vafuncool

I noticed recently at a Mobil servo that they have a 6000 premium unleaded fuel. There's not much info about it on the Mobil web site, I only found the following:

"A premium unleaded petrol suitable for all cars. Some manufacturers of high performance vehicles do recommend use of a higher octane fuel such as Synergy 8000. Some pre-1986 cars may require use of an additive. Click here for information about the phaseout of Mobil LRP.

Was wondering if anyone has used it before in an 8?

Wildcard

I use 2000 regular unleaded but I think I am about the only one here who does! Still, I haven't put a drop of premium in my tank for over 12 months, and my car performs just as well as it did before. The only difference has been in my wallet.

OT a little, here is what Richard Paul said a while ago about octane:

Just stirring the pot a little....

timbo

I have always run premium unleaded (Ultimate), mainly because of the cleanliness of the fuel rather than octane. If someone can assure me there are plain unleaded without crap in it, I might try ... but after all, Mazda does say to use premium unleaded

tonym

Mazda Aus say to use PULP of 96 or greater in th manual and label on the fuel filler cover. How it may effect the warranty i you continually use <96 would be up for "discussion" if you had engine problems.

I use BP and they now only have 92 or 98 (Ultimate), other suppliers still provide 96 PULP. Shell Optimax is between 96 and 98 (they say average of 98), whereas BP have minimum of 98 for Ultimate. Makes little difference o me as my fuel is "pre-tax" cost on my lease

Tonym

RXE16T

I usually cycle between Shell Optimax, BP Ultimate or Mobil Synergy 8000, all of which are 98 octane and readily available around Sydney.

IMO, the BP Ultimate seems to give me the best fuel consumption and power increase (only marginal in both areas).

takahashi

Power increase.... nojooc.

You must have a sensitive butt :D

Oh BTW there is a BP station on the way to work (Pakenham) has BP Ultimate, BP Premium (95 Octane) and BP unleaded (91 octane). The best fuel economy is of course the Ultimate, but I tried on my Camry V6 to mix 1 part of Ultimate to 4 parts of unleaded, I get a less than 5% of difference in fuel consumption at the same speed and same road (over 220km of highway each day). I have not been brave enough to try that on my 8 though... I will never do that. HEHE :D

Also, what is the terminal gate price.?
http://www.bp.com.au/TGP/default.asp#

RXE16T

Maybe not a power increase, but definitely an improvement in responsiveness.

Wildcard

I don't want to start a pissing match here, but all I can say is that if you've never tried regular, your engine is not going to blow up from trying.

I filled up with premium last week for the first time in 12 months before I did the Putty road. I stand by the fact that my butt did not notice any difference, and believe me, I'm all about finding more power. I got more out of my custom intake mod.

It will be interesting to see what my engine looks like when it gets pulled apart to get ported and supercharged. Then I'll have no choice other than to be on premium anyway. Doh!

zoom zoom

rx8cited

I'll second that ......... I've got 15k+ miles on my car, and it's had regular unleaded (91 RON) since fill-up #2.

Here's what it says in the US 2004 Owner's Manual:
"Your Mazda will perform best with premium unleaded fuel {91 [ (R+M)/2 method] or above (96 RON or above)}.

You may use a regular unleaded fuel with Octane Rating from 87 to 90 (91 to 95 RON) but this will slightly reduce performance. Fuel with a rating lower than 87 octane (91 RON) could cause the emission control system to lose effectiveness. It could also cause engine knocking and serious engine damage."

Lock & Load

Great idea in getting ported and supercharged at the same time Dr phil will be bussy .

cheers
michael

timbo

Are we not dealing with a 'learning' ECU here? And isn't fuel octane one of the factors it learns about and calibrates against? Therefore, might not the fact Wildcard feels no different from his premium fill stem from the fact it has 'learnt' he uses regular unleaded. I'd love to know the answer to this question, and more about 'learning' ECUs, because I'm damn sure mine has learnt never to use less than 10L/100k no matter how hard I try on a trip

MaRX8

I'll just add what I've experienced. I've added Regular Unleaded 87 Octane to my car, and I actually get better gas mileage with the lower octane gas. I've done this experiment a # of times, I'll switch between 91 Premium and 87 Regular. Everytime I get more mileage from the lower octane gas. I've gone 300 miles on 1 tank of Regular where I usally get 240 to 250 on Premium. This is on a long distance drive without much stopping.. So that's a big enough difference to notice. But because Mazda recommends Premium. I usally alternate tanks, between Premium and Regular, with every other fill-up. Try it, it certianly won't hurt your car, and you'll be surprised when you actually get better milage...

skc

I usually fill up at Caltex and Mobil. Caltex say the premium contains 98 ron fuel, the Mobil just says premium unleaded therefore I am unsure whether it is 95 or 98 Ron.

However, I have had some concerns about premium mainly concerning the additives in the fuel.

The Rx 8 manual distinctly advises against the use of fuel additives. So using premium fuels which contains additives goes against this recommendation. This seem to leave a build up of deposits.

My concern with switching to regular unleaded is that if you encounter a poorbatch of fuel than you will suffer engine knocking and possible engine damage...I think Hymee reported some problem with this at some stage.

Therefore what I have to decide is which of these fuels will cause the least long term damage.

May be the option is to alternate between these fuels.

skc

Wildcard

As far as the "learning ECU" concept goes, I don't believe the ECU can measure or knows what octane fuel you are using. How could it??

