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Old 06-27-2022, 06:23 PM   #1
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Questions about Octane on an F-150

I've read several debates now about octane levels in F-150s. And I guess I'm risking opening this debate here now, lol! This is what my Ford manual says:

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Your vehicle operates on regular unleaded gasoline with a minimum pump (R+M)/2 octane rating of 87.

Some fuel stations, particularly those in high altitude areas, offer fuels posted as regular unleaded gasoline with an octane rating below 87. The use of these fuels could result in engine damage that will not be covered by the vehicle Warranty.

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.
I'm towing a Flying Cloud 23 Corner Bunk Bed (6000-lb GVWR, have not weighed it yet, on my list to do soon) with a 2021 F-150 Crew Cb Short Bed (5.5') 1808 Payload capacity, 7050 GVWR.

Should I consider using 91 octane fuel? (We currently used 87).
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Old 06-27-2022, 06:44 PM   #2
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You don't mention which engine is in your F-150. If it has one of the turbocharged Eco-boost engines my suggestion would be to opt for premium. Forced induction engines have higher effective compression ratios than normally aspirated ones and are more prone to pre-detonation with lower octane fuel. Their knock sensors will minimize this issue but at the expense of power. Honestly, even if you have the NA 5.0L V8 I would choose premium when towing.

Under normal conditions around town 87 octane is fine. But under heavy load like towing a TT, I think 91 is a better choice if you want optimum performance. Just my $.02 but based on your owner's manual it appears Ford would agree.
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Old 06-27-2022, 07:01 PM   #3
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I have burned premium while towing with my 2020 F150 and I have a 3.5 Ecoboost. Complete waste of money. I don’t see any performance change at all from 87 regular. I have also tried the mid-grade. No difference that I can perceive. And for the extra cost certainly not worth it.

Maybe if you were towing in the mountains you would notice a change.
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Old 06-27-2022, 07:05 PM   #4
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Quote:
Originally Posted by mikeinca View Post
You don't mention which engine is in your F-150. If it has one of the turbocharged Eco-boost engines my suggestion would be to opt for premium. Forced induction engines have higher effective compression ratios than normally aspirated ones and are more prone to pre-detonation with lower octane fuel. Their knock sensors will minimize this issue but at the expense of power. Honestly, even if you have the NA 5.0L V8 I would choose premium when towing.

Under normal conditions around town 87 octane is fine. But under heavy load like towing a TT, I think 91 is a better choice if you want optimum performance. Just my $.02 but based on your owner's manual it appears Ford would agree.
Whoops, yeah, neglected to include the engine. Yeah, we have the 3.5L EcoBoost (twin turbocharged). Yeah, that makes sense.
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Old 06-27-2022, 07:11 PM   #5
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Originally Posted by Daquenzer View Post
I have burned premium while towing with my 2020 F150 and I have a 3.5 Ecoboost. Complete waste of money. I donít see any performance change at all from 87 regular. I have also tried the mid-grade. No difference that I can perceive. And for the extra cost certainly not worth it.
Yeah, I haven't noticed any knocks or anything too weird when towing so far. But we towed less than 200 miles so far, and not honestly sure I'd know what I was looking for. I worry a little about the things that I don't "see."
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Old 06-27-2022, 07:13 PM   #6
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When I first got my 25' flying cloud, I had a 2016 F-150 with the 5.0L v-8 (aka the "coyote") and I always burned regular (87 octane) in that. Now I have a 250 with the 7.3L v8 and burn 87 in that as well. Never felt like I needed higher octane, and I always said I had plenty of power with the 5.0, but the trans would do a lot of downshifting to stay in the right power band (high RPM). With the 7.3L/10sp I have an order of magnitude less downshifting, but still do get it on occasion. Primary reason to upgrade the truck was I wanted a heavier tow vehicle chassis and for me it was definitely worth it. I don't doubt that if you had enough instrumentation, you could detect and measure some gains with higher octane fuel, but as far as real world cost/benefit, I am sticking with 87 octane even when towing in the mountains.
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Old 06-27-2022, 07:21 PM   #7
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You won’t hurt it by using 87.

You may notice a difference in performance when using 89 or 91. If the engine management system can take advantage of the higher octane rating then it retards the ignition timing when using a lower octane rating fuel. Retarding the timing will typically reduce mileage as well as power.

So the best way to decide is to use both fuels under similar operating conditions. If the mileage doesn’t drop on the lower octane fuel then keep using it. If it does, then decide if the increased mileage on the higher octane fuel is enough to overcome the price premium.

If you use the higher octane fuel and can notice increased power, then decide what that is worth to you.

On a stock twin turbo 3.0 litre (not a Ford) my most economical operation was on 89. 91 resulted in noticeably more power. 94 with no ethanol made it sing.

