Normal unleaded (95 RON) OK in a 2004 S4?

What does the Owners Manual state?

My TT225 manual (and my previous S3) says 98 RON, but 95 RON is OK but with reduced performance.

AFAIK, only Shell Optimax is 98 RON in the UK. Superunleaded has been 97 RON for several years.

Personally, I use Optimax with Octane booster.

-- Doug Ramage

What does the Owners Manual state?

My TT225 manual (and my previous S3) says 98 RON, but 95 RON is OK but with reduced performance.

AFAIK, only Shell Optimax is 98 RON in the UK. Superunleaded has been 97 RON for several years.

Personally, I use Optimax with Octane booster.

-- Doug Ramage

Higher-octane unleaded (I hesitate to call it "Super", 'cos that's the name of 95RON in most of Europe) in 97 simply because that's what 4-star was)

Optimax is 99RON, I believe equivalent to the old 5-star (just a dim memory for me ;o)

As Doug says, there should be a specific entry in the manual to reassure you.

H1K,

IIRC, Optimax, in the UK, was/is supposed to be around 98.6 RON (Shell only claim that it's "greater than 98 RON"). However, some test(s) seem to indicate it was nearer to 98.3 RON.

I seem to recall that elsewhere (Germany, Australia?) than the RON could be

99?

-- Doug Ramage

I presume that this is going to be a company-owned car - would they rather pay for a new engine when it breaks?

I don't know about the S4, but the owner's manual for the RS6 warns against using full throttle when running with 95 RON, and also says to fill up with Super Plus ASAP. It also instructs you to 'only use moderate engine speeds and a light throttle'.

So I think that one would be ill-advised to run 95 RON on the RS6 for an extended period. I have concluded that nothing less than Optimax is good enough for my beast (and this from someone who has maintained a prejudice against Shell - I hadn't used a drop of Shell petrol since the dabacle in the late 80s when Shell 'New formula' wrote off many brand new engines, particularly Audis).

If you do find that the S4 would be better off with higher than 95 RON, your best bet might be to add some Millers (octane booster) with each tank full of 95.

You presume incorrectly: its my car. The company pays (not unreasonably) for business miles done in my car. Unreasonably, they have recently introduced a new rule stating that they won't pay for Super Unleaded (which I guess they figure is just a waste of money).

Well I now have the owner's manual. When I asked the question, the car hadn't arrived yet - just got it a couple of days ago.

Mine says the same.

Thanks for all the help guys. I think beating up our "cost conscious" finance director sounds like the best course of action! And failing that, Millers.

Chip.

I assume you are UK based? If so, the new mileage regime for business use (w.e.f. from 6 April 2002) is limited to 2 rates only - 40p for first 10,000 miles and 25p thereafter, irrespective of engine size, cost etc. If the rate(s) paid are less, then you can claim the difference from the IR. If higher, you will have to pay income tax on the excess. The old option of being reimbursed action cost (or a percentage thereof) is no longer available. Nor will you be able to claim depreciation (Capital Allowance) nor the interest charge to finance the vehicle's acquisition.

Therefore, the cost of the fuel is irrelevant to the employer. In fact, for VAT purposes, the employer would be better off if you bought superunleaded/Optimax, as the VAT element *increases* with cost.

-- Doug Ramage

Yep. And how many cars can be run at a cost of under 40p per mile? The old 63p/mile limit under FPCS was bad enough. I haven't worked out figures for my RS6 yet, but I would imagine that it's somewhere around

150p/mile (depending on depreciation).

Usually only small cars with diesel engines. :)

-- Doug Ramage

Well not referrin to economical matters I´d rather say that if you don use such a kind of petrol you are surely going to damage your engine. Why?

Simple in the four times of a explosion engine and particularly in the very time of explosion the engine is calculated to make a certain pressure depending on the power of the car. If your car is sorted to use 98 oct because of its explosion power and you don´t feed it so your transmission and the cilinders bar inside can get damaged.

Good luck with negotiations or get your boss to sign a maintenance contract just in case.

"Doug Ramage" escribió en el mensaje news:bjspln$ml9ja$ snipped-for-privacy@ID-34015.news.uni-berlin.de...

unreasonably)

Blow me - they do indeed state that. I guess when it came out someone rounded the number, then someone else noticed, then..

As goes tests, the octane rating reduces over time (remember the problems in F1 a few years back, when some fuel hadn't "aged" quite as much and got a team disqualified..?)

H1K

Four star was orignally 98. Five star was 100 minimum. In fact IIRC Shell's five star claimed to be 101.

I think five star had already disappeared by the time they sneakily down-graded four star to 97 RON, which was roughly at the same time that unleaded 95 came in.

The Digifant Golf GTIs had the same warning in the owners manual about slight loss of performance and not using full throttle. I seem to recall that I didn't notice any difference, so I usually used 95 - but I rarely if ever used full throttle anyway.

Regards

Jonathan

[snip]

Its not irrelevant to my employer (unfortunately). They pay for my petrol. Its nothing to do with what I can/cannot claim tax relief for. The company pays for it, so I get taxed on the benefit. But the tax (less the amount I can reclaim) is still a lot less than if I have to pay for the actual petrol!

Still, its all very stupid. They will pay for diesel (77p/litre), yet not Super Unleaded (80p/litre) 3p difference is hardly going to break the bank is it.

And here's the really stupid thing: I can buy any car I like. They will pay for the petrol for a Hummer at maybe 6 mpg.... as long as I don't put Super Unleaded in it! How bloody ridiculous.

Chip.

I understand what the company are trying to do. However, have you pointed out the extra admin hassle thier method causes them? If they paid the IR rates (or below), the company would not have to re-calculate the figures to see if a benefit arises which has to be reported on P11D form.

Rules is rules. :)

Agreed -not logical.

-- Doug Ramage

But the RS6 is a turbo, while the ('04) S4 is not. I would certainly

*hope* that any modern normally aspirated engine with electronic ignition would be equipped with knock sensors to allow compensation for low octane.

-- Mike Smith