I ran into a dispute on a local car tuner forum of fuel types.

Where I live, we can get a 91 octane fuel without ethanol or a 94 octane fuel blended with ethanol. The controversy is that ethanol blends can actually harm injectors and on older vehicles, can severely reduce gas milage. My question is if it's okay to use an ethanol blend on a stock fd. Currently, I use th 94 octane ethanol blend and haven't noticed any ill effects. Obviously gas milage isn't great but hey.. it's an FD. My philosophy behind that is I'd rather just use the higher octane to have the peace of mind that I'm doing everything I can to prevent detonation. However, if the ethanol blend is harmful in any way, I wouldn't be reluctant to opt for the 91 octane.

Another quick question, people from the afformentionned site are saying their vehicles run alot better on fuel from a certain gas station but run like crap on fuel from another. I don't fully understand what "run like crap" might mean. I thought maybe knocking but that's a pretty severe consequence for simply using a different brand of fuel. Would they maybe mean fuel economy / power / AFR wise (according to their tune)? Do any of you notice anything like this?

I tried using the search function as well as google as this topic seems like it would have been covered time and time again but I really didn't find a difinitive answer, only opinions. Input anyone?

 

If its a bone stock FD with no mods, just use Shell 91 which will give you the most bang for your buck (gas mileage and power). Putting 94 in serves no benefit except taking money out of your wallet and can actually decrease power. If its a modded/tuned FD, use 94 generally for the octane. I'm assuming we are talking about Petro 94 (old Sunoco).

The reason you will get better gas mileage out of SHELL 91 is because Shell 91 is pure gas. Since ethanol has less btu's per volume, any fuel mix using it will provide worse gas mileage. And also less power is possible unless your tuned for the higher octane that 94 provides. That is why on a bone stock FD putting 94 in your tank is just a waste of money as it provides no benefit. The whole reassurance thing is mute, if it was going to blow, it would blow on either fuel (keep in mind I'm referring to completely stock FD's).

Having said that, don't worry about damaging your fuel system in using ethanol based fuels. Don't believe everything you read on the internet. Take everything you read with a grain of salt.

On a side note with my RX-8 I have tested using both Shell 91 and Petro/Sunoco 94. What I learned using the Cobb Accessport was that when I used the 94, the ECU kept adding fuel via the fuel trims. When 91 was used, fuel would be subtracted via the fuel trims. About 2% each each both ways which is a 4% difference (according to the Cobb anyway). This just proved/emphasized the whole fuel mileage and btu per volume thing.

As for the run like crap, people generally exaggerate. I notice when I'm running 87 in the RX-8, that it will idle a little different. Basically not as smooth as it does with the 91 but otherwise runs fine. Most people probably wouldn't even notice the difference to be honest, I just have the habit of always paying attention to how a car idles, especially a rotary. That still doesn't stop me from using 87 in the winter since I don't drive the car hard anyway. It still pulls fine all the way to 9k even with the 87. Actually pulls harder due to the cold, the opening of the ports is much more pronounced, almost feels like the sequential twins transition.

thewird

 

1993 Owners Manual section 3 page 2
Canadian government mandates a minimum 5% ethanol content for total fuels produced.
Husky Mohawk is E10 for all fuels.
PetroCanada is E10-regular, E5-Mid, 0 Premium
Shell Premium should also be ethanol free like stated above.

I personally use only Petro Canada 91 or Shell 91 since they're both ethanol free and close to my place. If I was in a pinch I wouldn't worry about filling up on premium with ethanol.
Overall there is point buying Husky 94 on a stock tune and you'll end up losing gas mileage too.

 

^ Typo above sorry. should state 'Overall there is no point'.

 

Time for an update - apologies for the thread necro:

Ethanol-free gasoline was banned in Canada starting December 15, 2022. Ontario is now looking at forcing 15% ethanol by 2030.

I did a quick web search and it looks like about 98% of gasoline in the USA may also contain ethanol.

