The Test

[Fidgits]

Recently, it was claimed that running the IS on Super Unleaded didn't work out any more expensive than running it on normal Unleaded. Due to the higher octane burning less fuel or something..

Now, I have decided to conduct a little test to prove this theory, I am going to let my car run as empty as i can, then fill up with Super. I will then reset the ECU, and run it for about 2 weeks.

Then in October, I will be doing a lot of 'known' journeys, to which i know approximatly how much fuel is used, and the cost of these journeys.

Now it may not be scientific, but I think I will get a reasonable idea to whether running the car on super costs the same as normal unleaded...

I will let you know

[ColinBarber]

Are you going to use Optimax or just Super?

[jamessutton72]

I’ll be interested in that, as I’m only getting 280 miles per tank.

Sorry, but can you tell me what the ECU does and how do you reset it?

[Fidgits]

Erm.. I was thinking just Super.. its easier to obtain, and depending on results, i can always move up to Optimax..

There is a thread somewhere here that explains how to reset the ECU

[Steve]

i dont think you will need to reset the ECU... I enquired to an enginner about this who works on performance cars and claims the ECU will not affect it

also dpends on your driving habits too.. if you did the same motorway trip every day you would probably get a better accurate result.

Some days i am heavy footed.. some days i drive slow.

[Fidgits]

Well Steve, thats my plan, in the aquamist thread, Mark (TDi) said this would work, and the journeys i will be doing are home -> heathrow, a route I know very well on compsumption and price.. and I will drive as normal to compare the results..

[ColinBarber]

Sorry, but can you tell me what the ECU does and how do you reset it?

The engine ECU controls the fuelling and ignition of the car based on a pre-programmed map and various sensors around the car (air temp, engine temp, exhaust sensors etc. etc). Higher RON fuel allows the ignition timing to be advanced which gives more power. Too much though and the engine will knock (pink) which will damage it. By using a knock sensor the ECU will retard the timing to the correct level.

If you put in higher RON fuel the ECU will not know this and by default will only try and advance the timing infrequently. By resetting the ECU all data is lost and therefore it has to relearn the correct settings. It starts off by using very conservative settings but will increase the settings at a faster rate than normal. So after a tank full of fast driving the ECU should be giving you the maximum performance.

You reset the ECU by removing its power. This can be done via its fuse, if it has one, but the definite way is to disconnect the Battery. It should only need to be done for a minute but as it is difficult to tell if the ECU has been reset it is recommended that you leave it off for 5 minutes to be sure. Also you need to discharge any power being held within the electronic circuits, which may still provide the ECU which enough power to keep its memory, by trying to draw some power by turning on the lights, using the horn or pressing the brake pedal.

[Bobski]

Well, ive been running on optimax for 2 months now.

At first i didnt see any difference (fist3 fillups), still got between 280 and 320 miles per tank.

From the trip up and back to JAE + a gatwick trip returned me 420 miles on 1 tank, and since then i seam to be getting 320 - 360 a tank.

[Loz]

might try the remove fuse option on my ECU as have 420 mile trip tomorrow... and just topped up with optimax.

I am pretty sure I can feel the difference between optimax and 95 ron if I do more than 2 tanks of either it changes the way he car drives. Also if I use the nos then after for a while it tries to hang onto gears for longer and revs really freely at the toop end. like a residual effect cos its anticipating a good caning!

wonder to what degree placebo effect takes place?

[NigeSt]

wonder to what degree placebo effect takes place?

Try giving your car a wash and polish, mine always runs faster and smoother afterwards B)

Seriously, I'm grateful for 380+ miles out of a tank, and I always try and fill up with Optimax, though I rarely manage a 'pure' tank.

Wish they'd fit larger tanks, just like Loz needs larger cylinders

Nige

[kev dood]

Does the IS200 have a knock sensor (not all cars do)?

So if its been run say on normal unleaded for ages, and then switched to Optimax, its better to reset the ecu too so its senses the change quicker?

If you don't it will still adjust though, via the sensor. I guess it will take longer to get full benefit. if so then by how much?

[ColinBarber]

Don't have a wiring diagram for the IS200 but I would be very suprised if it didn't. Possible has more than one.

[phunt]

I started using Optimax about a week ago but i havnt reset the ECU yet,im going to do it tommorow when i fit my bodykit but i was wondering if the stereo has a security code b4 i disconnect the Battery because i cant seem to find one in the documentation.

[UKPulse]

I regularly get 350 miles to a tankful, and got just over 400 miles on a tankful when going to JAE and back. My 2002 IS200SE Auto Nav also used to do at least 350 miles to a tank. Getting just 280 miles seems really low :o