Hey everyone,
just purchased a second hand 307, 51 plate, 1.6LX and my girlfriend has a Pug 307 1.6 Rapier, 02 plate, just wondering what everyones experience or thoughts would be on using optimax from now on in the tank, or an alternative fuel/engine cleaner eg redex,
thanks everyone
Sam
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Personally and this is only my opinion but I think that putting Optimax in a car such as this is just a waste of money. Okay so some will say that you may get more fuel economy but I doubt it will ever cover the extra cost of the fuel. The manufacturers make the cars to run perfectly well on 95ron fuel so why put something else in? Unless your car has been highly modified and needs to use higher ron fuel, don't bother with it and just use a decent quality brand premium unleaded.
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EVO magazine tested this fuel about 12/18 months ago, and without trying to re-write the artical from memory, the fuel gave no economy improvement and a slight performance increase on a BMW, a Jag V8 and a Honda Civic Type R. The performance tests were well done, ie taking reasonable care with measurments etc. They also took before and after photographs of the valve heads, inlet tract etc of the engines. The Jag was very fouled, the BMW very clean and the Honda in between. As a matter of interest the Jag had been run solely on supermarket fuel, the BMW on branded and the Honda on a mixture of both.
After the test all three engines were extremely clean so the Optimax did work in that respect.
I tried it in a BX 16Valve, and to be honest it did seem to go a bit better. I would not use it continuously, but after reading the artical I would use it occaisionaly instead of injector cleaner. The costs would balance out and there isn't the hassle of buying/fiddling with a separate product.
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I would be interested to know whether the fouling was purely cosmetic or detrimental.
I would also be interested to know how much Optimax it took to make the valves clean.
If it was just say one tankful, then maybe it is good for any car to use now and again. but every mililitre of octane improver and detergent is a molecule less useable fuel, also, if the 'fouling' is just cosmetic, then it may be a waste of time introducing harsh chemicals to remove it as they may cause problems elsewhere, such as oil contamination. Just me pondering, I'm neither a fuel specialist or a fuel marketeer.
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I always found my 2002 Xsara 1.6 ran a lot smoother and had a bit more urge about it on Optimax, and I didn't always fill it up myself and I could tell when it had Optimax in. It always felt a bit strangled on anything else and it would pink very slightly at times. That car has the same engine as your 307 so I'd suggest you give some a try. Its only works out a couple of quid a tank more which you don't miss anyway.
On my Focus 1.8 which replaced the Xsara, Optimax and BP Ultimate made absolutely no difference whatsoever, so it does seem to depend on the engine, probably more specifically the management system as to whether there is any performance benefit.
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It depends on how you look at it I suppose, the deposits have to come from somewhere and the engines were not designed with deposits. I suppose that if they were from the fuel then they did not reach the combustion chamber to be burnt anyway. We have to assume that Shell would not add anything which would either inhibit combustion or damage the engine.
I can't remember how long EVO ran the cars for with Optimax in, but it was more than one tankfull. Some simple arithmetic gives the following:-
Injector cleaner is about £15.
Optimax is about 30p per gallon more than standard unleaded.
£15 buys 50 gallons "difference".
50 gallons gives a "conservative" 1500 miles driving.If the fuel is going to do anything, it should do it in this milage.
I'm neither a fuel specialist or marketeer either, I just found the artical interesting.
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What's the compression ratio? That's perhaps the main consideration. Other fuels will give you good additives (Shell and Texaco in particular, according to HJ), but no other fuel will give you 98 RON, which is relevant only if the engine has a high compression ratio.
And what does the manual recommend in terms of RON?
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The compression ratio doesn't really matter, the BX 16V had a ratio of about 10 1/2 to 1 and it ran well on both fuels. A high ron no makes the engine less likely to experience detonation. Unless the engine is running at the right revolutions to achieve maximum volumetric efficiency, with the throttle wide open, then detonation is highly unlikely unless there are any "hot spots" perhaps caused by carbon build up.
The Peugot TU5J4 1587cc twin cam has a cr of 10.8 to 1 and the XU10J4R 2.0 twin cam(Xantia spec) has cr of 10.4 to 1. the recommended fuel in both cases is 95 ron.
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MJM
"The compression ratio doesn't really matter"? I'm surprised. I am no technical expert, but have always understood that the relationship between compression ratio and octane rating was intimate and crucial, although there is tolerance in the sense that you can use high-CR engines gently with lower-rated fuel. Carbon build-up is common, of course, and who can predict when the throttle will be wide open? If high-RON fuels are not about CR, what are they about?
Any other views?
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We've had a lot of debate on the subject of "is Optimax worth it?" before. I know HJ swears by it.
Now, I am neither a petro-chemist nor a mechanic, so my advice is going to be very simple.
Try filling up with it for your next couple of tanks. If the car feels like it runs better with it in, stick with it. If you can't feel a blind bit of difference, go back to what you were using before and save the money.
I use it in both our cars (2003 Honda Civic 1.6 and 2004 Fiat Panda 1.2) and both run more smoothly and quietly, and with better response between about 2,000 to 4,000 rpm. Civic has slightly better economy, although nothing spectacular.
I have no idea why Optimax makes them run better - whether it is because of a more effective detergent in the fuel or the higher octane rating or whatever - but, to me, better running is a good enough reason to continue to use it.
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Compression ratios nowadays tend to be higher than when I started driving. In general engines are better designed especially fuel injection and ignition control and fuel seems to be of a consistant higher quality. I agree with you paulb, try it and see. I did in the BX and decided it wasn't worth it, you have and decided it is.
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thanks all, great help, i am tempted to try it on a few tank fulls see what happens. i'll try it on mine before i tell the other half to go do it he he
Sam
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I am surprised that nobody has raised the issue of which cars are equipped with anti knock sensors. My understanding is that this will control the detonation point allowing a wider range of fuels ie 93-98 to be used without experiencing the traditional pinking effect. This will then surely allow higher RON fuels to maximise power output / performance. Hence the mixed opinions on whether performance improvements are noted with Optimax.
The older high (performance) compression cars should also benefit because many were designed in the days of 98 4star? fuel.
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pmh (was peter)
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