Does Optimax Make A Difference?

[mensa]

Hi All

I have to confess I used to think Shell Optimax was a load of rubbish!

I used to have a 1.6 Mini One (90bhp) and whenever I tried Optimax it never made any noticeable difference. This experience put me off spending the extra pennies on what seemed like a waste of time, until now!

I recently thought to myself why not, I have been driving my T sport for one and a half years using the cheapest fuel I could find, so I took the plunge and put £40 of Optimax in.

At first I thought to myself, Nice 1 Simon, what a waste of money! But after a day or so I began to notice a definite improvement in the performance of my TS.

The car seems faster, smoother and I seem to be getting about 2-3 more mpg(canceling out the extra cost :D )!

Is this just wishful thinking, or have other people had the same experience?

[GRD008]

Fifth Gear (the TV program) once compared all the fuel types available in the UK and then put the test cars on a dyno to see any differences....

their test cars were a clio, golf gti and an impreza wrx.

the clio didn't show any improvement when given optimax or similar when compared to the cheaper option, but the gti and especially the wrx showed a significant improvment in bhp and torque....

their conclusion was that optimax and similar are better but only if your car is able to make full use of the extra octane.

thus i think that yes, the tsport should make better use of better fuel than your previous mini.

hope that helps.

[TheNissanMan]

Yup, as GRD states the better performance your car is capable of the more you notice a difference, ie a 1.0l Yaris won't notice anywhere near as much diffrence as a Supra TT.

[Twincam.GTi]

The following is of my own experience of running Shell optimax:

When they spoke of doing away with leaded fuel at most (but not all, contrary to what certain media hype said!) outlets I naturally thought I’d have to adjust the timing on my 1970’s MGB GT (and perhaps make it even more slower );as leaded fuel was around 97/98 octane and unleaded is around 95.

However Shell Optimax which is 98/99 and BP Ultimate which is 97 has eliminated the need for this, also I find that older cars infact go better on Shell optimax as the octane rating (98/99) is slightly higher. I also run my 1989 Corolla GTi on Shell optimax, as it just seems to run and ‘idle’ better.

Although I said older vehicles go better on unleaded Optimax, it’s not always the way. My friends restored classic 1940’s Bedford Army truck (yes, it IS petrol engined!) actual runs better on normal unleaded (95 octane), so much so he reckons it runs even better now than 15 previous years of running it on leaded fuel.

Some people have stated that unleaded fuel would cause valve seat regression in older cars, this hasn’t really been the case as to do this you would have to blast your old motor up a motorway at peak revs for a few thousand mile and doing this would wreck many an engine regardless.

I realise my 2p worth hasn’t really been applicable for modern cars but as said the above is from my own experience.

Finally there has been some talk that if your modern car does a lot of stop-starting round town etc that filling up with Optimax every so often might be a good idea as it burns/runs cleaner and so on presumes it's better at removing carbon deposits etc, that can cause problems at M.O.T Emission test time.

[Black Knight]

Some cars it's worth the extra for optimax/high octane fuels, others pointless.

I'll move back to twin cam's comments in a moment but I'll stick to modern cars at the moment.

To get the best power out of the burn you want to ignite the fuel mix before the piston reaches the top of it's stroke. This gives the flame time to propogate and is at it's maximum as the piton comes onto it's downward stroke (hence giving best power) unfortunately the high pressure and temperature is very conducive to knocking (where the mix explodes rather than burning and is highly destructive to the engine). With an ecu controlled engine there will be a knock sensor attached to the engine. When the engine is running the ecu will advance the timing to light the mix earlier and earlier until it starts to pick up knock from the knock sensor. When it hears that the ecu retards the timing. The engine will continually tune itself based on the knock level.

In the UK and most of europe the standard fuel is 95 RON. Hence on most ECU's they're set for running on 95RON. If you choose to run your car on 98RON fuel it probably isn't set up to take advantage of it. The ECU map just isn't designed to take advantage of it and advance the timing far enough for 98RON to be worth while.

This shows on the comment that GRD008 makes about the 5th gear test. The hatch backes make little or no improvement. The turbo'd nutter mobile performance car of the imprezza is set up to use it and hence shows big improvements.

Sometimes modifications can be made to an engine that promote knock earlier (for example increasing the charge of fuel into the cylinder) and in that case also using 98RON would be advantageous.

To Twin Cam's comments about older vehicles.

Older non-ecu'd vehicles are hand tuned to avoid knock. When you ttook it to a garage they'd manually set the timing to the maximum advance where the engine doesn't knock. This can be affected by weather/atmospheric/fuel/engine wear meaning it would have to be tuned fairly frequently. If you manually tune it to take advantage of the high octane fuel then it will make it run better. tuning that high can make it lumpy and rattly at low speeds though hence causing problems on some vehicles

In summary if you have a performance car (think subaru impreza's, Mitubishi Evo's, Porsches, BMW M's, Honda S2000's etc, nissan 350Z's) then it's probably worth it. Anything else will only get a marginal improvement if any

[mensa]

Some cars it's worth the extra for optimax/high octane fuels, others pointless.

I'll move back to twin cam's comments in a moment but I'll stick to modern cars at the moment.

