Anyone know if it's safe to run seafoam through a 2.5i?

[DrD123]

Is the car 87 octane only? I read in my owners manual that you should use 87 octane fuel or higher. I'm a bit confused on what that means, but I've been using 93 octane recently and notice no difference, only a little better fuel economy than I got with regular.

You can safely run what the car is expecting/tuned for (87) or higher - higher yields increased resistance to detonation. At least one person has logged and found knock on 87 in their 2.5i (see post above) so might be a good idea to run the mid-grade. 91 or 93 is a-ok, too - you just might be paying a little extra for performance you can't take advantage of.

[dgoodhue]

Modern engines are calibrated to be right on the edge of knock - that's where the most efficient point is. Pulling around two degrees of timing when the engine is making good power (on its recommended fuel) is pretty standard from a production calibration perspective.

 

That being said, you can get a very small bit of power back from that two degrees, say by putting 93 octane in a car intended to run 87, as its almost guaranteed to have no knock.

 

If I have a chance tonight, I will post a picture of the Knock Correction Table for my 2012's 2.5i. It has zero correction in most cruise situations, some correction 4-6 degrees in the high load low RPM (hill and aggressive acceleration) and 8-12 degrees of correction in the area where the WOT loads would be.

 

The DAM multiplies the timing of this table and adds it to timing table that ECM is using (cruise non AVCS, non cruising AVCS, AVCS cruise & non cruising timing tables). For 0.5 DAM, the engine would see 4-6 degree less timing at WOT. While it may see 2-3 degree less in the high loads/low rpm & acceleration, which the average owner probably isn't going to notice.

 

If one is more interested in reading about tuning, this owner did far more than I ever did.

 

https://legacygt.com/forums/showthread.php/diy-retuning-2-5i-257239.html?highlight=

[5thGenCVT]

Ya now that I think about it, I somewhat want to try running a tank full of 91/93 Octane once it's time to refill. I'm curious to say the least, but at the same time I don't know if I want to risk it... from what i've read up most people said they didn't see an improvment with anything over 87 octane and some people even said they had pinging or knocking too.

 

You may not notice a difference, at least I didn't, just slightly better gas mileage probably so take that into account on whether or not it's worth it.

[Alexmed2002]

You may not notice a difference, at least I didn't, just slightly better gas mileage probably so take that into account on whether or not it's worth it.

 

I mean I haven't had any issues while running only 87 octane... that's why I don't really feel comfortable going with 91/93... I did buy some Chevron Techrone though.

[amusa]

<- 2013 2.5L I only put 87 in. I only fill up at Sunoco or Exxon and my wife sometime fill up at Shell.

[YeuEmMaiMai]

87 here in both cars, no issues either one... 2003 Legacy is at 140K, I am at 64K

[SchwarzeEwigkt]

I mean I haven't had any issues while running only 87 octane... that's why I don't really feel comfortable going with 91/93... I did buy some Chevron Techrone though.

 

 

 

Running fuel with a higher AKI definitely won’t hurt your engine. There’s no reason to be uncomfortable about it besides that you’d spend more money.

 

If your engine was in perfect condition, a more stable fuel — which is actually what AKI represents; it’s relative resistance to detonation — wouldn’t make a lick of difference. Well, you might get slightly better mileage due to the your wallet saving you some weight! If you’ve got things going on that would make the engine more prone to knocking, say carbon buildup or something, a more stable fuel might result in fewer knock events and thus ignition timing getting retarded less often. You might get more energy for a given amount of fuel. Really, you’d probably be getting closer to the energy you probably should get from the lower stability fuel you should be able to use.

 

It might be a fun experiment to run a few tanks of 93 just to see what happens. Frankly, though, if you’re having to run premium fuel to keep knock under control and you’re not running a ton of boost or some crazy high compression setup, you’ve got problems you really should consider fixing before they get worse.

