What grade gas do you use.
 

I have been using 87 grade for over 3+ years with no issues. 94k miles.

Anyone else use the low grade stuff? Figure I saved about $2500 in gas cost so far.

I use 93 octane, but I buy the $1 gas station coffee which saves me $3 over dunkin dounuts so it's kind of a wash.

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93. Your car is probably pulling timing on 87, but it probably won't hurt anything. The engineers probably accounted for at least some amount of neglect.

91 because there's no 93 out here.

They did. That is why 93 is recommended but 91 is REQURED. False economy if it eventually screws up the engine. Think how much could be saved if you never changed your oil!
Next post will probably be "How can I get more power"?

premium. the manual says it will run on regular, but i noticed pinging occasionally while doing so, it's just not worth the potential hassle.

Fearing moving back to CA for a multitude of reasons, the worst (after state income tax of course) is the unavailability of 93 octane pump gas :mad0259:

91 here in CA :D

E95, listed as 105 octane, 3.10/gal. Good stuff.

92 because that's what premium is local to the Seattle area. I haven't seen 93 around here although I am aware it's the recommended grade. When I did my road trip to Minnesota, I encountered a few scenarios where I was stuck with 87 or even fucking 85 because I was out in the middle of nowhere in Montana, on the fuel light, and had to stop at some local ma and pa gas station in a town with a population of like 200. Luckily I carried a gallon of 92 with me that I mixed with a few gallons of 85 to make ~87. Got back into civilization shortly after and found some 93.

I've never found any but I've been wanting to try 105, how does it run? You don't need a tune for that right?

No it doesn't it says 91 which is still premium.


I don't think the OP understands what the numbers mean and feels that it is just a quality thing. It is not.

People suck.

Costco 93

Needs a tune for ethanol, using the OFT. Surprisingly strong running, and probably how it shoulda/coulda come from the factory.

My understanding may be imperfect, but the main affect low octane gas has is that if you ignite too early, it creates too high pressure near the cylinder walls, resulting in detonation. The Subaru ECU good at protecting the engine from this by pulling timing. The result is lower efficiency and power. My understanding is that the factory tune is borderline for not pulling timing with 91. It will pull timing with 87.

I guess it's questionable whether it can pull enough or whether 87 also introduces pre-ignition detonation. I guess someone could log some driving with 87, but anyone who can do that probably doesn't want to (including me lol).

Huh, it was my understanding that most high compression engines could run on 105 octane race fuel no problem. Am I perhaps thinking of a non-ethanol 105 octane?

93, since that's what the manual recommends and its available at the gas station near my house. :iono:

I'd imagine there's an upper RPM limit somewhere below redline where there's just not enough time left for the ECU to pull timing enough for 87. Not that anyone would be particularly eager to find where that is.

Your understanding is correct. However, some gas stations are not actually giving you the octane that is rated on the pumps. Stations with high turnover will usually be there but since the octane levels drop with age you can be at risk if using rated 87. It could actually be 82 or 84 and since the difference between the small changes in numbers is significate that is serious. The chance of serious pre ignition in a high compression engine increases. Will it pull timing in time is anybody's guess but you most certainly have some bad knock while it does. Could possibly (probably?) use it for the life of the car and never have an issue or you could blow the engine up from one tank of bad gas. I have had to put 87 in a couple of times and it is not big deal but it is not a risk I would accept on an ongoing basis just to save a couple of hundred bucks a year. I seriously question the claimed savings of $2,500 since you would have to go through a shitload of fuel. Ironically you would get worse mileage running the 87 anyway so any savings you think you are getting may be null.




Gonna say something I never do but...
If saving money by using the wrong fuel is that important than people need to be looking at other cars.

They will run on it but it will serve zero advantage unless tuned to take advantage of it. Higher octane does not mean "better" burning or higher quality. In fact it does the exact opposite as far as the burning part goes.

I get knock correction on 91, would never run anything less. I run on E85 most of the time now but changed during this last "cold snap" when it was hard to start in 30F temps. Plus I have to drive 15-20 min away to get it so is a hassle to begin with, but worth it for my engine to run better.

ethanol has different flow requirements then regular fuel so it requires a tune.

Makes sense, thanks.

Figuring 30mpg to be nice it's a savings of $600-650 based on the normal $0.20 savings from premium to 87

Well they we go then.

