91, 95 and 98 Unleaded

[FH]

hello everyone,
I took my girl friends VW polo (20k miles) into a VW garage with a misfire... They had to strip it down to find out that due to a carbon build up 2 valves had burnt out.... which is shocking for a 4yr old car driven by a school teacher! They said we should use 98 unleaded and if we had used 98 from new this wouldn't have happened....

So... my question is, Should I use 98 in my car?? Elise S2 51 ST (Rover k)? What does everyone else use?

Your Advice would be much appreciated! Thanks

Have a good weekend. Drive safely!
FH

[timh]

The story of a VW Polo needing super unleaded sounds like total B*ll*cks to me, have had many VW petrol cars and covered over 100k in each and NEVER used 98 ron fuel, NEVER had a problem either, Shell optimax and some other fuels have detergents to help stop the build up of kack around the valves but it sounds to me like they were fobbing her off.......

As for the Lotus, the K series does not have a knock sensor on it so it will make no difference if you use 95 or 98 ron, just that the 98 ron will cost you more. It's up to you if you thinks it's worth paying the extra for shell optimax for the cleaning properties

Regards

Tim.

[NJS25]

Carbon deposits can be caused by continuously using the car for short journeys, or at the bottom end of the rev range.

If the car has been driven in this manner, carbon builds up excessively and never gets burnt off from good hard thrashing.

In this circumstance using Optimax, or similar, would have reduced the carbon deposits due to its cleaning properties. So technically the dealer is correct, however, considering what market the polo is aimed at and the age of the vehicle I would be extremely unhappy with this excuse. It shouldn't happen, but could.

Personally I only use fuels from branded stations, and will use Optimax occassionally. Not all fuel is the same, cheap fuel is cheap for a reason. We had a local problem, a supermarket destroying engines with water contaminated fuel. Using sub-standard fuel would further accelerate the carbon build up.

If the car in question has been driven in this manner and fed on this type of fuel the result in not surprising.

Regards, Neil

[ju.]

This is an example why a car with low mileage is not always the best bet cars driven on alot of short journeys build carbon up really badly and this contributes to poor running. As for keeping the carbon deposits at bay you should use optimax which apparently prevents it or treat with redex every so often

[FH]

Thanks!

Yes the car is almost exclusively driven on short journies... but it does seem a litte premature... They r going to ask VW for goodwill jesture contribution... fingers crossed.

Thanks for your advice/opinons - Really appreciate it. cheers.

(we have a polo 1.4 loan car while repairs are being done.... You know, I might just have a quick go in it!!!)

[shangani]

By all means consider optimaz from the "cleaning" point of view if that is to be believed, but you will not gain any performance advantage vs 95 octane. The k-series lacks a knock sensor and the ecu does not make specific adjustments to the fuel type. This has been argued in previous topics, but the lotus blokes themselves said 98 octane would NOT make a difference unless other mods were made to the engine. Whether this applies to the Toyota engine I do not know.

[[k]ar|]

Any anecdotal evidence on using super-unleaded fuels in the 111r? I queried Lotus directly about this when I bought the car, and they said there was no performance benefit, but Optimax would keep things clean.

Curiously, although I accept it may be placebo effect, my car seems to go further on a tank of optimax than regular.

[k]

[go4it2]

In the book for the 111r it states, use unleaded petrol 95ron or above...from memory.

On my old S2 (k) i always used optimax or similar, i always got more miles for my pound and the engine felt smooth. This is even more so for the 111r so far and I think it must have the knock sensor, why say use 95 or higher?

[bogie]

"why say use 95 or higher?"

...mmm....because that basically means any grade of Unleaded available in the UK ! ?

[barrad]

One of the reasons many people think you go further with a tank of the likes of Ultimate or Optimax is that they contain anti foaming agents. When you fill up, less foam is produced on the surface of the petrol in the fuel tank and so the cut out detector on the petrol pump cuts in slightly later.

[Towzer]

I had an Impreza a few years ago and it HAD to be run on 98 RON or higher, put 95 in it and the thing would be pinking like mad. Apparently the japs design their engines on higher RON levels as that's what is available to their domestic market. On this basis (and my speculation!) the Toyota engined 111R would have been designed to use 98RON or higher.

Phil

[bogie]

Towzer - yes you are correct...Ive had JDm imports before that have a sticker inside the fuel cap with "100RON only" on them ...and some JDM versions of cars are like 20bhp up on the UK versions due to this...but remember the deal with Toyota and Lotus was that Lotus had to provide and map their own ECU for the engine...which they did....for 95RON.......

my Audi S4 has a knock sensor and being a turbo its noticably different in power output when running on 98 or 99 RON

[telecat]

VW Golf Mk5 1.6 FSI's have a little sticked inside the filler flap instructing users to use 98 RON petrol. Might be worth checking the website.