Short of extreme measures (like buying race gas), it is nearly impossible to find ethanol-free fuel for your rotary engine in Canada.

Generally, I would never mess around with fuel additives, but we are living in difficult times. Newer models like the RX-8 may be less affected by increasing ethanol content, but our FDs and older rotaries need to investigate how to deal with ethanol in gasoline, particularly cars with stock tunes and parts.

I looked up the viability of Lucas Safeguard Ethanol Fuel Conditioner - it seems to do the job, so I'm going to try it with my FD. I don't always agree with Project Farm's testing methods, but he's done good investigative work outside of the major corporations' marketing machines. I may also test Gold Eagle's STA-BIL In-Season Protection fuel system treatment (a rebranded 360° Protection ethanol fuel treatment).

I put Project Farm's fuel stabilizer test below as well, as many of us store our rotaries in the winter (often for 6 months or more in Canada) and another ethanol vid for fun (yes, those are his real teeth) - the comment section is the real gold.

Bonus: I might try Sylvania's headlight restoration kit on my hazed foglight lenses.

 

Don't overlook BG 44K, especially for storage. What I have done in the past when I lived in a cold climate is run the tank down to like an 1/8th of a tank, throw a can of BG 44k in there and take the car for a spin. This will leave a high concentration of the cleaner/conditioner in the fuel so when you park the car, the 44k is in all the lines, injectors etc. Then when its time to drive again, you can go top off with a fresh tank and be good to go. I've been using this stuff for 25 years and it does wonders. Its been my go-to for cleaning injectors in JDM engines that have been sitting for a while as well as my general upkeep in all my cars every 15K miles or so, more frequently in the fun cars because those don't get driven much at all.

 

Thanks, I'll look into BG 44K.

There's a lot of snake oil being sold re: fuel additives, but our FDs were never designed for 2026 fuels.

We may be in an intermediary period in gasoline technology - synthetic gasoline may become viable in 10 years or more, removing the ethanol question:

https://www.supercar-driver.com/blog...panic-just-yet

The gasoline question is a legal problem as well as a technological one. I think we, as classic car owners, will have to lobby to keep pure gasoline available - current events indicate that we need to address the gas and oil supply with better solutions.

 

If you on a standalone ecu, you will want to re-tune the fuel delivery for the new fuel density. You will need to bump up injection times a little bit. Once that is done, you should be ok as long as you are not storing the vehicle for long periods of time. Like you said, in the US most commercially available fuel is diluted with a minimum of 10% ethanol, and has been for years (Except for specific/rare ethanol free gas). There is also E15 and E85, more availability concentrated in the mid west areas. The biggest concern with the low ethanol blends (E10/E15) is that the two components attack each other as soon as they are blended at the refinery. Over time, the alcohol breaks down the fuel and it congeals and does other nasty stuff. This is typically not a big concern as you work through a tank of fuel quick enough for the degradation to be severe enough to cause issues. If you plan on long term storage, greater than 4-6 months, I would make sure the fuel tank is topped off, leaving as little space for condensation, and mix in some fuel stabilizer. This is more of an issue for small equipment/motors. I have switched to ethanol free fuel for all of my small engines like lawn mowers, trimmers, chain saws, etc. The ethanol blended fuel breaks down in the carburetor bowl and jets and congeals into a jelly puck.

 

California switched to E10 in the 90's, and nothing happens. it is 99% a non issue. you might notice a 1% decrease in mileage.
apparently it goes bad faster, but i've had cars pass smog with gas that was at least 5 years old, maybe more

 

Thanks, I've been able to start my car with some fairly long winter sitting intervals, but I'd rather not keep taking my chances.

As usual with these things, your mileage may vary - my FD has been sitting way too many months (and years) recently, so it's becoming a real issue for me.

 

let me put it another way, basically every FD in California ONLY ran on E10 the whole time, and we didn't seem to have any different results than anyone else

 

Excellent. I'd rather just run the gas normally and not use the additives, so I'll swap out the gas in the tank and see how things go.

 

Some forensic E85 analysis: