Petro-Canada Ultra 94 or Shell 91 V-Power?
 

I've been using Petro-Canada Ultra 94 in my FD whenever I can. It seems to run fairly well.

Has anybody noticed a difference in engine wear or on the seals with ethanol-mix fuel vs. "pure" gasoline? I assume the RX-8 can handle some ethanol, but I'm not sure if the 13B-REW was designed to work well with the new gas.

I've only run Ultra 94 in my FD since the day I got her... Never tried any other rating.
Our cars love the higher octane. Typical turbocharged engines of the 90's. :)

Ive noticed that the V-Power tends to do a good job of creating a "safety barrier" and seems to have a pretty good performance.
But then again I get bribed over by shell giving air miles :lol:

I've used both in my racecar. I found that performance wise its a tossup, but I do get an extra lap every hour with the Shell 91 V-Power. There is more energy stored in gasoline versus ethanol, so burning straight gasoline (as long as you don't need the octane) actually has more potential energy per litre than a gasoline ethanol blend. In my SC Jag, I do notice more power with the 94 as the car doesn't go into the knock sensors as hard.

For the Cougar, I need at least 101 octane, I have used all kinds of race gases with all kinds of additives like ethanol, MMT, toluene, etc...., but the car runs best on the freakin' mondo expensive straight race gas you get from VP. This year I am going to try it using Ultra 94 and 2 bottles of Torco octane booster. This supposedly really works and boosts the anti-knock without adding all of the other rocket fuel stuff.

If you don't need the octane use the Shell. If you need the octane, then use the Ultra 94.

What mods have you done to the car? If it is still stock then I might try the lower grade but I'm sure many wouldn't. If you have modded the car I would only use 94.

not really a fan of the 94 octane i use to think it was better but they add so much crap to it. my FC always ran better in the 1/4 mile with the vpower. when I was running stock chipped ecu and AFC neo with 94 I noticed it tricks the o2 into thinking its running to rich and would run leaner and i'd have to add fuel up top , and i'd get a light sputter , i was only running the stock ignition system though at 17psi

I have a street ported 13B-REW with an A'PEXi Power FC and Greddy boost controller on stock sequential twins with some bolt-ons. The dealer quoted 325 HP, so I'm guessing the boost is about 12 psi max.

Dealers just make things up.

I run V-Power 91 in both my Speed3 and my FD. However I am planning on doing my fuel system and upping the boost in the FD this fall. At that point I'm switching to 94 to be safe.

-Geoff

I thought the minimum octane on the Speed3/6 is 93 Oct .... well at least in 2006 with the original ECU.

94 for both my Speed6 and FD.

No. 91

-Geoff

94 just for the safety margin...

There is no negative effects from ethanol. I wish we could get E85 up here.

thewird

I use to only put Ultra94 in my RX7, thinking the most expensive is best; highest octane prevents detonation.
But for my daily driver (Honda), I don't get any extra mileage from Ultra94 vs 91Vpower. I believe I get better mileage from Vpower, actually.
And because my RX7 is naturally aspirated, I sometimes switch to 87 octane, just to see if I can tell a difference.
When I'm cruising, I think 91V works better than 87 octane. But when I'm hammering it, the gas needle just drops, regardless.

I tried a tank of V-Power for the Mazda meet and cruise last Sunday. Mileage seemed to be pretty decent, considering the conditions, so I might save the Ultra 94 for high boost situations (e.g. track days).

Not all petro-canada's are the same. Petro-Canada stations that DO NOT have ultra 94 have 91 grade gasoline with no ethanol. Petro-Canada stations that DO have ultra 94 have 91 grade gas WITH ethanol. Ethanol is inferior to gasoline in terms of energy content by volume. A tank of pure 91 with no ethanol will get better mileage than a tank of e-blended 91 (if both were driven exactly the same).

That aside; I fill up my speed3 at Shell with 91 because Shell 91 is ethanol free, saving me from having to find the right Petro-Canada. Conversely I fill up my RX7 with Ultra94 (which has ethanol in it) purely because the car is so highly modified that it needs 94 octane.

Using 91 octane in an engine that only requires 87 only provides psycological benefits.

-Geoff

just stick with petro 94

You should only be running 87 octane in a NA rx7. Otherwise you are just making it harder for your engine to complete combustion due to a higher ignition point associated with higher octanes - basically it will ignite later. Plus its cheaper - if you want to go fast put a turbo on it.

And here I thought a higher octane would give me a more constant burn; a complete burn; a cleaner burn.

I never said higher octane would make me go faster. I figure if it burns more complete, I could cruise further on a tank of gas.

I guess I was wrong.

And I like buying cheap gas!!

Its not the higher octane thats giving you the extra mileage, its the purer gas of 91 v-power. If your car is N/A, it needs to be tuned to take advantage of the extra octane.

thewird

I ran 87 Octane in my S4 TII........

But it was also stock, and the manual said to run 87. Never had a problem.

I run V Power 91 in the car now that its modded. I don't like messing with BIO fuels. I try to avoid it in the diesel too when I can. If for some reason I need more octane than 91, I just buy actual pure racing fuel.

Don't ethanol attracts moisture and eats rubber seals/diagrams a lot quicker than pure gas?
If the car sits most of the time, won't that be bad?
Ethanol gas also has a 90 day expiry.

I don't think the 5-10% ethanol added to fuel is much to be concerned about.
I've only ran Ultra94 in my car and I've never had a problem with it during storage months. And that's without adding any "stabilizer" fuels either. She'll go through the winter months just fine.

I think this sort of thing tends to affect vehicles after you've let them sit for a few years. But during the winter months, I don't see anything happening to it.

I think I'll store mine with pure gasoline: E15 and Engines - Can Ethanol Damage my Engine - Popular Mechanics

Apologies for resurrecting an old thread, but I found some more info on ethanol here:

https://www.rx7club.com/alternative-...stant-1020965/

At this point, I'm still storing the FD with Shell 91. It costs less and based on my research, the gas should be fine for about 3 months. Now my curiosity is piqued by race gas:

Pro Racing Fuel |