93 unless I find non ethanol gas then I use it, I've never seen it over 91.

93 Sunoco...

Why non ethanol?

There are places here and there where I live where you can get a variety of different race fuel octane levels from 98 to about 110. You won't notice any difference in your street car, except maybe an increase in acceleration due to the weight loss in your wallet.

Well, what if he drives downhill to work, both ways?

Non-ethanol gas has anywhere from 15-20% more energy than typical ethanol gas. This is completely separate from the Octane ratings. The Octane ratings is more closely related to the ignition timing and running too low an Octane will result in the engine knocking. Where I live at 7000 foot elevation in Colorado, the lower oxygen content in the atmosphere allows for lower Octane without getting the engine knocking...so typical regular gas is 85 rather than 87, premium is 91 vs 93. Modern vehicles are designed for the crappy ethanol gasoline, so there won't be damage to them and you may not see much change in performance. I've only put premium in my recently acquired FR-S, so I couldn't tell you anything about my experience with running it on regular Octane gasoline. I do have a 2010 Goldwing and my gas mileage on that is a minimum of 20% better when running it on non-ethanol gas at the same Octane. I also have a 2017 Power Wagon and haven't noticed any difference between 91 Octane ethanol gasoline and 87 Octane non-ethanol gasoline--the price is about the same here between the two.


An additional effect of driving at 7000 feet is a roughly 20% loss of horsepower for a naturally aspirated engine. A turbocharger does better at altitude than a supercharger, but it is what it is.


Two cycle yard equipment really prefers non-ethanol gasoline.

Correct. To run E85 you need a specific ethanol tune. The downside is 14MPG.

Ethanol though, has an effective octane rating of 160, and Methanol 180 through a DI system.
It has a very high latent heat of evaporation, and the benefits of running it far outweigh loss of energy. So much so that you will pass MBT before you start knocking on E85. If you can tune for it, it's great.
Your two stroke yard equipment is assembled with seals that don't stand up to the dryness of the alcohols. That's all.

91 in CA all the time.

Is that boosted?

I guess it’s kind of an experiment. I’ve had premium gas cars for the last 20 years as my personal vehicle. I keep daily drivers for a while. My last car I had for 13 years before I traded it in. I used 87 in it for the last 6 years without issue before trading it in.

Not sure where you live where it’s only 0.20 difference between premium and 87. It’s between 0.60 to 0.80 per gallon difference where I live.

No. I may be an agressive driver, since the front of the 17 is so aggressive. I think it was you who said you should drive either hard on the gas or hard on the brakes. Its more fun that way!

Wow, that is what I average with E85 with JRSC, bigger injectors and pump at 310 HP.

I did manage to get 45mpg coming home from Reno in my MR2. Went 85 in neutral the entire way down the mountain.

Holy hell. I never got worse the 17mpg on e85. And that was the first tank where I smashed the throttle everywhere. (Not counting on track lol)

Do you have any data from your experiment besides the car didn't die while you still had it? Like timing, MPG, knock correction, etc?

I'm in CA. if there is more then 0.15 between each grade it's a rip off out here. That's crazy it jumps so high

Provide your car is designed for it...it will eat up a lot of the older, classic cars--same issue with the seals and such, as you mentioned. We have some E85 here, although I think in general terms when I use the term ethanol gasoline as that gasoline that is commonplace and has no more than 10% ethanol added to the mix. When I first moved to Colorado in 2005, there were quite a few places that had pure gasoline...then the numbers started to dwindle. I think we were down to one single place in town, but a three more places have opened in the past year or so. The federal gas mpg testing still uses pure gas...find this kind of funny as it has been the government mandates and subsidies that have pushed the ethanol additions over the years.

When we used to do no class "fun run" days at the strip a couple of us with high compression (by the standards then) builds would run 100 in our street cars. We would fuel up at home (from cans) and spend about two hours tuning for it. When I say tuning I mean oldschool tuning of the carb, timing, dwell, plug gap etc with a screwdriver and wrench since computers still fill whole rooms and a laptop was a dance you got at certain clubs. After a couple of runs the noobs would ask us what we were burning and run out and buy a can or two. They would just dump it in and go for it. They could never figure out why they were never any faster.
Would have run it all the time but it cost about an hour's pay a gallon.