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My 2014 limited did great on E85, with the exception of lower MPG. It was especially great when the price difference between E85 and 87 octane was almost a $1. Then they jacked the E85 price up and made the difference negligible. I have not run E85 during the winter because I feared my MPG would be worse yet. I am considering going back in a few weeks when it warms up consistently... cost difference last I checked was about .65 cents.
 

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Discussion Starter #22
Another update. Been 3 weeks now and things have definitely changed. At first long term fuel trim was the only one that Immediately changed but after about a week and a half short term followed. Everything Is still running great. On cold mornings after It's sat for about 10 hours or more It will start fine but stall Immediately (unless you give It gas) but start right back up. Another thing If It's running and you shut It off and Immediately try and restart It. It will do a long extended crank and crank over for about 5-10 seconds. While It's cranking over It try's to catch and fire. Sometimes It will fire after a few seconds and sometimes If It cranks too long the ECU will kill the starter to prevent damage to It. Idk If It's getting too much fuel or not getting enough but It's never failed to start or have drivability problems. Fuel range and Instant economy have also adjusted. Before this trip fuel range on a full tank was only around 170 miles. That's city driving and me gunning It every chance I get. Also before when It would go Into 4CYL MODE It would switch back to 8CYL MODE when the Instant MPG dropped to 18-17. But now with e85 In 4CYL MODE It will drop as low as 12-11 MPG before switching back to 8CYL MODE. I actually drove It to zzperformance to get the dog bone poly mounts set as I only live an hour away from them. State Troopers were all over the highway so I couldn't speed too much. So with the cruise set between 70-80 MPH according to the car I averaged 15-16 MPG. I drove It gentle but did get on It at times when passing people. I started out with a little over 3 quarters of a tank (75% full) and ended with a little under a quarter of a tank (25% full). Round trip was about 80 miles both ways so 160 miles In total. But It still consumed quite a bit of fuel for as gentle as I was driving. Anyway I just put another $30 bucks In the tank (e85) and that almost filled It up and now fuel range Is at 240. Obviously fuel range goes up the more efficient you drive.

Bottom line Is when I first started this little experiment I just wanted to see how the LS4 reacted with e85 and If It would run correctly. So It's good to know that the ECU can compensate for e85 and make It run correctly and the pump and Injectors have no problem keeping up with e85. Im not saying I won't ever go back to normal gas but It's just good to know that I can run either fuel without problems other than a check engine light for lean conditions. I also stated In a previous post that I thought e85 killed my catalytic converter. Apparently It didn't kill It as the computer was just adjusting and the p0420 code only appeared one time and has not been back after 2 weeks. So In the end Im happy with the way the engine runs on e85. It has great performance but you do pay for It In MPG's. And to top It off I added these... Flex Fuel badge.png

E85 cap.png
 

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I filled mine on Friday morning because I saw the one station was almost a $1 cheaper on E85... $1.59 a gallon... $21 to fill it. I drive fairly conservatively but work called and bumped my start time by 45 mins so I had to hustle in... almost 80 the whole way in... so there goes this weeks real mpg test. Looks like the weather is going to stay 60° to 70° pretty consistently here.
 

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Discussion Starter #24
Giving this another update. Been about a week now since I switched back to 87. I ran the tank very low and filled with 87. Fuel trims went Into negative obviously. But power went up. I Immediately noticed an Increase on 87 vs the E85 as at WOT the PCM Ignores the 02 sensor's and defaults to the factory programming weather It's running lean or rich. The reason I switched back was It started hiccuping anytime I would put It to the floor as It was going Into open loop and taking away that extra fuel and It was starting to have trouble starting up when sitting overnight. So now everything Is back to normal and the power Is back. 0-60 on E85 on a cool morning with a perfect launch was a tad over 7 seconds. 0-60 on 87 with a bad launch was dead at 6 seconds. So even though E85 Is cheaper It's not worth It without a tune. I filled up about 4 days ago and just hit the half mark.
 

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Giving this another update. Been about a week now since I switched back to 87. I ran the tank very low and filled with 87. Fuel trims went Into negative obviously. But power went up. I Immediately noticed an Increase on 87 vs the E85 as at WOT the PCM Ignores the 02 sensor's and defaults to the factory programming weather It's running lean or rich. The reason I switched back was It started hiccuping anytime I would put It to the floor as It was going Into open loop and taking away that extra fuel and It was starting to have trouble starting up when sitting overnight. So now everything Is back to normal and the power Is back. 0-60 on E85 on a cool morning with a perfect launch was a tad over 7 seconds. 0-60 on 87 with a bad launch was dead at 6 seconds. So even though E85 Is cheaper It's not worth It without a tune. I filled up about 4 days ago and just hit the half mark.
Why do you think things started acting up? Will be curious to see how things go on from there. The alcohol in flex fuel is not good for cars not designed to run on it, think some here said as much. With seeing the after effects of small engines run on gas "with less than 10% ethanol", I have my suspicions.
 

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Discussion Starter #26
Why do you think things started acting up? Will be curious to see how things go on from there. The alcohol in flex fuel is not good for cars not designed to run on it, think some here said as much. With seeing the after effects of small engines run on gas "with less than 10% ethanol", I have my suspicions.
I'm not sure. I'm guessing fuel trims are playing a big role. I lived with It hiccuping for about 2 weeks and then on my way home the other morning me and a 3.6 Impala punched It around 80 and It gapped me so much It wasn't funny. That's when I realized something was wrong. Again at WOT It Ignores the 02 sensors and goes back to the factory tuning and doesn't give It that extra fuel that Is required when running E85. If It was tuned that would be different but It's not. Leaving work after It had been off for 8+ hours would make It start and Immediately stall, It stalled 4 times before It would stay running and that was with me holding the pedal about 75% down any further and It would just go Into clear flood mode. Even when the engine was hot It was starting up poorly. It even threw an 02 sensor code P1133. But everything Is good now, no more engine light, no more stalling and no more extended cranks.
 

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The engine Itself Is e85 safe as every Internal engine component Is Identical to a flex fuel model with the 5.3.
What year is this again? The reason I ask is the wife's cousins husband is the 2nd in charge at a large salvage lot here in Eastern South Dakota, Nordstroms Auto and he even said back when E-85 was first popular that the engines are assembled differently because the E-85 has more corrosiveness. I wouldn't take the chance myself.

Can I ask who told you the engine parts are all the same?

Rule always has been if it's E-85 capable it'll have it marked in the fuel door on the fuel cap and in the owners manual. I'm sure the VIN# may have a designation or the RPO code could tell you that as well.

Sent from my SM-N960U using Tapatalk
 

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Rule always has been if it's E-85 capable it'll have it marked in the fuel door on the fuel cap and in the owners manual. I'm sure the VIN# may have a designation or the RPO code could tell you that as well.

Sent from my SM-N960U using Tapatalk
Good point, hope the op removes the flex fuel cap and emblem. Could make for confusion for others.
 
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