e85 "rotation" necessary ...
 

So I've been running e85 pretty much exclusively on OFT standard e85 2+ tune for a little over 5 months (big thanks to the Alternative Fueling Station locator app) with zero issues. Early on I would check the trims after new tanks but stopped doing it since they were always fine and always pretty much the same.

So, my question is is there any reason to rotate to a few tanks of 93 before switching back? And if you say yes, please provide me with a sound, well-reasoned logical reason why - what does it help? What does it do?

BTW - my same response would go to the guy down below who said "don't fuck around and go with flex fuel system" which I disagree with entirely. Don't get me wrong, I have no issues with guys running flex fuel and it is a handy set-up particularly if you live somewhere with little e85 availability (not generally the case here in the midwest). I also happen to think you are as likely, if not more likely, to have an issue running flex fuel and constantly changing back and forth than someone like me who doesn't and only and consistently runs e85 (most of it from the same station).

doesn't hurt to run some e10 to 'clean' out the lines periodically since the car isn't rated for full e85.

you don't want e85 to be in your tank for an extended period of time. it's generally accepted e85 doesn't store well compared to e10.

Not sure why people believe flex-fuel would be more of an issue than straight E85. In any case, to give a general answer to your question, I don't see why you would need to run 93 through your car. E85 runs cleaner through your fuel system than 93 and helps eliminate carbon buildup, etc. I don't believe there is any actual reason out there for why 93 would be used to "clean up" after long E85 use, certainly none that I have ever read or run into.

The only thing you really need to care about when running E85 is proper care of the vehicle. I assume you are aware that E85 wants to absorb moisture - which can lead to corrosion and such for fuel system components. So take better care of these components (check them / change them more often than typical service intervals may require). Clean your injectors every 30-40K miles maybe. Replace the fuel pump at a shorter interval than recommended - and maybe with an aftermarket that is meant to handle E85. Inspect fuel lines and regulator at times.

The easiest care I can think of to have less worry about all these components is just doing the right things to avoid any water buildup in your fuel system. Don't leave the car sitting around for long periods of time being the big one. Keep your fuel topped off as much as possible is another big one - don't drive the car to empty all the time, and in general avoid it.

The benefit of having flex-fuel in my opinion is just simplifying the worry about some of those things. Because gasoline doesn't absorb moisture, so you reduce that risk (that's pretty much the #1 reason in my opinion that flex-fuel has the upper hand). It also adds benefits in dealing with cold starts. Aside from all that, there isn't much more that I can think of off the top of my head. Flex or straight has proved to work completely fine. Ethanol, in general, just requires a little more care and maintenance to help avoid any future issues.

The WRX high pressure fuel pump will seize up if running too much e85 under certain scenarios. Running e10 usually resolves this issue.

The components aren’t rated for straight e85 and any suggestions is really just based on anecdotal evidence, so use your best judgement.

Anyone use this

https://www.google.com/aclk?sa=l&ai=...w&dct=1&adurl=

Thanks for the help/information. Not sure I understand the person who suggested the e10 occasional clean out vis-a-vis the fuel pump. Either the e85 is going to cause the fuel pump to go or it isn't, right? How would running an occasional tank of e10 "clean it out" and prevent that? It doesn't make any sense to me.

Don't misunderstand what I am saying about flex fuel - I think it is fine assuming everything is working properly. But I think using it and frequently changing what you are running (thus constantly changing your tuning) is more likely to run into an issue with having the wrong tuning than running the same fuel all the time. Of course, it does have the benefit (which probably outweighs my issue) of being able to change tuning depending on the ethanol percentage of the e85 you are running (given it technically can run 51% - 83%).

Understand what you are saying about water and leaving it sit for long periods with e85. Good news is it gets driven frequently and the longest it has ever sat is one week. The drives are generally exactly the kind you would like - commute for 25 minutes on mostly highway miles.

As for the fuel pump, other than getting stuck somewhere in an inconvenient location (which I am not too worried about), don't see why I would ever change it before it fails (if it ever does). It's not a "maintenance part" and other than above, its failure is not otherwise dangerous to other parts of the car.

