Was doing some reading on JM Automotive's website after Grimmspeed posted a video about visiting there and saw this excerpt from their dyno checklist page: "Recommended not to have 91 non oxy or non ethanol. This is bad for turbocharged engines and is basically 87 octane in real life testing. We will tune your car on that fuel and you will make substantially less hp. If you decide to come back with a better fuel you will have to pay for a tune adjustment (dyno hourly rate)." At my wife's work, she carries 91 octane non-oxy (which is what I usually fill my car up with) and no option for 91 with ethanol. I've read conflicting information from some research after reading the excerpt on JMA. I am on the stock tune and basically stock in general and just curious if this fuel is harmful to my car/bad for performance or should it not be a big deal to use?
It basically is just like they say it is. I'm not gonna sit here and say I'm an expert by any stretch of the imagination but it makes sense. From what I've read and understand the ethanol kind of acts as a "buffer/cushion" against detonation and knock, which is a big deal on turbo cars. Essentially, the higher the ethanol content the more timing and boost you can run, thus the more power you can make. Hence why so many people are switching to E85 when possible. Look at JM's Dyno graphs when they tune somebody's car on 91 (10% ethanol) vs E85. The hp/torque number changes are pretty significant and that's just from changing the ethanol content. But running E85 also requires a decent amount more fuel in order to operate properly (I don't remember the estimated percentage or the exact scientific reasoning), this being the reason you need a bigger fuel pump and injectors. TL, DR. If you put 91 non oxy in your car on accident or because it's literally the only thing you can find, you'll be "fine" as long as you're not trying to drive it like normal (essentially just stay out of boost until you can refill with ethanol blended fuel). But long term it's definitely not the safest decision and most likely could do some sort of damage I'd think if you were pounding the car in boost all the time. Not to mention you're (usually) paying top dollar for non oxy premium and getting zero benefit. Again, this is just me repeating things I've read online over the years. In my own experience, I distinctly remember putting 91 non oxy in my car on purpose once several years ago thinking "well it has to be better, right?" I swear I could feel a noticeable difference and it wasn't a good thing. It definitely felt a little doggy when I'd try to get on it and remember thinking that it just felt "off" the whole time I had that gas in there. Now I know why.
Also kinda sucks that Kwik Trip has seemingly switched to non oxy premium only at almost all of their new stations they put in. Used to love going there as their food/snack selection is pretty awesome compared to other chains (in my opinion), but if I'm driving the WRX it's basically just another unnecessary stop now which is quite the opposite of convenience... Haha.
Yeah and bp who almost always has 93 octane tends to have the worst snack selection. I go to Kwik trip just for the faygo.
The statement on the 91 non oxygenated gas that says “small engines/off road vehicles only” is referring to atv’s and lawnmowers. It doesn’t mean “Subaru” because rally rally rally! You would probably be better off running the 89 octane
Interesting read, i'm going to have to tag all my gas caps at this point. Diesel, 91 oxy, 87 non oxy, 87 oxy
Pricewise, I'm actually paying the same amount for the 91 non-oxy gas at Cenex as reg 91 gas at other stations I've seen. So no difference there. I've filled at a BP about 25 minutes from my home and got their 93, but my buddy who has an m4 said his car was getting lots of knock on his 93 tune using that gas so I've steered clear since as it's a BP converted from a Walmart station so no idea the quality of their tanks. Does Casey's or Speedway 91 oxy have a good reputation? That's really the only other choices I have in my small town for gas stations.
