So why Optimax
Discussion
I think the speed 6 runs a bit smoother at lower revs on higher octane fuel, but you won't get any more power higher up. It is supposed to keep the engine clean inside. I read the article in EVO when they ran cars on cheap petrol and Optimax, and then stuck a probe inside to have a look - you really could see the difference.
Since then I've always tried to use expensive fuel, mostly Optimax. I'm told however that the bits added to the fuel that make the octane higher only last a week before going off....
Cheers,
Andy.
Since then I've always tried to use expensive fuel, mostly Optimax. I'm told however that the bits added to the fuel that make the octane higher only last a week before going off....
Cheers,
Andy.
andyvdg said: I think the speed 6 runs a bit smoother at lower revs on higher octane fuel, but you won't get any more power higher up. It is supposed to keep the engine clean inside. I read the article in EVO when they ran cars on cheap petrol and Optimax, and then stuck a probe inside to have a look - you really could see the difference.
Since then I've always tried to use expensive fuel, mostly Optimax. I'm told however that the bits added to the fuel that make the octane higher only last a week before going off....
Cheers,
Andy.
I'm lucky if it stays in tank a week, using it daily for work.
Right you technophobes, why am I filling up with Optimax. Its only on recommendation, but I dont notice a difference. Or does it all happen in the engine?
Mr Heath has a nice section on his website about optimax fuel and unleaded - www.tvrbooks.co.uk go to the FAQ's and then unleaded fuel and optimax.
Ian
>> Edited by rustoni on Tuesday 1st April 08:32
Caution. Optimax is an HDHO fuel, if a high octane fuel is not directly recommended by the manufacturer for road use because the management cannot adapt you run the risk of plug fouling in traffic. Optimax has a very high detergent content, not a problem in a modern engine, but in an older design it can cause severe valve recession and also fuel leaks from its effects on seals-shouldn't be a prob. on a Tuscan, but I wouldn't want to risk it on a V8 engined Tiv.
Any unleaded will cause valve recession in a vehicle without hardened valve seats. However, Optimax is said (by the CAA) to cause problems in more recent engines with hardened valve seats and with some types of seal and is not legal for car-engined aviation use. My mechanics (I half-own a small gas-station with a workshop and MoT testing station) have been seeing a lot of smoky petrol Discoveries, Range Rovers and early Mondeos with bad valve recession. The common factor seems to be owners noticing their engines running a bit rough, then using Optimax for a few months to see if this will solve the problem. Obviously there is a chicken/egg scenario here, but in Australia, where Optimax has been available for longer than it has here, Shell flag up that it may not be suitable for older cars, even with hardened seats fitted.
Edited to add: Optimax is an excellent fuel for use in a modern EFI vehicle, higher octane giving slightly smoother running, and high detergent levels keeping the injectors clean and helping to avoid carbon build up in the chambers. But it may not be appropriate in an older engine design.
Please don't sue me Shell. I'm not dissing your product-you mention plug fouling and valve recession on your websites. Thankyou
>> Edited by mrsd on Tuesday 1st April 09:56
Edited to add: Optimax is an excellent fuel for use in a modern EFI vehicle, higher octane giving slightly smoother running, and high detergent levels keeping the injectors clean and helping to avoid carbon build up in the chambers. But it may not be appropriate in an older engine design.
Please don't sue me Shell. I'm not dissing your product-you mention plug fouling and valve recession on your websites. Thankyou
>> Edited by mrsd on Tuesday 1st April 09:56
I think you've hit the nail on the head here....owners already noticing "engines running a bit rough", but there is some circumstantial evidence as you say. I'm sure time will tell, but its a mite worrying. Particularly to car owners who all but have to use super unleaded petrol.
Thanks for that.
Thanks for that.
Isn't every day in a Tuscan a potential "track day"?! 