Note that not all operating conditions require the higher octane rating. It may be that on 87, for example, the timing is retarded 5% of the time, while on 91 it is far less than that. The vast majority of your operating hours will not put the same demands on the engine as a short pull in hot weather on a steep climb with a load.
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Old 06-27-2022, 07:28 PM   #8
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Quote:
Originally Posted by Daquenzer View Post
I have burned premium while towing with my 2020 F150 and I have a 3.5 Ecoboost. Complete waste of money. I don’t see any performance change at all from 87 regular. I have also tried the mid-grade. No difference that I can perceive. And for the extra cost certainly not worth it.
Perhaps you could share your butt dyno readings as proof.

It's a simple fact that increased load and temperature increases the likelihood of pre-detonation especially in NA high compression engines and those with effective high compression like forced induction engines. Because knock sensors retard timing to (mostly) prevent pre-detonation you may not notice it, but your engine is producing less power and running less efficiently, whether you perceive this or not. If someone isn't bothered by this fact, then buying less expensive fuel is probably the way to go.

IMO, this is like other issues we discuss where people decide to ignore the manufacturer's recommendations because they feel like they know better than the engineers. I don't think Ford makes any money if someone buys premium instead of regular fuel, so they have no particular incentive to suggest 91 if it weren't more desirable. In fact, being able to use 87 when towing would be a selling point.

Ford's recommendation is consistent with other sources I've seen about the use of premium fuel in turbocharged engines, especially when under high loads, so it makes sense to me. YMMV.
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Old 06-27-2022, 07:30 PM   #9
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Quote:
Originally Posted by 1StreamDream View Post
When I first got my 25' flying cloud, I had a 2016 F-150 with the 5.0L v-8 (aka the "coyote") and I always burned regular (87 octane) in that. Now I have a 250 with the 7.3L v8 and burn 87 in that as well. Never felt like I needed higher octane, and I always said I had plenty of power with the 5.0, but the trans would do a lot of downshifting to stay in the right power band (high RPM). With the 7.3L/10sp I have an order of magnitude less downshifting, but still do get it on occasion. Primary reason to upgrade the truck was I wanted a heavier tow vehicle chassis and for me it was definitely worth it. I don't doubt that if you had enough instrumentation, you could detect and measure some gains with higher octane fuel, but as far as real world cost/benefit, I am sticking with 87 octane even when towing in the mountains.
I read on one web site where in a naturally aspirated engine that premium could actually reduce performance. Wish I had that article though. May want to search for it.
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Old 06-27-2022, 07:33 PM   #10
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I've had three F150s including a V8 a 2015 eco boost and a 2017 eco boost. I use regular gas. The computer can adjust supposedly for regular and premium but not mid grade (I was told at the dealer). I haven't heard any bad noise or knock. Every once in a while I buy premium and do some Italian takeoffs!
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Old 06-27-2022, 07:34 PM   #11
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Quote:
Originally Posted by mikeinca View Post
Perhaps you could share your butt dyno readings as proof.

It's a simple fact that increased load and temperature increases the likelihood of pre-detonation especially in NA high compression engines and those with effective high compression like forced induction engines. Because knock sensors retard timing to (mostly) prevent pre-detonation you may not notice it, but your engine is producing less power and running less efficiently, whether you perceive this or not. If someone isn't bothered by this fact, then buying less expensive fuel is probably the way to go.

IMO, this is like other issues we discuss where people decide to ignore manufacturers recommendations because they feel like they know better than the engineers. I don't think Ford makes any money if someone buys premium instead of regular fuel, so they have no particular incentive to suggest 91 if it's not needed. In fact, being able to use 87 when towing would be a selling point.

Ford's recommendation is consistent with other sources I've seen about the use of premium fuel in turbocharged engines, especially when towing so it makes sense to me. YMMV.
So what. I go a little slower. I read one article where it may reduce performance by a half second in a quarter mile start. And you might gain a 1/2 mile per gallon. If you can perceive a 1/2 second difference in a quarter mile you have tremendous internal clock. A recommendation is not a requirement. Big difference.
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Old 06-27-2022, 08:09 PM   #12
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So what. I go a little slower. I read one article where it may reduce performance by a half second in a quarter mile start. And you might gain a 1/2 mile per gallon. If you can perceive a 1/2 second difference in a quarter mile you have tremendous internal clock. A recommendation is not a requirement. Big difference.
Never said it was required and neither did Ford, just that there was a difference in engine power and efficiency. Perception is irrelevant.

Yes, the engine management system will prevent audible knocking but it's basically reactionary. The knock sensor doesn't respond until it detects some level of pre-detonation so even if you don't hear knocking it's still occurring to some extent. Maybe this isn't happening all the time but with low octane fuel on a hot day pulling a grade with your Airstream you can be pretty certain that it is.

Dealing with this issue by purchasing premium may not be worth it to some folks. That's fine. For the times that I'm towing, it would be worth it to me. Of course, since I tow with a turbo diesel, I don't have to make that decision!
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Old 06-27-2022, 10:39 PM   #13
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The sensor does not pick up just audible engine knocking, it is designed to detect high frequency vibrations that are imperceptible to the operator.

Missing out of this discussion are the other factors in modern engine design that also impact preignition, such as direct injection.

