hi guys just curious if any of you ever ran E85 in your Monte (or other GM) and if it gave noticeable performance gains? Mine is a 3500FFV and I have always wondered what it would run like on E85. I assume HP would be increased? I know the tank needs to be empty before filling with E85 for the PCM to switch the profile.

 

Yes, I converted my 96 to E85. No noticeable performance gains from the swap itself, but was able to drop pulley sizes on the supercharger. I can pulley down at least to what the belts slippage limit with no signs of knock at all. Id bet i could squeeze 50+ whp gains out of it if I could get the belt to hold.

I've done this before on my stock 3500 Impala.

What it was like:
-zero noticeable power gain (E85 is higher octane, but you need something that requires higher octane to take advantage of it - more compression or boost. A stock engine at most will restore any timing lost to KR, but likely even a few degrees will be completely unnoticeable to the driver).
-Worse gas mileage - it gets about 1/4 - 1/3 less mpg depending on the blend. Closer to true E85 gets worse.
-Saved money (at the time). Where I lived, E85 was right about half the price of 87. So even with worse fuel economy, it still was beneficial. Will really depend on your local price ratio. Here in the PHX metro today, its almost the same price as premium gas (meaning it would be significantly more expensive to run since the fuel economy is so much worse - especially for someone who normally runs 87).
-Exhaust fumes smell funny

That's not correct. The factory flex fuel vehicles have a sensor to read actual E% and adjust fueling accordingly (they have to as winter mix is often nowhere near 85% in most part of the country). You can dump in as little or much as you want as long as you don't exceed E85 (ie don't fill up with only E98 / E100).


My .02: for a stock car, I wouldnt bother unless the economics works out (its cheaper enough than 87 to offset the mpg loss). For a boosted car - go for it and crank the boost.

 

Lots of good info thanks for your reply!
I didn't think about it benefiting a supercharger/turbo like you said but makes sense.

I thought I read in the manual about filling the tank with one fuel or the other so I looked it up again it says: "It is best not to alternate repeatedly
between gasoline and E85. If you do switch fuels, it is recommended that you add as much fuel as possible — do not add less than three gallons (11 L) when refueling. You should drive the vehicle immediately after refueling for at least seven miles (11 km) to allow the vehicle to adapt to the change in ethanol concentration." But it also says if you have trouble with E85 in cold weather you should add some gas so... a little confusing.

I figured the cost would be higher for now but I remember several years back it was getting cheaper to buy E85 since the gas price was high (like now). I guess if you live in Iowa or Nebraska probably E85 all over the place for cheap!

 

TBH, I never noticed that in the manual and we've had a couple GM flex fuel vehicles that we dumped in whatever / whenever and never had an issue. That 08 Impala jumped back and forth between fuels for probably 6 or 7 years of its life with no issues (my parents owned it first - Dad hated E, Mom loved how cheap it was - then we bought it and I used E for the cost savings while my wife would just fill up wherever so it usually got gas from her). Between the two fuel maps + fuel trim adjustability on top, you shouldn't have any issues (especially since the E map needs to handle a huge range E50-E85 on its own).

The starting thing is only a concern if it gets really cold in your area. In colder climates, they'll automatically drop it to near the min in winter anyways (E51-E54). It never got crazy cold in our area, -10 for a typical low maybe with an odd one night spike down to -15. But we never had a single issue starting it on winter E. I do know its harder to start in the cold, but Ive never seen a factory vehicle struggle in the temps we saw. Seemed like the only people that had issues were with aftermarket conversions.


In your case though, I'd just math it out with the price at the pump to see if it makes sense with the fuel cost vs reduced mpg. If you're not saving money, I wouldnt even bother trying. Like I'd mentioned, here in the PHX area lately its been about the same price as premium so its an awful value proposition for someone who normally runs 87 gas.

 

Thanks for your reply and info I wouldn't be as hesitant to try it out now. Like you said if the math works I will try it (esp the way gas prices are going) but def won't pay more for it.
Interesting how specific the manual is on it and other things yet doesn't seem to matter. Its kind of like oil weights in the manuals (not just GM) they talk like you will destroy the engine if you put heavier oil in it. That's for another thread though...