Also not sure about the advice of cleaning injectors. Seems to me like e85 users should be on a longer, not shorter, interval for cleaning injectors than e10 users would be, right? Am I missing something? How do yo clean injectors?

like i said, this is all anecdotal evidence. your car isn't rated for more than e10, so if you have issues with e85, you're kind of ow your own.

some wrx owners who are tuned on e85 will have issues with their high pressure fuel pump. tuners suggest staying below e60. the theory is that e85 has less lubrication than e10, therefore, it seizes up. emptying the e85 with e10 usually fixes the issue. is it just the fuel or are there external variables causing the fuel pump failure? who knows.

keep in mind there are diminishing returns once you're above a certain ethanol level. for example, the wrx gains the most at e30. after that, there are diminishing returns. so there's no point in running straight e85 other than not having to mix, which the flex fuel solves that issue for you.

He may be miswording it a little. I believe he is simply trying to say that our platform is not rated for running E85. I do not believe E10 will CLEAN anything out more than E85, as E85 should do a better job at that. But E10 will attract less moisture, therefore posing less risk to the fuel system components. Not very knowledgeable on the the WRX platform, but my guess is E85 makes it fail quicker due to the amount of work the fuel pump has to do. That is often the fail point as E85 will require the fuel pump to work much harder due to the lower energy content, requiring far more fuel to be pumped. On top of that, a vehicle is often tuned on E85 to produce even more power, therefore requiring EVEN MORE fuel. Unless there is evidence of corrosion or some other type of problem with the WRX, BRZ, or any platform for that matter, I don't see how the fuel itself is doing any damage to the pump.

Agreed, this is why if you go this route, it is quite important to go with a good tuner and probably spend the bigger bucks. Another thing @ayau mentions is that various platforms only benefit so much from ethanol. In the case of the twins, most of the gains are around E50. So this is another large benefit to having flex. Not only will you get a decent bit better gas mileage running E50 vs E85, but with a good tune, the AFR can be pretty precise for any ethanol, including E50 for close to the max power potential. A pure E85 tune is really setup for something like E70-E80 IIRC, and probably varies based on the tuner. So if you are running true E85, your AFR will likely be slightly off of ideal and therefore not perfectly tuned for max potential.

This type of stuff is most important, in my opinion, to keeping a vehicles components in good shape and not reducing their lifespan as much when running E85.

Inspecting the fuel system every 30K miles is under the Subaru maintenance schedule. At 72K, the fuel filter should be replaced. But again, when running E85, you are putting far more stress on the fuel pump than what it was spec'd for. So yes, you may not need to ever replace the pump, but using a fuel the car was not designed for, this may be something to consider. The worst that happens is your fuel pump fails in the middle of your drive and your car stalls out, in which case you would need to safely pull over - this could be the potential risk depending on where and how fast you're driving.

Correct, E85 would actually clean the injectors and other fuel system components better than E10. But the risk of moisture in the system remains for high ethanol. It only takes a tiny bit of moisture to buildup during a period the car sits a little while and maybe on a humid week. That tiny bit will be enough to cause corrosion/rust buildup - which is what does damage to components like the injectors.

Theoretically, you're right about all the maintenance thoughts, you shouldn't have to do as much maintenance with some of the items, aside from the fuel pump possibly due to it working harder. E85 does clean the system better and prevent gunk from building up. But as @ayau stated, there is not enough evidence out there for us to make clear conclusions. How long can your car sit before moisture gets into the fuel system? What kind of temperatures and humidity could cause this to happen much quicker, and how fast? There can be so many different factors. Which is why if you at least follow the general care guidelines that we've discussed, you are already doing the best you can to prevent any problems.

As a side note, I only know of one shop (I'm sure there are plenty others out there) that does injector cleaning.
https://www.counterspacegarage.com/f...-86-subaru-brz

Plenty of people get this when going forced induction, why do you ask?

One of the bigger issues with e85 is that it is more corrosive to rubber parts. There are lubricating additives that you can add to your tank if you are concerned with that. There is enough long term data on running e85 on here I am not too worried about it. I wouldn't store the car for longer periods of time with e85 as it is also more hygroscopic then fuels with lower ethanol content.

Just getting my gameplan in order for when I decide to go FI

So far I'm at 4 yrs and 40k miles on e85.

Ive run E85 for almost 8 years, no additives, stock fuel system , 80,000 km no issues, not run any petrol in thst time.

To keep your injectors clean. E85 doesn't have cleaning additives. The "cleanness" or "corrosiveness" has nothing to do with keeping the injectors clean.

To everyone else who says they have no issues: Have you ever flowbenched your injectors after just being on ethanol for a long time? Independent data my surprise you and change your mind very, very quickly.