Engine Knocking from Ethanol in Gas Diagnosis

[Hauler]

Don't know if you have an Cenex Station near you but their regular gas is Ethanol free.

https://www.cenex.com/about/cenex-in...d-gas-stations

[Delco Bobby]

The list of Top Tier retailers does not include what I believe are the two major gasoline vendors in The Philadelphia market.

SUNOCO
WAWA a convenience store chain.

I was glad to see COSTCO and Kirkland listed.

If this post is considered stealing the thread the moderators are welcome to adjust.

[GnS]

Originally Posted by Qwkynuf

I'd buy gas at a different location and look for a different mechanic. If the computer is pulling timing to compensate for preignition (which is exactly what it is supposed to do), but is still getting knock, then the simplest/easiest next troubleshooting step is different/better gas.

"Discouraging" using premium is a strange position to take. It could (in theory) reduce gas mileage very slightly, but it can't do harm - other than to your wallet.

On modern engines with knock detection, the computer will advance ignition timing until it detects knocking, and then back it off until the knock stops. It does this hundreds of times per second. The idea is to always run right on the verge of knocking.

The earlier the timing, the earlier the spark plug fires, and the more complete the fuel burn for each engine cycle. More power, better efficiency. If the spark is *too* early, then peak cylinder pressure occurs before the piston finishes the compression stroke. This causes the piston to be fighting against the "flame front" of the burning fuel, which best case reduces power - and worst case burns holes in the tops of your pistons.

The main difference between "regular" and "premium" gas (apart from marketing BS and 20+ cents per gallon) is that premium has additives to make it less volatile so that it is less inclined to self-combust under high compression conditions like you see in performance cars and forced-induction engines. For normally aspirated engines, and under normal conditions, there would be no benefit - in those cases, the computer is not programmed to advance the ignition far enough to take advantage of the increased octane.

This is exactly correct.

[Velosprout]

Read your owners manual. As per the online 2018 E450 manual:

“For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel is most noticeable in hot weather as well as other conditions, for example when towing a trailer.”

Ford built the vehicle; I would follow the owners manual instead of the dealers advice.

[quicky06]

As a non Ford dealer tech ( Honda master tech) let me touch in this.

The tool to measure ethanol is small and cheap it’s nothing more than a graduated cylinder with the correct markings. You add a specific amount of fuel and a specific amount of water and shake it. The water will mix with the ethanol and sink to the bottom. The separation line tells you what your percentage is.

The downside is that it can’t tell the difference between water and ethanol.

12 percent is nothing. Anything under 15 percent shouldn’t cause any issues. Any car made in the last 30 years should have any issues running with e15 and under. People are idiotic to be afraid of it. You cant find gas without it around here.

More Corn fuel will actually increase your octane rating and decrease your gas mileage due to less energy in it.

Most likely what you are running into is you are not using the correct octane fuel. If it calls for 91 and you use 87 or 89 you can get some knock issues. This can actually kill an engine in an Acura TL if people keep driving it hard when knocking. My boss did it to his car.

I’m a Honda master tech, an Ase master tech and have place top 3 in Honda national diag competitions. Additionally I used to build high horsepower turbo ls engines that ram on e85 so I understand the fueling.


Here go buy your own tester.

https://www.amazon.com/REV-X-Super-Tester-Flex-Ethanol/dp/B073HLSVHX

[Sergiop]

If higher octane fuel doesn’t stop the knocking, maybe some Techron injector cleaner will clean any injector that’s not spraying correctly. Causing the cylinder to run lean and knock. The large 20oz bottle will treat 20-22 gal. Run the tank close to empty then put 20 gallons of Top Tier premium with the cleaner. Then go for a continuous 100 mile drive to let the cleaner do it’s job.

A bad or dirty mass airflow meter could be causing a lean mixture.

[dlambers]

I'd be looking for another dealer/opinion if I were you. Ethanol actually has anti knock properties that help replace the tetraethyl lead that used to be used to suppress pre-ignition knocking.

[Reallybigboat]

"The dealer says use Ethanol Free gas but that is extremely hard to find these days."

www.pure-gas.org is a great list of stations around the country that sell ethanol free gasoline.

[Mmgulfcoast]

I use PRI-G in all my vehicles/equipment that are gassers and PRI-D in my diesel pushers. Not only ran better but increased MPG. It’s pricy but worth it... it’s been ten years and countless people I’ve recommended to and never heard a negative word.

[Vladimir1832]

You are absolutely correct. The Mechanic is full of !@#$. Ethanol increases the octane of fuel. If you had higher levels of ethanol, your octane rating would be increased which means more resistance to pre-ignition. On the other hand, fuel efficiency does decrease with higher ethanol levels. NASCAR's race fuel is 15% ethanol for the higher compression engines. Also, a lot of modern engines can handle up to 85% Ethanol (E85) without issue.

[Dakota 1120]

Originally Posted by Hauler

Don't know if you have an Cenex Station near you but their regular gas is Ethanol free.

https://www.cenex.com/about/cenex-in...d-gas-stations

I"ve been forced to stop as several CENEX stations when on the road and EVERY ONE, the only fuel available was an ethanol blend. Only put in eought to get to a station that sold REAL gas and not the ethanol junk fake gas.