 

One time we got it mixed up on the pumps and it went into a 2006 Pontiac torrent SUV with a 3400 motor in it.
Mixed into the normal fuel too and we were heading to Colorado, it was hot out and with the altitude the car got sluggish and a bit warmer that normal. So we never did that again.
That what happens when the passenger fuel the thing up and I went in the station to use the restroom.

 

Well at least she didn't put diesel in it!! A friend of the family put a full tank of diesel in her car (HS student) a few months back and it didn't run so well on that!!

 

E85 is pure crap and loaded with ethanol. Good for race cars, bad for street cars. Even when I could buy it 50 cents cheaper a gallon for my flex fuel Impala the mileage was so poor that unleaded was still a better choice. Reason being is that the closer you get to alcohol/ethanol the more fuel it takes. Your Air/Fuel ratio is probably 10-1 with that crap. Normal car is around 14-1. When I ran pure alky in my race car it was 6-1. As noted above, it takes more squeeze to run it, and if you are running a supercharged 3.8 you are already down to 8-1 compression.

 

Of course its loaded with ethanol, thats literally what it is - ethanol mixed with gas. Its not like its some kind of secret.

I completely disagree for two main cases:

-E85 isn't as consistently priced around the country as gas is. Many areas (especially in corn producing areas) have additional subsidies for E85 that bring the cost down. As such, there are parts of the country where the price of E85 is more than 30% cheaper than gas (which then offsets the added fuel usage and starts to amount to a cost savings). In these areas, even for a stock NA daily driver, it can be a good financial option for a flex fuel car.

-There are a lot of people with boosted cars that actually care about making power, even for street cars. In this case, E85 is extremely cheap race gas thats widely available in many areas (often with better power results than 100 unleaded). There plenty of people who arent willing to pay $8-10/ gal for race gas for their hopped up street car, but are willing to pay $4/gal for E85 (even if the net is a small financial loss per gallon over the cost of premium). I'm exactly in that boat with my monte and have been running e85 exclusively in it for years for this purpose.


I will agree that its not for everyone. In areas where the financial prospect doesn't make sense due to E85 vs gas cost and for people that aren't modding boosted cars - then its certainly not a smart application. I just disagree completely with the blanket statement that "its bad for street cars" across the board.

The SC 3800 is 8.5:1, but TBH compression isn't the factor in needing more octane on it - its the boost. Even on premium fuel, the SC 3800 usually can't even drop a single pulley size without running into knock issues. So you either have to add mods to compensate or pull timing (which only gets you so far as power starts rolling off pretty quickly when you get too low).

Or, you can just swap to E85 and run pretty much any pulley size you want with no other performance mods. Its honestly a very common mod path for boosted 3800s today. When faced with the prospect of thousands of dollars in mods (heads, cam, headers, intercooler, ported blower, tb, etc) or a simple E85 conversion thatll allow a major pulley size drop while still giving the majority of the power gain - a lot of people would rather go E85 (especially those not looking for an all out build - they just want more power in the easiest way possible), even if it means another $10 every fill up.

The other thing is its very popular on 3800s and they aren't even flex fuel compatible (ie you have to load one fuel map - the pcm cant make changes on the fly from an ethanol sensor). Its honestly a bit of a pain on 3800s - especially if you live in an area not saturated with E85 pumps - and yet its still a popular mod. When you start getting into platforms that can run true flex fuel maps (LS stuff as one example), its FAR more common on street cars.

 

First of all, racing on the street is for morons. Second, produce some time slips that prove E85 is better than high test fuel. I provided the Air/Fuel ratios for all of the options. (I was even off just a bit - it's 9.3-1). It will not combust better, and you have to use a LOT more. So what do you gain? I ran 15-1 compression in my race car on alky. Only way to make it work. Most of this crap is only popular because some company told you it was, and your buddy has one. Just like jacked up trucks that serve no purpose. Or the suckers that buy K&N filters that terminate under the hood with nothing but hot air to breathe. A stock filter actually takes in more outside air. I ran a 16 channel data recorder on my cars, I have a clue about HP, EGTs and performance. And while alky takes a 6-1 ratio, we bought it by the drum for $90. But it's your car, do as you wish.