Super

Chadley · Post by **Chadley** » February 14th, 2005, 2:27 am

really

mitmaks · Post by **mitmaks** » February 14th, 2005, 8:41 pm

if you can afford premium it wont hurt it

Thunderstorm · Post by **Thunderstorm** » February 15th, 2005, 6:26 pm

Re: your question about the virtues of using Optimax fuel;

I used to own a 1988 Honda Accord 2.0-16i DOHC PGM-Fi.
This Wolf in Sheeps skin was a powerful beast in disguise.
It's Twin Cam engine delivered 160bhp. It was rather lethal in the wrong hands.
The previous owner used only Regular Unleaded - however, I noticed the filler cap lid clearly "ordered" it to be filled with 98 RON petrol only. This of course was Super Unleaded or Optimax - if you like.

The first time I filled it with Optimax, the difference became rather obvious almost immediately.
There WAS a distinct increase in performance, and the engine operated a lot smoother than previously.

Overtaking was way faster, and I had great fun out accelerating smug drivers in their posh cars who mistook the old Honda for a clapped out mini-cab. Engine RPM response was instantaneous.
Optimax made a powerful engine even more potent.

HOWEVER....I used Optimax (which i subsequently dubbed "Rocket Fuel")with its 97 or is it 98 RON chemistry only because Honda "insisted" that was what the JDM DOHC had to use.
And by golly, it made a helluva difference on that car.

On 2 occasions I was forced to use Regular petrol in the absence of Super Unleaded - and I noticed the drop in performance.

If Mazda themselves had specified 97 / 98 RON Super Unleaded for the V6 engines, then one could feel safe totally utilising it.
It does work. There is a difference.
I swear by Optimax through past experience.

I do not know how the MX-3 GS V6 & RS DOHC engines would react to being regularly run on Optimax type fuels long term.
Would the ECU's compensate for the difference in fuels?
Had Mazda already considered the possibilty that drivers might fill up with this stuff and made the engines tough enough to handle the extra Oomph that the petrol delivers?

I don't know, but would like to too.
Perhaps I should RTFM first, then decide.
Ironically, one of the reasons I bought the MX-3 RS was because it ran on Regular. I'd had enough of paying through the nose for Optimax type fuels.
Maybe Mazda made these engines with economy in mind - save money, buying only Regular Petrol, perhaps the powerplants can take Optimax too as an option - and one can enjoy a small increase in overall performance like i did in my old Honda.
I suspect both these engines would benefit from the use of Optimax.

It would be nice to hear some testimony from anyone who has used (or is using Super Unleaded Petrol in their MX-3.

Pardon the rambling and digressing.

jschrauwen · Post by **jschrauwen** » February 15th, 2005, 11:13 pm

I've been using Sunoco 94 since the day I got the MX, 10 years ago. I don't believe it hurt the engine in any way and I do notice a performance lag when I don't use it. Regular plug checks confirms the quality of the burn. In an area where regular gas is 87 octane and I believe that that's what's called for for the NA spec MX's. 94 Octane is the highest we can get unless we use an octane additive, or happen to stumble on to some Avgas ( something my Ducati just loves). At any rate I will continue using the higher than prescribed octane now that I have just done the KLZE conversion. Cheers.

Chadley · Post by **Chadley** » February 16th, 2005, 4:52 am

getting

rasheedn · Post by **rasheedn** » February 16th, 2005, 7:11 am

i got a jap mx3

would it make any difference if i used the more expencive one then??

optimax one ? i just use the cheapest i can find

jschrauwen · Post by **jschrauwen** » February 16th, 2005, 10:43 pm

To an obvious limit though, I always believed the higher the octane the hotter the burn = cleaner burn = less fowling = better performance. Unless you're constantly on the highway (sorry, motorway), where you're able to maintain a reasonable period of sustained higher speed, then you can get away with a lower octane because your engine's running hot enough, hard enough and long enough to prevent significant fowling. Mine is about half and half, city/highway, so I consistantly use the higher octane gas. Always had good looking (colour) plugs , so I know I'm doing the right thing. Oh yah, higher octane = higher cost petrol, but also = less tune up requirements and plug replacements = a much bigger savings. IMO

snellgrove · Post by **snellgrove** » February 22nd, 2005, 5:32 pm

I've got 95RON cack in mine at the moment, and its getting pretty poor fuel-economy..

might give 98RON a go next time, and whack a dosage of Redex in there too (just to give it a nice clean out.. ) and see how it goes, i'll let you know any results.

not expecting the fuel-economy to rise dramatically, or much at all.. but if it makes it more torquey thats good, coz I got beaten out of some traffic lights by a 90bhp Golf TDi today.. (damn you peak-torque being at 5000rpm!) was very embarassing..

Chadley · Post by **Chadley** » February 22nd, 2005, 6:24 pm

bored

IanL · Post by **IanL** » February 23rd, 2005, 4:01 am

The FACT is that the higher octane fuel develops no more power. It is, put simply, formulated to prevent pre-ignition at higher compression.

However, if you use too low an octane (compared to that for which the engine was designed), the ECU will retard the ignition to prevent pre-ignition (actually it will advance it less), which will reduce the power.

The MX-3 V6 engine (K8D) is designed to use 91 RON. So 95 is fine, and 98 is money down the drain. The JDM imports (K8ZE) are higher compression, and probably need 98 RON.

If your engine is in bad shape (e.g. lots of carbon deposits in the combustion chambers), you may get benefit from higher octane, as the carbon both raises the CR and increases the tendency to pre-ignition.