To get the best power out of the burn you want to ignite the fuel mix before the piston reaches the top of it's stroke. This gives the flame time to propogate and is at it's maximum as the piton comes onto it's downward stroke (hence giving best power) unfortunately the high pressure and temperature is very conducive to knocking (where the mix explodes rather than burning and is highly destructive to the engine). With an ecu controlled engine there will be a knock sensor attached to the engine. When the engine is running the ecu will advance the timing to light the mix earlier and earlier until it starts to pick up knock from the knock sensor. When it hears that the ecu retards the timing. The engine will continually tune itself based on the knock level.

In the UK and most of europe the standard fuel is 95 RON. Hence on most ECU's they're set for running on 95RON. If you choose to run your car on 98RON fuel it probably isn't set up to take advantage of it. The ECU map just isn't designed to take advantage of it and advance the timing far enough for 98RON to be worth while.

This shows on the comment that GRD008 makes about the 5th gear test. The hatch backes make little or no improvement. The turbo'd nutter mobile performance car of the imprezza is set up to use it and hence shows big improvements.

Sometimes modifications can be made to an engine that promote knock earlier (for example increasing the charge of fuel into the cylinder) and in that case also using 98RON would be advantageous.

To Twin Cam's comments about older vehicles.

Older non-ecu'd vehicles are hand tuned to avoid knock. When you ttook it to a garage they'd manually set the timing to the maximum advance where the engine doesn't knock. This can be affected by weather/atmospheric/fuel/engine wear meaning it would have to be tuned fairly frequently. If you manually tune it to take advantage of the high octane fuel then it will make it run better. tuning that high can make it lumpy and rattly at low speeds though hence causing problems on some vehicles

In summary if you have a performance car (think subaru impreza's, Mitubishi Evo's, Porsches, BMW M's, Honda S2000's etc, nissan 350Z's) then it's probably worth it. Anything else will only get a marginal improvement if any

Are you saying that it's not worth using Optimax in a Corolla TS?

[nightrax]

l found that optimax makes a little diffrence compaired with normal fuel.

BT Ultimate - Seems to make the engine a bit smoother but thats about it.

The best fuel l have found for the T-Sport is Tesco's Super 99RON, l put a full tank in the car and !Removed! hell what a diffrence, the car is smoother and acceleration through the rev range is better and it has much more get up and go when you plant you right foot - hehe

[Black Knight]

Are you saying that it's not worth using Optimax in a Corolla TS?

Gut feeling, no. I don't think the ECU is set for it.

If anyone has any power/torque curves for it I'd be interested to see them though. Most people just get a placebo effect from using it.

[wilber]

normal running don't notice much difference butwhen it hits the valve lift there's a significant increase in kick. i always fill up with it our lass puts normal unleaded in it.(not compaining at least she puts some petrol in it )

[Johndcfc]

I think it makes a difference to economy and lift fastness.....

Here is my highly scientific reasoning for this:

with optimax and your foot down going 250mph the computer says 7-8MPG whereas sainsburys fuel goes down to 3MPG

[Black Knight]

with optimax and your foot down going 250mph the computer says 7-8MPG whereas sainsburys fuel goes down to 3MPG

How the **** have you modded that!

Strapped a Veyron to the back!

:D

[Johndcfc]

with optimax and your foot down going 250mph the computer says 7-8MPG whereas sainsburys fuel goes down to 3MPG

How the **** have you modded that!

Strapped a Veyron to the back!

:D

No, I've got 1,000,000 hamster wheels installed in the boot.

When all the hamsters are working at full pelt it gives me a 800bhp boost.

[Black Knight]

I thought those Hamster-chargers were still experimenntal?

[Blacksheep]

Hamsters are sooo old school, Tesco's are selling performance enhanced "white mice" man these boys now how to turn wheels not only that but you can get specific Toyota T Sport white mice that only come alive as lift engages, although make sure your Traction Control is switched on...

Getting back on subject I think it makes a difference maybe not in performance but mine certainly feels smoother could all be in the head though as I have no figures to prove or disprove...

[g3m xr]

havent read whole thread but i noticed a clear difference when i turned to tesco 99 ron in both my cts and my new scooby wrx

so much more responsive and smoother !

[vvtl-iboy]

havent read whole thread but i noticed a clear difference when i turned to tesco 99 ron in both my cts and my new scooby wrx

so much more responsive and smoother !

Shell are bringing out a replacement forthe Optimax called v something or other that has 99 ron. Not sure how much it will cost, but would like to see if that's any better than Optimax.

[rolley]

:D

They sure are. Just got an e-mail through from Shell Plus Points. V-power is 99 octane so that puts presure on tesco a bit. Hopefully we might see a little price war to bring the prices down. Fingers crossed!!!!

[scoobykilla]

I think the more power you have the more difference it makes, my gf has a corsa 1.6 16v sport and there is a little diffrence in performance between norm and super, i have an st205 moded to push 325bhp, the diffrence between the 2 fuels is unbelivable, totaly diffrent car on super.

[rolley]

I think the more power you have the more difference it makes, my gf has a corsa 1.6 16v sport and there is a little diffrence in performance between norm and super, i have an st205 moded to push 325bhp, the diffrence between the 2 fuels is unbelivable, totaly diffrent car on super.

Totally agree, found the CTS to be a bit flat in certain revs and you used to get a slight delay (flat spot) when your foot went down with normal 95 octane from Shell.

As I only ever fill up at Shell and used to fill up with 95 I took the decision one day to try opti and never went back. V-power will hopefully be even better...... :D

[Jones~32]

I have always run my ST205 on Optimax, and now V-Power