Mixing regular and premium gas

[Joel B]

I have never heard about using premium prior to now. I’ve never run anything but regular.
news to me…

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[ryde4ever]

One other thing to consider with using higher octane fuels. Many name brands, Shell, BP, Amoco put more detergents in the higher octane. The additional detergents help keep injectors and combustion area cleaner, less carbon. I have tried all 3 levels of octane. I get a little better performance and mpg with the premium. And I try to always use Top Tier gas or name brand gas, premium with each.

 

[MakinDoForNow]

When possible I like to use ethanol free fuel because you get 3 to 7% more mileage out of it at Any octane ethanol tend to lower your mileage and also evaporates more quickly so in odd places like Phoenix, you lose a little bit all the time. Here is a list of ethanol, free gas stations some states that have many some states have none.
https://www.pure-gas.org/

And only cost 16% more!

 

[Meeka]

I see a world of difference between 87 and 93 octane in my ecoboost. I was very surprised by the difference and won't be going back. It's worth the extra $ for me to have the truck run much better and not have to worry about as much carbon build up.

Pardon my ignorance here people, but why does a higher octane rating reduce carbon build up? I’m kinda thinking because of the extra additives or ‘cleaning agents’. That’s why it cost more per litre, or gallon. I’m guessing it’ll benefit my 24 Eco. Choices here, 87,89,91,94. I’m retired, ain’t gonna use 94.

 

[Blue_Max]

I have never heard about using premium prior to now. I’ve never run anything but regular.
news to me…

The owner's manual says the engine is tuned to run best on 91 octane, but 87 octane is the minimum.

 

[SubtlySeismic]

Pardon my ignorance here people, but why does a higher octane rating reduce carbon build up? I’m kinda thinking because of the extra additives or ‘cleaning agents’. That’s why it cost more per litre, or gallon. I’m guessing it’ll benefit my 24 Eco. Choices here, 87,89,91,94. I’m retired, ain’t gonna use 94.

I have nothing more than bro science to back that claim up maybe it's all marketing, but the typical brands make bold claims on their top tier gas that I assume is related to detergents/additives. The variable timing of our trucks should make the octane rating irrelevant with carbon build up.

 

[Toddman45]

I've always used 87 in all 4 of my EcoBoost trucks and cars. Never had a single fuel issue the entire 14 years

 

[Paulyz]

I know it is ok to use regular gas, but it says in owner manual that in the summer you may have to use premium. My thought is to alternate between the two at fill ups. Thoughts?

I've had my 2022 ecoboost XLT AWD for 2 years now and I only used premium gasoline one time. Didn't notice any difference. My truck is very quick & responsive. Only time I'll use premium is when towing.

 

[dn325ci]

I have nothing more than bro science to back that claim up maybe it's all marketing, but the typical brands make bold claims on their top tier gas that I assume is related to detergents/additives. The variable timing of our trucks should make the octane rating irrelevant with carbon build up.

The octane difference makes no difference in carbon build up. Shell's long running advertising of their branded premium "V-Power" grade made that claim, but the only truth in the claim came because Shell did not use their better detergent additives in their own lower grade gasolines, so the claim was made that the premium V-Power created cleaner engines. It literally has nothing to do with octane, and everything to do with the additives.

So "Top Tier" or higher detergent gasolines do make a difference, though the difference on direct injection engines is diminished considerably from the reporting I've read. You do not need to buy 91/93 octane to get Top Tier gasoline. I buy gas at Costco, and both grades they sell are Top Tier rated.

 

[dochawk]

it actually is linear, but you can't really know how much gas is currently in your tank until after you've filled it full.

I don't mean for the tank, but for the amount added.

It's beyond my own knowledge, but there were a couple of threads on the companion f-150 forum that went far more in-depth than I'd ever want to know (nd I have a Ph.D. jointly in Economics & Statistics!). Anyway, none of them disputed the non-linear octane rating. Between my economics and my physics, a nonlinear response to something whose value adds linearly doesn't even vaguely surprise me, but I'll defer to those who spend their time with it.

Anyway, the base is upward of the mean, so you wouldn't be risking anything using the linear average.

hen I am over 3500 altitude I may buy 1/3 88 to the 86 regular sold there particularly if I am headed back to my 1100 altitude 87 area.

less octane is needed in the lower pressure air at higher altitude; the range of three octanes tends to drop together as you climb.

In most Gas Stations Regular and Midrange are both Midrange.
So just use "Regular" and your will be fine.

I can say with certainty that several years ago, regular and midrange at ArCO in Las Vegas were different. My Miata said premium, i accidentally put in regular (long habit), and it just sagged when I gunned it in an emergency maneuver. Further testing showed that mid grade didn't have this problem.

I have never heard about using premium prior to now. I’ve never run anything but regular.

