which fuel for a griffith
Discussion
or if not available any of the other brands of super unleaded.
For an article in Sprint I did a bit of research about the 'super fuels' such as V-Power/Optimate. In the opinion of a person involved in the development of one of the fuels and another who was involved in the marketing both agreed that:
that the fuels are worth the extra money,
that the fuels take a time to 'work' on older cars, the older the longer,
that once the optimum is reached then the full benefit can be maintained by alternate fills with super fuel and 95 RON,
that no advantage will be gained by using a fuel of a higher octane rating than the engine is designed for.
I followed, and still follow, the advice and the difference was noticeable from the first fill. The improvements continued and then levelled off. Alternate fillups showed no difference, although I've topped up when half full each time.
The differences for me was a smoother tick-over, quicker pick-up, more performance, lower fuel consumption. I can find no difference between Shell and BP super fuels, but then I'm not the most sensitive of drivers.
that the fuels are worth the extra money,
that the fuels take a time to 'work' on older cars, the older the longer,
that once the optimum is reached then the full benefit can be maintained by alternate fills with super fuel and 95 RON,
that no advantage will be gained by using a fuel of a higher octane rating than the engine is designed for.
I followed, and still follow, the advice and the difference was noticeable from the first fill. The improvements continued and then levelled off. Alternate fillups showed no difference, although I've topped up when half full each time.
The differences for me was a smoother tick-over, quicker pick-up, more performance, lower fuel consumption. I can find no difference between Shell and BP super fuels, but then I'm not the most sensitive of drivers.
willtvr said:
Derek Smith said:
that no advantage will be gained by using a fuel of a higher octane rating than the engine is designed for.
Not so sure about that as I understand that the SP6 is designed to run on 95 but mine have always run better on super - no question.You can set up an engine in a manner which requires higher octane fuel (to put off pre-ignition). This can be done in a number of ways, mainly fuel richness and spark timing, but a lot depends on shape and design of piston crowns and stuff like that. You can require higher octane fuel merely by changing the 'temperature' of the spark plugs.
Using higher octane fuel than the engine is set up for can actually lead to less efficient running, ie greater petrol consumption, due to it running cooler.
A lot is down to temperature control. Part of the problem is that the piston crown is not of a uniform temperature, the bit under the exhaust valves generally being hotter. However, preignition often starts under the inlets.
I have a DFV crown and there is pitting by the inlets yet the metal around the exhaust cutaways is pristeen.
I was told the same thing earlier this year by a very interesting chap in an Essex ECU company so I sort of took it as gospel.
However, this does not, I accept, explain why your engine runs better with higher octane fuel than it is mapped for.
Hoady said:
willtvr said:
Not so sure about that as I understand that the SP6 is designed to run on 95 but mine have always run better on super - no question.
Same here - I always use V-Power. However, it's good to know it will run on 95, just in case you're caught short and no 98 is available.
I need to re-read my manual (98 Griff). I am sure it says 5 star, but will run on 4 star in a pinch. I have occasionally had to use 4 star, and confess I have not noticed any difference. V-Power is the regular tipple. I would not use supermarket fuel.
My other car is an M3, and I can tell the difference between fuels in that. I read somewhere (In Gear in the Sunday Times I think) that the ECU was smart enough to spot the difference and adjust accordingly. 20 bhp more on 5 star is what the article said, and it feels like it.
My other car is an M3, and I can tell the difference between fuels in that. I read somewhere (In Gear in the Sunday Times I think) that the ECU was smart enough to spot the difference and adjust accordingly. 20 bhp more on 5 star is what the article said, and it feels like it.
It mostly depends what the car is 'used' to running on. My 450 chim is fed Tesco 99 and is very happy on it. I give her an occasional fill of BP Ultimate (97) if I cant find a tesco. I tried shell v-power once and things went very pear shaped with poor tickover and poor running. I have heard that cars run regularly on shell v-power will behave in a similar way if you stick BP in them.
Big sticker by my fuel cap says '98 octane only' hence the reason I always use the expensive stuff.
Best bet, ask the current owner what he uses then stick with it.
Big sticker by my fuel cap says '98 octane only' hence the reason I always use the expensive stuff.
Best bet, ask the current owner what he uses then stick with it.
I always use VPower if I can, and try to avoid supermarket petrol.
As for taking advantage of a higher octane rating, most cars are designed to run on the cheap stuff available in their respective markets but modern engine ecus use a knock sensor and can advance or retard the ignition timing to cater for different fuels.
This is not the case for a RV8 TVR as it has mechanical ignition however judging by the fact the car has a sticker saying 98 RON only I'd guess that they were all mapped or tuned to run on 98 only. I can't see the reasoning behind alternating different fuels? Also not sure what the ignition is like on a speed 6
As for taking advantage of a higher octane rating, most cars are designed to run on the cheap stuff available in their respective markets but modern engine ecus use a knock sensor and can advance or retard the ignition timing to cater for different fuels.
This is not the case for a RV8 TVR as it has mechanical ignition however judging by the fact the car has a sticker saying 98 RON only I'd guess that they were all mapped or tuned to run on 98 only. I can't see the reasoning behind alternating different fuels? Also not sure what the ignition is like on a speed 6
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