 

 

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[Alexmed2002]

<- 2013 2.5L I only put 87 in. I only fill up at Sunoco or Exxon and my wife sometime fill up at Shell.

 

Yah Sunoco is like 3 or 4 miles away from me, shell is like 10 to 15 miles away

[dgoodhue]

Here is the knock correction table for my 2012 2.5i. I don't know how well you can see it, but left is rpm, the top is a derivative of air flow. My 2.5i at WOT would be at 1.10-1.30 grams/rev. Idle was 0.25g/rev. The part that bumps out is usually the high load/aggressive throttle area.

[Alexmed2002]

Running fuel with a higher AKI definitely won’t hurt your engine. There’s no reason to be uncomfortable about it besides that you’d spend more money.

 

If your engine was in perfect condition, a more stable fuel — which is actually what AKI represents; it’s relative resistance to detonation — wouldn’t make a lick of difference. Well, you might get slightly better mileage due to the your wallet saving you some weight! If you’ve got things going on that would make the engine more prone to knocking, say carbon buildup or something, a more stable fuel might result in fewer knock events and thus ignition timing getting retarded less often. You might get more energy for a given amount of fuel. Really, you’d probably be getting closer to the energy you probably should get from the lower stability fuel you should be able to use.

 

It might be a fun experiment to run a few tanks of 93 just to see what happens. Frankly, though, if you’re having to run premium fuel to keep knock under control and you’re not running a ton of boost or some crazy high compression setup, you’ve got problems you really should consider fixing before they get worse.

 

 

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My car runs great, and that's good and all, but now that I hit 84k miles I am starting to think of how to keep my car alive for as long as possible. I'm thinking about running Sunoco 93 Octane gas to be honest because of the additives, but do they put that amount of additives in 87? That's the question I wonder about...

[dgoodhue]

My car runs great, and that's good and all, but now that I hit 84k miles I am starting to think of how to keep my car alive for as long as possible. I'm thinking about running Sunoco 93 Octane gas to be honest because of the additives, but do they put that amount of additives in 87? That's the question I wonder about...

 

Regular and Premium grades of fuel now have the same cleaning detergents in them. It wasn’t always that way. I believe their was law put in place to not force consumer to buy premium gasoline to get the cleaning detergents.

[SchwarzeEwigkt]

Regular and Premium grades of fuel now have the same cleaning detergents in them. It wasn’t always that way. I believe their was law put in place to not force consumer to buy premium gasoline to get the cleaning detergents.

 

 

 

I have read that they have the same detergent packages in different grades of the same formulation of gas now. Never heard there was legislation to that effect, but it definitely would explain it!

 

What I’ve always wondered is precisely how they increase the AKI on premium fuel. They’re allowed to put a maximum of 10-15% ethanol into it, depending on the municipality. Ethanol is really cheap and is very stable; it’s why the ethanol-free gas you find tends to have a lower AKI and why dudes who run giant turbos frequently run E85. I can’t help but wonder if the premium stuff is the same base stock with more ethanol in it than they put in the regular stuff.

 

I don’t know enough about the economic or the science of it to know if that’s even feasible, but my tin foil hat is tingling a little.

 

 

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[Alexmed2002]

I have read that they have the same detergent packages in different grades of the same formulation of gas now. Never heard there was legislation to that effect, but it definitely would explain it!

 

What I’ve always wondered is precisely how they increase the AKI on premium fuel. They’re allowed to put a maximum of 10-15% ethanol into it, depending on the municipality. Ethanol is really cheap and is very stable; it’s why the ethanol-free gas you find tends to have a lower AKI and why dudes who run giant turbos frequently run E85. I can’t help but wonder if the premium stuff is the same base stock with more ethanol in it than they put in the regular stuff.

 

I don’t know enough about the economic or the science of it to know if that’s even feasible, but my tin foil hat is tingling a little.

 

 

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Ya I kind of wonder if they'll ever make it so that companies have to tell consumers what's in their gas... kind of like a nutrition label for food but for gas.