I haven't seen anything to suggest that the hybrid 2.5 will adjust anything to take advantage of the extra octane.

Many name brands, Shell, BP, Amoco put more detergents in the higher octane.

That used to be the case pretty much across the board; premium had the detergents and the extra octane.

These days, I don't believe that any Top Tier uses less in their regular than the premium.

Pardon my ignorance here people, but why does a higher octane rating reduce carbon build up? I’m kinda thinking because of the extra additives or ‘cleaning agents’.

Encouraging harder driving?


One of the engineers from the Northstar, one of the first generation engines that relied on Top Tier, states that it should taken from zero to freeway speed at full throttle at least once a month--it turned out to be subject to carbon buildup, and they hadn't really considered the possibility that people would drive it like grandmas!

 

[SubtlySeismic]

The octane difference makes no difference in carbon build up. Shell's long running advertising of their branded premium "V-Power" grade made that claim, but the only truth in the claim came because Shell did not use their better detergent additives in their own lower grade gasolines, so the claim was made that the premium V-Power created cleaner engines. It literally has nothing to do with octane, and everything to do with the additives.

So "Top Tier" or higher detergent gasolines do make a difference, though the difference on direct injection engines is diminished considerably from the reporting I've read. You do not need to buy 91/93 octane to get Top Tier gasoline. I buy gas at Costco, and both grades they sell are Top Tier rated.

That's a lot of words to basically agree with me . Good to know about costco. Never looked into it.

 

[dn325ci]

The owner's manual says the engine is tuned to run best on 91 octane, but 87 octane is the minimum.

From the Owners Manual:
"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. "

The wording Ford uses here is similar to other manufacturers now tuning for both 87 and 91/93. I have a 2023 Mazda Miata with similar wording, though slightly clearer that the benefit is a power benefit, not a reliability benefit.

So I wouldn't say it's "tuned best" for 91. Again, it's not a reliability benefit, it's a power benefit. The truth is if you run premium the sensors and processing will advance timing and boost a bit resulting in about 10% power increase for Ecoboost.

Who doesn't love more power, right? You have to decide if the power increase is worth it. I've been going back and forth on this a lot recently because I've been testing the improvements of the Cobb Accessport off-the-shelf programs for 87 vs. 93.

Bottom line for me is I don't find that I use the 10% power increase very much in my daily driving. Maybe I would in the summer time more. I don't believe the occasional benefit is worth the constant 40-50% price premium that 91/93 is selling for at this time.

EDIT: Gassed up tonight: Costco regular at 2.64 and premium at 3.69. 1.05 more or about 40%.

 

[The Real Maverick]

I have no expertise, but I was talking to my mechanic friend about this. His recommendation was to not use higher octane but acknowledged that it will give some extra HP. He was, however, adamite about not switching.

He said pick one octane and stick with it. He said he has had engines in the past that had issues from the constant timing changes from octane switching. He said the newer engines might not have the problem, but he doesn't know and wouldn't want to test it on a new engine.

Occasional switching like twice a year for the seasons probably wouldn't be bad. Every other tank seems excessive when you could just use midgrade all the time.

I agree, pick one and stick with it.

You can of course use any.

But it takes the truck about 100 miles to fully adjust to the change, and it needs to experience the whole power band. For example, if you switch and then do 100 miles of exactly 65 MPH on cruise control without variable gradients, it will only "retune" for that condition and will need additional time to adjust to city stop n go driving.

 

[The Real Maverick]

One other thing to consider with using higher octane fuels. Many name brands, Shell, BP, Amoco put more detergents in the higher octane. The additional detergents help keep injectors and combustion area cleaner, less carbon. I have tried all 3 levels of octane. I get a little better performance and mpg with the premium. And I try to always use Top Tier gas or name brand gas, premium with each.

Ever hear of the very powerful placebo additive? The effects of placebo is guaranteed to give added horsepower and torque.

 

[The Real Maverick]

When possible I like to use ethanol free fuel because you get 3 to 7% more mileage out of it at Any octane ethanol tend to lower your mileage and also evaporates more quickly so in odd places like Phoenix, you lose a little bit all the time. Here is a list of ethanol, free gas stations some states that have many some states have none.
https://www.pure-gas.org/

Gasoline has a vapor pressure of about 10.

Ethanol has a vapor pressure of about 2.

Gasoline evaporates 5 times faster than ethanol. (At equivalent temperature.)

Some people are confused by the fact that a gasoline & ethanol mixture can technically have more evaporative emissions, but only because you are evaporating two substances at once. But ethanol evaporates much less than gasoline. When cold, it vaporizes so little, and eventually not at all, so makes it hard to start your car in sub-zero conditions.

Therefore, E85 is only 70% ethanol at higher latitudes - the 30% gasoline is good for cold weather starting.

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