Instead I understand that the engine has a "knock" sensor in it or some way of detecting detonation (regardless of what octane fuel you are running) and it retards fuel/timing/whatever to stop knocking.

So no learning required. Also, it supposedly only takes 10-15min for the ECU to learn a change (new exhaust/intake etc) so it should be happy with your new fuel before the needle has even left the stop.

Hymee

iTrader: (1)

I think Wildcard summed up "learning" and knock sensors pretty well. He is learning very well too

Skc - they don't have 98 RON Mobil here in BNE yet, AFAIK. And I thought I banned everyone from using Caltex Hehehehe.

I'm positive I get less mileage on (regular) ULP 91 RON compared to BP Ultimate.

Nojooc: If it isn't making any more power, then what is it that gives the extra "responsiveness"?

Cheers,
Hymee.

EDIT - I have had knocking /pinging on my car and Wildcards car with the TSI controller installed. On both occasions, the TSI unit had a tune in it that was not optimum for the flash in the vehicle's PCM. And I guess that on both occasions there was ULP in the tank.

RXE16T

F***ed if I know!
Maybe it is increasing the power? :p

Hymee

iTrader: (1)

Well let me explain a little physics! The torque is the force that is pusing the car along. Power is a sort of like a measure of how quickly that force can be kept up. (Think of a steam traction engine - makes a ton of "force", but it cant do it very quickly). So if the car is more responsive, it is making a little more power. Generally, these little feelings of "it feels more responsive" is probably what we feel with a very low kW power increase. When you really start to "feel" more power with the but dyno, we would be looking at 10kW or thereabouts.

But there are so many senory inputs when driving a car in addition to the nerve that connects the sphinkter to the brain.

Cheers,
Hymee.

RXE16T

So maybe it is making marginally more power........ but not enough for the butt dyno to tingle.

Hymee

iTrader: (1)

Well done!

Cheers,
Hymee.

sinkas

Hi all,

While Im not sure tis is really an appropriate post,

Most of the Mazda Rotaries early racing success was achieved on very low octane fuel, ( specially prepared below 80 RON).
While thsi may not be much of an indicator for useof low octane fules in the RX8, its something worth following up.
As for the fuel economy benefits of the 98 Ron fuels, I think its probably more to do with the clean fuel density than the octane. I think BP ULP is pretty clean. Here in WA, most other retailer of fuel now have links with shopping chains, adn are deliveing very average fuels.

Cheers

Case

Gibbo

I have always used either Optimax or more recently BP Ultimate, after reading this post I tried 91 octane. I then proceded to dive my car harder than usual. I did not notice any pinging, nor any decrease in power or response. I will try a second tank on regular for my next fill up too. I run the piggy back ECU TSI with no issues.

The price of petrol is not my issue, however I figure why **** $6 up against the wall at every fill up if there is no noticable difference.

Hymee

iTrader: (1)

Don't forget the older RE's were lower compression than the rensesis. And when we start talking forced induction, the higher octane rating fuel will give you a higher marging of saftey.

Cheers,
Hymee.

takahashi

I am so confused ....

Is it alright to compare Shell Optimax in Melbourne and Sydney. Surely they are from different plant right?

Have anyone seen any research done regarding quality of fuel. I am sure there will be something like the Choice magazine compare different bland of fuel in different state.

Now we all speculate and listen to what other drivers said but I have yet seen any objective research data on this. It is not hard to collect sample, test purity in a scientific lab right? ... any response?? labrat?? :p

labrat

Taka, unfortunately we don't test fuels. We make scientific instrumentation geared to a very specific sort of test technique called titration, which is not applicable in the sort of fuel testing I think you mean. All petrols will differ according to the composition of the crude oils from which they are distilled. That's the first thing, but the refiners also have the ability to blend distillates, as well as add components such as aromatics (toluene & xylene) to make up any deficiencies in the blend, particularly with regard to octane rating. Then there are the additives to keep fuel injectors clean and other sorts of stuff they put in.

I think you may be right in assuming that an Ultimate or Optimax in one city mightn't be exactly the same as in another, but the refineries do work hard to maintain a standard specification by appropriate blending. The analytical methods used in the petroleum refineries are very strictly followed, and the same methods (eg, ASTM) are used around the world.

I'm not sure that imported fuels are necessarily inferior. You'd have to know exactly where the fuel comes from to make those sorts of comments. For instance, the refineries in Singapore are reported to be more modern than those in Australia. Certainly, I would have some doubts about some independents. There were stories about some Sydney indies selling almost pure toluene. Great for octane rating sure, but pure toluene burns hot, and wouldn't do your valves much good I would imagine.

I buy my fuel from Shell/Coles - currently, I'm getting 8c/L discount with their summer promotion.

Talking about dirty petroleum products, I think the most dishonest ad. I saw was Peter Brock extolling the virtues of a synthetic oil, and rubbishing mineral oils because they came from the ground and thus contained "dirt". What crap! Mineral oils are distilled, just like the lighter fuel fractions. Any solid crud is left behind in the still. Synthetics might offer better performance, but it's not due to natural oils being dirty. Please don't get me started on all the pseudo-science snake oil stuff being peddled out there in ad. land. Taka, you might like to comment on "detox" diets.

sco

That's if you had valves. :p

Great post labrat.