[sherman12]

I ran my previous Ford V10 in a class A motor home through the Black Hills of South Dakota, 9% + grades. down south to Nashville and Atlanta and throughout the mountains of northern Maine pulling a car on a dolly at 4500 #'s using 87 octanes and never had knocking or fuel issues with that rig. Now, the V10 in class A's was different that what is provided by Ford for F450 chassis used for class C's, but for the world of me I can't see where that would make a difference.

Also, the OP's rig sitting for weeks on end between uses would have zero effect on his knocking issue. By 2018, Ford had just about perfected that engine to be in my opinion one of the best gas power plants ever produced. To this day, even as I have moved on to a DP, I am still amazed at the performance and durability, and low maintenance I enjoyed from my V10 in my former rig a 2011 Georgetown.

Bad gas, poor BS mechanic is my vote.

[forestwendel]

Google Top-tier Gasoline dealers for a list if brands that meet Tol Tier criteria. TT sets standards for gas quality but the gas usually is no more expensive tha non-TT.

[Larry-NC]

Originally Posted by sherman12

I ran my previous Ford V10 in a class A motor home through the Black Hills of South Dakota, 9% + grades. down south to Nashville and Atlanta and throughout the mountains of northern Maine pulling a car on a dolly at 4500 #'s using 87 octanes and never had knocking or fuel issues with that rig. Now, the V10 in class A's was different that what is provided by Ford for F450 chassis used for class C's, but for the world of me I can't see where that would make a difference.

It wouldn't surprise me if Ford had changed a few parameters in the ECM/PCM (Engine/Powertrain Control Module), otherwise known as "the computer." Perhaps changed based on vehicle weight or rear axle ratio. Maybe the shift points. Maybe the amount of timing advance. I'm not sure you can compare the two.

[JPin AZ]

Originally Posted by Sergiop

A bad or dirty mass airflow meter could be causing a lean mixture.

Very common problem on Ford vehicles. Also check EGR function if it has it. If everything checks good look into someone changing the computer program.

[volare1]

Originally Posted by ArkRVHog

So took my 2018 Forester into the local Ford dealer (E450 chassis/V10 engine) with engine knocking issues. Dealer said they could see computer trying to compensate for knocking and ran a gas analysis from my tank. 12% ethanol content found that they say is causing the issue. (Yes I know 10% is generally the max legally so not sure how that happened!)

The dealer says use Ethanol Free gas but that is extremely hard to find these days. I asked about using Seafoam or Sta-bil with ethanol gas and he really discouraged me. I asked about using Premium gas as my norm (many times it does not have ethanol) and he discouraged that too since my engine is made to run using 87 octane regular.

So I'm kind of stuck in how to approach this moving forward...particularly to minimize/eliminate my knocking issues. I'm sure some of the gas burners have figured out the best "cocktail" for these engines and performance and look forward to your input.

I went to the Ford dealer with the same issue. They checked the computer and told me to use premium gas. The engine knock went away. I am going to try mixing mid grade with premium in the spring when it is out of storage. Mine is also a 2018 E450 V10.

Here is what the Ford Technical Department said:
We found no service publications related to the concern you have described and no similar reports on like units. Per page 77 of the second printing of the online owner's manual, it recommends that customers use premium gasoline and should not be concerned if the engine knocks lightly someFord Knock report.pdftimes.

[mrfikser]

If the vehicle was designed to run well on regular octane fuel and it won't, take it to be fixed...the problem is not the fuel it is the vehicle...saying it is the fuel is like blaming a fever on the thermometer, thermometers don't cause fevers, they just report a symptom...So, that said, find another repair shop...and for all you dinos that still blame alcohol for your engine issues, all you need to do is fill your gas cans with the alcohol poisoned gas add a cup or 2 of water, give it a good shake, let it sit a half hour or so and pour you pure 100% virgin gasoline (plus other additives) off of the top into your vehicle, leaving the small amount of water/alcohol mix in the bottom of the can to water your wifes tomatoes with...you will lose some octane by doing so, but you can replace that with a can of octane booster if your unadulterated fuel won't get the job done on its own.

[grumpyoldman]

For those of you that state that ethanol increases the octane of the gasoline, that is true. Knowing that, the refineries produce a lower octane fuel, which is cheaper to do, so when the ethanol is added the octane comes up to the advertised number of 87,89,or 91. You are not getting a higher octane than what is advertised. Also high octane gasoline is not regular gasoline with more additives. It has to go through additional processing at the refinery to increase the octane. That is the reason that high octane gasoline costs more than low octane gasoline.

[dacheedah]

Running boats we did tests and all gas is not created the same. In fact most discount gas creates a problem with small engines and we avoid it and pay a few more cents for the bigger box gas. If it's knocking step up to the next ethanol number 87 to 89 just for that fill and go back at a big gas station. Our boat mechanic took samples from several gas stations and started asking customers that had problems with engines where they got their gas. He had jars the filled mid fill up and tested each and had them to show customers. Cheap gas is not less expensive when it causes you problems. Your mechanic is correct that you should be sticking with the 87, higher grades are actually made for high compression engines that are prone to pre ignition and most cars and trucks that use higher than label octane often actually have poorer performance. Every gas has chemicals added so adding another is really not recommended.

[TheWolfPaq82]

“For every expert, there is an equal and opposite expert.” (Arthur C. Clarke)