Juice

[matt_c]

Conflicting information. I have been told to use only Super unleaded (97ron), but the sticker beside the fuel cap states 95ron - normal unleaded. Which should I be using??
I have put 95ron in, and every now again (happened 5 times in 6 weeks), the engine gives a major cough then carries on as normal (this might not be fuel related though).

[T88CAN]

Most Tuscan owners run on Shell optimax only, however
there is no problem with normal 95 ron with the exception supermarket fuel? The car tends to run that little bit smoother on optimax

[beano500]

matt_c said:

.... every now again (happened 5 times in 6 weeks), the engine gives a major cough then carries on as normal (this might not be fuel related though).

I had the same problem when I used to drink cheap blended whiskies, now I stick to single malts.

Go for Optimax - you know it makes sense!

[GI Jnr]

OPTIMAX!

at the very least, 97 RON fuel. The little extra backfires make it all worthwhile!

Tuan

[mcspreader]

I find that the main reason for the engine giving a big cough isn't fuel quality but quantity. If the tank is very full and the breather is a little blocked then a vacuum will develop and the car will cough like a consumptive 200 a day man on Mace.

[matt_c]

Thanks for the comments... so why do TVR specify 95ron fuel???

mcspreader... I shall look into your explanation next time it happens!...

[whitey]

The engine is mapped by TVR to run on 95 octane. As it's a high compression engine and the quality of petrol does sometimes vary, it's better to be on the safe side and run on higher octane. Also the additives of Optimax and Ultimate do apparantly help keep things cleaner inside the engine.

[Alf Essex]

Only feed mine Optimax

Alan.

[anonymous-user]

My dealer specifically told me NOT to use optimax etc... and to only use 95 RON unleaded. (03 Tuscan 4.0)

[matt_c]

We need to resolve this one.... !

[jigs]

Surely it just depends on what the individual car's timing has been set to at the pdi/last service.

[matt_c]

It also depends on compression ratio, and the dealer can not alter this...

[mesh]

Lower octane fuels, among other things, can cause detonation or pre-ignition in the combustion chamber(CC). Detonation occurs when the pressure/temp within the CC is raised causing the fuel air mixture to auto-ignite. This goes on to produce multiple flame fronts, instead of one, and when they collide they cause a sudden rise in cylinder pressure accompanied by a sharp metallic or knocking noise commonly known as "pinking" Remember anything tht raises the pressure/temp within the CC can bring on pinking but if your car stops pinking when you use a higher octane fuel then it's probably a good thing to continue using it. For all the boffins out there I know this is a fairly simplistic view so feel free to ammend/add if it will help.

>> Edited by Mesh on Wednesday 18th February 08:55

[matt_c]

You are correct about the pinking, but my engine doesn't pre-ignite with the 95ron fuel.
Perhaps this means I am safe to use either 97 or 95 ron fuel.......

[Mesh]

Sorry Matt I wasn't trying to suggest your engine does pink, mine is the same v happy to run on 95 ron and no difference if I put good stuff in. Lucky us eh!!

[matt_c]

oooh a choice!! Lucky us indeed!

[graham66]

I was talking to John Ravenscroft (the Speed Six engine designer) and he said he is not allowed to recommend any one fuel above any other, but he uses Optimax and the engines he has taken apart that have been run on Optimax have all been a lot cleaner than other engines run on other fuels - that was enough to convince me to top up with Shells finest wherever possible!!

Graham

[andyvdg]

The engine is mapped to 95. 97+ is recommended for track days. You won't get any better performance running on Optimax, but it'll keep the engine clean and it should run better on part throttle.