DrFolamour

Guys,

I am currently waiting for my RX8 to arrive in two weeks here in Switzerland. It will be a 231HP Cosmo, running with 95 Octane fuel, according to the owner's manual.

I've seen people here in the forum writing about 91 octane. I suppose they are american...

My questions are : should I go for 95 octane due to the cat. or go for 98 for xtra performance (as I do on my 6 years old Mondeo). Do we have in Europe xtra HP running on 95 ?

ChrisW

Americans use a slightly different rating system - I think their 91 octane is equivalent to 95 RON in Europe.

Actually, I'm surprised there hasn't been much investigation into whether higher octane gives better performance for the RX-8, especially with all the arguments there have been about the car's horsepower. A lot of people seem to think that higher octane has no benefits for rotaries, but do we know for sure that this is still true for the Renesis?

I have used 95 and 98 RON in my car and I couldn't detect any obvious difference in performance but it may just mean that the difference is fairly small.

WTF no turbo

I put in some 101 octane for the hell of it.No real noticeable difference really.

Roar 629

you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce octane in winter ) to obtain the most cost-effective fuel without loss of driveability.

Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realising that you have, could be expensive engine damage.

XDEEDUBBX

try vp racing 118 octane...i put it on my 43cc scooter and it was a totally different machine..but it will cost you...

Wildcard

Here in Australia we use RON not octane too. I've tried 91RON, 95RON and 98RON fuel in my RX-8 with no noticeable change in performance or economy between any of them. I'm sticking to 95 or 98 though purely for peace of mind because that's what the owners manual recommends.

takahashi

same here... I am trying the BP ultimate 98 RON simply think it is better than Shell Optimax 98 RON

sto16

Hello,

I recently used 94 octane (Canada) compared to 91 Octane and I gained 80km extra (50 miles i guess). Same driving method.

Simon.