>> Edited by robkola on Wednesday 2nd April 09:16
>> Edited by robkola on Wednesday 2nd April 09:16
>> Edited by robkola on Wednesday 2nd April 09:16
andyvdg said: Factory recommendation on Tuscans is 95 octane (normal) fuel for normal driving, 97+ octane (Super) for track work.
.
>> Edited by robkola on Wednesday 2nd April 09:16
>> Edited by robkola on Wednesday 2nd April 09:16
>> Edited by robkola on Wednesday 2nd April 09:16
mrsd said: Any unleaded will cause valve recession in a vehicle without hardened valve seats. However, Optimax is said (by the CAA) to cause problems in more recent engines with hardened valve seats and with some types of seal and is not legal for car-engined aviation use. My mechanics (I half-own a small gas-station with a workshop and MoT testing station) have been seeing a lot of smoky petrol Discoveries, Range Rovers and early Mondeos with bad valve recession. The common factor seems to be owners noticing their engines running a bit rough, then using Optimax for a few months to see if this will solve the problem. Obviously there is a chicken/egg scenario here, but in Australia, where Optimax has been available for longer than it has here, Shell flag up that it may not be suitable for older cars, even with hardened seats fitted.
Edited to add: Optimax is an excellent fuel for use in a modern EFI vehicle, higher octane giving slightly smoother running, and high detergent levels keeping the injectors clean and helping to avoid carbon build up in the chambers. But it may not be appropriate in an older engine design.
Please don't sue me Shell. I'm not dissing your product-you mention plug fouling and valve recession on your websites. Thankyou
>> Edited by mrsd on Tuesday 1st April 09:56
Your depth of knowledge on many subjects is awesome!
mrsd said: Any unleaded will cause valve recession in a vehicle without hardened valve seats. However, Optimax is said (by the CAA) to cause problems in more recent engines with hardened valve seats and with some types of seal and is not legal for car-engined aviation use. My mechanics (I half-own a small gas-station with a workshop and MoT testing station) have been seeing a lot of smoky petrol Discoveries, Range Rovers and early Mondeos with bad valve recession. The common factor seems to be owners noticing their engines running a bit rough, then using Optimax for a few months to see if this will solve the problem. Obviously there is a chicken/egg scenario here, but in Australia, where Optimax has been available for longer than it has here, Shell flag up that it may not be suitable for older cars, even with hardened seats fitted.
Edited to add: Optimax is an excellent fuel for use in a modern EFI vehicle, higher octane giving slightly smoother running, and high detergent levels keeping the injectors clean and helping to avoid carbon build up in the chambers. But it may not be appropriate in an older engine design.
Please don't sue me Shell. I'm not dissing your product-you mention plug fouling and valve recession on your websites. Thankyou
>> Edited by mrsd on Tuesday 1st April 09:56
Your depth of knowledge on many subjects is awesome!
One comment, whilst the V8 in TVR's is an old design this does not necessarily mean that components and major parts of the engine have not been re-engineered by TVR e.g I doubt that the cylinder heads, which is where the valve seats are, would be the same as originally built by Buick
mrsd said:...it may not be appropriate in an older engine design.
Rich... Blimey, didnt realise this subject was so involved. Have read the posts several times, but still not sure what the actual conclusion is. 
Is it a "yes" to the wife Lady Topaz carrying on using Optimax or should we go back to 95. PS agree to the deference to mrsd's knowledge. Thanks to all!
Is it a "yes" to the wife Lady Topaz carrying on using Optimax or should we go back to 95. PS agree to the deference to mrsd's knowledge. Thanks to all!
RichB said:One comment, whilst the V8 in TVR's is an old design this does not necessarily mean that components and major parts of the engine have not been re-engineered by TVR e.g I doubt that the cylinder heads, which is where the valve seats are, would be the same as originally built by Buick
Absolutely. The possibility of wear (as may be occuring in other Rover V8s) is something I personally would be keen to avoid though. I would also have doubts about the seals in older fuel pumps etc.
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