I thought I'd see if it made any difference.
Given I have a 2 year old Ka, so no performance gain really expected:
- Responsiveness as opposed to outright performance, does seem better
-I got 37mpg from a tankful, which includes getting from Devon back to Bristol in an unmentionably short time (if I say three figures were maintained on the motorway for most of the way, I'm talking kilometres, honest.)
Last two tankfuls have returned 36 and 35mpg respectively trundling around town as opposed to hammering it up and down the motorway at 90-100. I'd have to fill it with V and with regular a couple more times, but I suspect the higher octane V has helped consumption, given how I drove today!
|
Given I have a 2 year old Ka ..........
Have a look in your car's handbook. My Ford (admittedly not a Ka) handbook says there is no advantage to be gained from using petrol having a RON greater than the specified 95.
|
My Volvo's handbook says to use the highest octane fuel available for maximum performance and economy. It specifies a minimum for continuous use of 91 RON, and that 87 is acceptable for occasional use.
I've run it mostly on 95, but in the early days, I switched to 98 for four tankfuls, and could detect little difference. Perhaps a tad sharper on part throttle, and a paltry 1 mpg improvement, but in no way did it offset the £4 extra per tankful.
Cheers
DP
|
Mrs P's GTi is run exclusively on the posh stuff, I noticed on Friday that the price differential seems to be lower.
Car goes like the wind :-)
|
Bloke next door to me, a German fellow, is one of the test drivers for Bentley. Employees of Bentley can have a choice of VAG cars on cheap monthly rates. They keep them for about six or nine months. Anyway, this guy had a Golf GTI last time and reckoned that they had put it on a measured test to see if the grade of fuel really made a difference. He is absolutely convinced that performance and mpg is adversely affected on this engine by using standard octane fuel.
As an aside, all sorts of interesting kit with suitably rumbly engines turns up on his drive when they are testing things. I see it as passive security for my house. Who's going to burgle me when there's a supercar or luxury limo on next door's drive ?
;-)
|
In reply to AlanGowdy I have a Smart Roadster and run it on 95 unleaded with no problems.
If you read the handbook it says that if 98 octane is not available in your country the car can be run on 95 without harm. If so performance will be reduced and fuel economy worse.
No doubt the ECU recognises pinking (knock) and retards the ignition a tad.
On my 1925 Bullnose Morris,which preceded the Smart, you had to alter the advance/retard yourself with a lever on the steering column-the Smart thinks it out for you!
In view of the increased price of 98 I don't think it is worth it.
I still get more than 50mpg in a very hilly area, and the performance is still enough to frighten me!!
When I had my car serviced at a well-reputed Smart specialist he said he used 95 in his own Roadie when he was doing a long commute to work,without problems, and he was happy with the performance.
These cars are such fun to drive that a second off the 0-60 time is hardly relevant.
Put in the cheapest 95 you can find and enjoy it-you are also only putting out 121gm CO2/km-one of the cleanest cars around.
|
|
|
|
|