While there can be a difference in engine power and efficiency on lower octane fuel, it isn't a certainty that there will be. It depends on the actual fuel octane rating (not what it said on the pump), operating conditions, engine load, and so on. It may be that the potential for preignition is only there a small percentage of the time, most likely at full throttle. If an owner does not often drive at full throttle, it is very likely that they won't notice any difference in engine operation.

If the engine computer is retarding the timing significantly, then not only power will be reduced, but mileage. Thus, checking whether mileage is impacted is the easiest way to see if your engine, using your fuel, under the conditions you drive in, is not operating to its full potential because of fuel variations.

I don't understand the reference to not being able to adjust for midgrade. Midgrade is simply a blend of regular and premium. The engine has no way of knowing what fuel is in there, it can just tell if preignition is occurring and adjust the spark timing accordingly. I regularly used midgrade, but that was also because where I live we have high quality fuel and I knew how it responded. When travelling in areas where I didn't know the fuel suppliers, I was more likely to use premium.

This all leaves aside the other potential differences with different fuel grades. There is no difference in energy content (a common myth) but there used to be a difference in the amount of detergents that a supplier used. Premium fuels had more detergents. That isn't as common as it used to be. The biggest thing I looked for was not octane rating, but the inclusion of ethanol. I would purchase a different octane rating fuel to avoid ethanol, within reason. The 94 with no ethanol was the best fuel we could find, and was common with one brand here.
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Old 06-27-2022, 11:32 PM   #14
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The sensor does not pick up just audible engine knocking, it is designed to detect high frequency vibrations that are imperceptible to the operator.

Missing out of this discussion are the other factors in modern engine design that also impact preignition, such as direct injection.

While there can be a difference in engine power and efficiency on lower octane fuel, it isn't a certainty that there will be. It depends on the actual fuel octane rating (not what it said on the pump), operating conditions, engine load, and so on. It may be that the potential for preignition is only there a small percentage of the time, most likely at full throttle. If an owner does not often drive at full throttle, it is very likely that they won't notice any difference in engine operation.
Agree, and that was part of my point. Just because the operator doesn't perceive engine knocking doesn't mean that there isn't an issue at all.

It's true that reductions in power and efficiency as well as borderline pre-ignition from using low octane fuel in high compression or forced induction engines will only occur under certain conditions of load and temperature and those conditions may only be present for a small percentage of the time in normal driving. But when towing, they will be present relatively more often. There's really no doubt about that. Whether it's worth spending more for premium to help mitigate the problem is up to the individual owner.
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Old 06-28-2022, 05:12 AM   #15
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Originally Posted by hikingcamera View Post
I've read several debates now about octane levels in F-150s. And I guess I'm risking opening this debate here now, lol! This is what my Ford manual says:



I'm towing a Flying Cloud 23 Corner Bunk Bed (6000-lb GVWR, have not weighed it yet, on my list to do soon) with a 2021 F-150 Crew Cb Short Bed (5.5') 1808 Payload capacity, 7050 GVWR.

Should I consider using 91 octane fuel? (We currently used 87).

No, use 87. Mid grade may help you marginally but I've never seen any proof of higher octane levels being beneficial to anything other than highly tuned super-car engines like mclarens and Ferrari. "engine damage" with regular grade gas, no.

I have the twin turbo ecoboost. On occasion during previous political environments I would put a tank of mid-grade in it when I was about to pull a big mountain peak road, but now, forget it, its 150$ at regular grade now as it is.
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Old 06-28-2022, 05:36 AM   #16
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F-150 3.5 here as well - and I use 89 normally and 91 when towing. I've tried 93 and noticed no perceptible difference in performance or fuel mileage. I also only use major gasoline brands (Exxon/Mobile, Sunoco, Shell, BP/Amoco, etc.) whenever I can.
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Old 06-28-2022, 05:56 AM   #17
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What oct does Ford recommend that you use? Is that their recommendation in the first post? If so, why not follow their recommendation?
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Old 06-28-2022, 07:40 AM   #18
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For my 2018 3.5L Ecoboost I asked my dealer service department and Ford customer support and the consistent answer was 87 Octane for normal driving and 91 Octane for towing. They were also adamant that you should never go below 87 Octane even though regular in higher elevation locations (Colorado) is 85. My son-in-law is a seasoned mechanic and he said most all auto manufacturer computers now log pre detonation events and if there is an engine failure this log is used to determine warranty coverage.
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Old 06-28-2022, 08:06 AM   #19
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No, use 87. Mid grade may help you marginally but I've never seen any proof of higher octane levels being beneficial to anything other than highly tuned super-car engines like mclarens and Ferrari. "engine damage" with regular grade gas, no.
If you have a 3.5 EcoBoost designed to take advantage of premium fuel, it could make a difference. For example a F-150 Limited or my Navigator. I am skeptical it would make a difference in the similar engine designed to operate on regular fuel.

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Old 06-28-2022, 08:23 AM   #20
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What oct does Ford recommend that you use? Is that their recommendation in the first post? If so, why not follow their recommendation?
It’s called cost benefit analysis. Does the extra cost of running premium add more value to offset that cost?

Maybe it some situations it does, and in others it doesn’t.
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