US and Canadian drivers please note your Octane numbers are not RON, they are (R+M)/2, and are about 5 lower for the same fuel.

snellgrove · Post by **snellgrove** » February 23rd, 2005, 3:55 pm

yeah, higher octanes dont develop more power, but the engine can get more power out of higher octanes being there, as you say.. ignition advance.

gonna give mine super or opti next tank, and redex.. it may have carbon deposits, (previous owner did lots of gentle town driving and stuff! ) and give it a blasting out.. clean it out nicely

Thunderstorm · Post by **Thunderstorm** » February 26th, 2005, 7:07 pm

Decided to do a little experiment with Shell Optimax and "Blackbird".

I have been keeping a record of my fuel consumption since I got my MX-3. This evening, having emptied my tank as far as I dared (it doesn't have a fuel reserve warning gauge

) I pulled into Shell petrol station and filled "Blackbird" to the max with Shell Optimax Fuel.

Visions of any engine failure or rough running were immediately dispelled as I fired the 1.6i DOHC to life, and left it idling while I entered the latest fuel consumption figures in my HP iPAQ.

There were of course no immediate obvious differences to my MX-3's performance when I got initially moving again.
I am trying to maintain a "sceptic" view of what Optimax might achieve in my MX-3, despite having enjoyed its performance in an old 3rd Generation Honda Accord that also had a DOHC JDM 160HP engine that was designed to specifically use 98RON fuel.

However, after cruising around in traffic for a while, I did make the following observations;

The engine was running marginally smoother than it was before.
(There was LESS vibration at idle, particularly after dark when almost all ancilliaries are in use - Heater, Wipers, Headlights & Stereo - normally when under electrical load, the engine does vibrate much more)

The engine was running quieter that it was before.
(OK, I didn't have a Decibel measurement device running, but there are roads I normally barrel up and down regularly with disturbing monotony. I know exactly how much noise I get when barrelling up the A406 Hanger Lane for example. This time, it was way smoother and quieter - I'm sure that was not in my mind)

Smoother Crawling Control in congested traffic.
(I'll explain - my MX-3 tends to be rather very sensitive to my accelerator foot in traffic. There is a jerk when you try to increase your crawling speed, and a jerk when you take your foot off the accelerator. It's not exactly annoying - just makes you look like an incompetent driver. That phenomenon seems to have all but disappeared curiously. I was able to crawl very smoothly in traffic).

Mysterious Flat Spot during 1st Gear acceleration seems to have disappeared.
(Has anyone else with the MX-3 RS experienced THAT "millisecond" flat spot? I am assuming it is a design fault with the 1.6i DOHC. Only get it in 1st Gear, when accelerating purposefully, otherwise "Blackbird" normally pulls quite satisfyingly to whatever highspeed I want without repeating it through the gear changes. Now it's gone. It was there before I pulled into the petrol station).

The car seems to "go" slightly better than it did before.
I was actually expecting the worst from Optimax, because I can find no reference stating that my MX-3 would be happy on 98RON.
I had visions of it choking on the stuff, even though science dispels that possibility.

I have about 10.8 days before my next fill up - according to my PDA, so I intend to observe any strange things that may - or may not occur for the duration that I am running on Optimax.

If anything I wrote above is in my imagination, you will hear from me.
I intend to give an unbiased report about real-time use of Shell Optimax in a 1998 Mazda MX-3 RS.

Stay tuned.

snellgrove · Post by **snellgrove** » February 27th, 2005, 4:56 am

Thunderstorm wrote: Smoother Crawling Control in congested traffic.
(I'll explain - my MX-3 tends to be rather very sensitive to my accelerator foot in traffic. There is a jerk when you try to increase your crawling speed, and a jerk when you take your foot off the accelerator. It's not exactly annoying - just makes you look like an incompetent driver. That phenomenon seems to have all but disappeared curiously. I was able to crawl very smoothly in traffic).

OH MY GAWWWSH!

my car is awful at this, it kangaroos and bounces and is so annoying in traffic, as you say..when you come off the throttle, or on to the throttle the car zooooooms away, or engine brakes VERY hard.. and its not smooth at all... right, thats it... tank of Opti is going in later today!!! I've done nearly 190 miles and the gauge is right down at the bottom.. to the point where its getting scary

snellgrove · Post by **snellgrove** » March 3rd, 2005, 3:55 pm

bugger, mines got Optimax in it now, and a treatment of Redex.. but its still bouncing like a b---- in 1st gear

its better, but not gone completely.. things I most notice are:

going on the throttle in 1st gear, with very minimal throttle input, the car jumps into life from no-throttle ..and races away very powerfully.. its like a very sensitive throttle (which I like) but the car doesnt seem to know how to do slow acceleration ?!?! so it really sucks around town.. I've been experimenting today when in traffic, like moving my foot what feels like tiny millimetres... like really slow movements, slowly adding more and more throttle, VERY GENTLY... but it still does it.

coming off the throttle, VERY SLOWLY AND GENTLY.. the car keeps moving forward as normal.... until your practically off the throttle, then WHAM.. a sudden and almost violent off-the-throttle feeling as it engine-brakes VERY FAST... (1st gear) its like putting the brakes on!! the revs drop off so fast

if you come off the throttle quickly, I find you get that almost violent snap off the throttle, to engine braking.. but it does it too quickly for itself almost, and gets itself stuck bouncing along and kangarooing very unsmoothly, until you apply throttle to calm it down.

it'll happily kangaroo all day along the road in 1st.. without any throttle input once you set it up doing that by coming off the throttle too fast.

anything wrong with the car, or is it me somehow being too rough with the throttle... I dont think its me, I'm being so very gentle to it throttle wise round town when using 1st gear in traffic

DJ · Post by DJ » March 3rd, 2005, 4:00 pm

I have the V6 and run 91 octane (87, 89, 91 are my options here) since the day it was made. The manual says to use 91 and thats what the original owner went by.