Ultimately, all of that is false. The octane rating is the octane rating. That is federal law. Now how you get to that octane rating can be VERY different. Non-oxy stuff is just old school gas. 91 octane non-oxy is pure gasoline without the additives in it. You NEED to tune for it. The tuning will also react a bit different because of the faster burn rate of the non-oxy. If you tune for it (the whole rpm/load range), it is very beneficial. But you need to tune everything. I was getting close to 30mpg in my FXT with non-oxy and making just as much power as if I was running 92 ethanol. But I had a TON of time in the tune and logging. Base timing maps look completely different than ethanol tunes. But the key is that once you tune to this fuel, if you need to fuel up with any of the ethanol blends, it is no big deal. It is much tougher to go from a ethanol tune to a non-ethanol tune (flame front burns speed). any of the ethanol fuels use a lower grade gasoline and use the ethanol to bump the octane up to the federally required ratings. So a e-15% fuel uses a minimum 15% ethanol blend to get up to their minimum octane rating (be it 85, 89, 91, 92). So your base gasoline is 80-85 octane and they blend in ethanol to bring the octane up to the pump levels. This is why everyone uses e-85 tunes. It is poor mans race gas. The slower burn of ethanol will reach in the cylinder much like race gas. Also much like race gas, if you don't tune the complete rpm/load range you will pay the price at the pump and at under load. Over the years we had many member blow up their motors running 110 race gas as a daily drive fuel. Every one of them was rod bearings. Every one of them tuned 100 under load and completely ignored the cruise down the freeway/basic driving items. So the flame front was burning so slow (and TDC timing was VERY late), the flame front would hit the piston tops just as the piston was hitting BDC. Thus you are constantly getting the full force of the burn AFTER the piston completed the power stroke. Remember, a engine is a engine, doesn't matter if is a 10cc or 1000 liters, it all moves air in and out with some fuel and spark to create the power stroke. The fuel used will determine at what time the spark needs to happen to start the power stroke to turn the crank. I need to run, but ask the questions. I will answer as best as I can later. Russ
Thanks for the info, makes sense! So if I'm on the stock tune for a 19 STI, I could be hurting the engine running this non-oxy fuel as I'm not tuned specifically for it? I would say I'm cruising on the highway 90% of the time and get into boost every once in a while to pass people or just have a little fun. From research I've done in my immediate area, the gas stations only have 91 octane available besides the BP converted from a Walmart station I mentioned earlier. Is there specific gas stations I should try to stick to for good quality 91 with ethanol?
No on the 1st question. Essentially the stock tune has a acceptable window for timing. You might be riding on a edge of the timing window, but the system will allow it. Likewise, running e-15 might be the other side of the window. Subaru (or anyone for that matter) has to make the tunes work for the dumbest of the dumb and the smartest of the smart. This is why stage 1 tunes exist (tune the ecu on a completely stock car). You a altering the safety windows. You add a bit more boost, you change the timing and fueling for the boost you run. You take those safety windows and bring them down to YOUR driving style and fuel. In the mean time, as you add boost, pull fuel, add timing, you are increasing your power. But you are tuning for certain fuels (as described by the tuners). The reason for a 91 and a 93 tune is that the 93 fuel burns differently (Slower), so you can really start to alter the parameters of the fuel/timing/boost (add boost, add timing and remove fuel) and get the extra power out of the system. If you could see inside the cylinders with the engine running, you could create the highest and safest HP/TQ motor ever. You would be able to see the initial spark and you can watch the flame front burn down the cylinder. You would be able to perfectly time everything to create maximum power. I do have a question for everyone. Do you understand how a motor works and the fuel/timing system works? This isn't meant as a put down, I am more than willing to spell out the basics. Once you (or anyone/everyone) understand the basics the rest of the pieces will fall into place. It also allows you to make educate decisions and purchases for your car. Tuning for example. I have seen tunes that make serious power under WOT. Cruising down the freeway they were a driving time bomb. Horrible timing, EGT's through the roof, on the edge of a meltdown. Worst I saw was about 17 degrees of timing (IIRC my forester was 40sih degrees). No power on the road. HAD to get into boost to even cruise up a mild grade. EGT's were super high because the timing was so low that the flame front was basically burning out the exhaust valve. That car wouldn't have lasted 5k miles before the rod bearing would kill themselves. Russ
I would appreciate being schooled on the fundamentals. Even if I think I know there is still more to learn.
Doesn't it say on the pump use for small gas engines and motorcycles or something to that extent? If you only have three options of 87, 89, or 91 non oxy, what would you do? I would almost run 89 octane instead. Thankfully I have a 93 octane BP about 6 miles from my house, and about 1 mile from my work.
Depends on what you are running for a tune. If it is completely stock, I would run the 91, otherwise find another station. If your tune is for 93, you need to find 93. The tuner has narrowed down your safety windows around 93. I am working on a engine 101 post. This week has been pretty busy for me, so I hope to have it posted this weekend. Russ
Tried to go to a semi-local Shell gas station before work this morning and it was closed with no option to pay at the pump. Drove to the city I work in and found a Shell and started filling up 91 as my fuel light came on about 5 min beforehand. Realized 28 dollars into filling up someone had written "non-oxygenated" at the very top of the pump I can't win, gonna have to try another station and pay more attention before filling up lol.
I have a semi-new Casey's near my house, always heard their gas wasn't great. Anyone run Casey's 91 or know if it's generally any good for premium gas?
I avoid Casey's although there is a brand new (not rebranded) station in big lake that consistently has acceptible gas. My biggest worry is older stations that might not be maintaining their tanks very well over brand of station
Video #1 I have not forgotten about this. I have actually stumbled across a better way to explain the basics. I will also include a couple of other videos that show how different fuels burn differently. Russ
