2018 GT MPG 87 vs. 93 octane

[WildHorse]

91 octane isn't required. 93 octane isn't required.

Yes it is, as I stated earlier. Do you understand what "severe duty usage" in automotive terms are? and it has nothing to do with racing. Well a little.

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[Bikeman315]

Yes it is, as I stated earlier. Do you understand what "severe duty usage" in automotive terms are? and it has nothing to do with racing. Well a little.

Sorry Coyote but that is just not true.

From fueleconomy.gov

Will using a higher octane fuel than required improve fuel economy or performance?
It depends. For most vehicles, higher octane fuel may improve performance and gas mileage and reduce carbon dioxide (CO2) emissions by a few percent during severe duty operation, such as towing a trailer or carrying heavy loads, especially in hot weather. However, under normal driving conditions, you may get little to no benefit.

My Jag clearly stated that it required 91 as did my Infiniti. My Mustang says no such thing. The word “required isn’t used at all. The word “recommended” is used for premium gas.

Now my choice for daily driving is 93. Why? Honestly I’m old school and agree with your compression argument. Yeah probably could save a few bucks buying 87 put I can afford it.

 

[millhouse]

Yes it is, as I stated earlier. Do you understand what "severe duty usage" in automotive terms are? and it has nothing to do with racing. Well a little.

Racing is severe duty. Towing is severe duty. Daily driving is not.

 

[WildHorse]

Daily driving is not

If you say so

 

[torqued]

Racing is severe duty. Towing is severe duty. Daily driving is not.

Maybe that depends on how you daily drive it. I certainly didn't get this beast to drive it like a Camry.

 

[Tseg]

Racing is severe duty. Towing is severe duty. Daily driving is not.

Idling is about the most severe duty, also short trips and turning off engine before properly warmed.

 

[millhouse]

Maybe that depends on how you daily drive it. I certainly didn't get this beast to drive it like a Camry.

Do you operate in a constant state of high load conditions as seen in towing and racing? We both know this is a firm no.

Idling is about the most severe duty, also short trips and turning off engine before properly warmed.

This is a different type of severe duty that has no bearing in regards to octane. You’re talking about hours vs miles.

 

[Qcman17]

This is a good thread I've learned I am either wasting my money on 91+ or am going to ventilate the block on 87 LOL.

 

[Zooks527]

The unstated assumption in all of these is "in a clean engine".

Assuming the engine is clean and unmodified, there's no economic benefit to using higher octane levels (you'll never get the cost differential back in improved mileage) and likely little to no performance benefit on public roads at legal or moderately illegal speeds.

Add a bit of hot carbon to the mix and things can go a bit off. Carbon based detonation is harder to control with knock sensors and under some conditions (lugging the engine down comes to mind) may not be able to be avoided even with added knock sensors.

So, post-2018 with the dual-fuel path keeping the valves clean, you're likely fine with good quality 87 (major manufacturers with more-than-minimum detergents). Using the cheapest 87 you can find from a station you never heard of before? There could be some issues.

Same thing if you've got an engine that's burning some oil. You could get carbon buildup in a cylinder, and the detergent levels in any gasoline may not help. In that case, a bit more headroom before detonation with a higher octane level could be advantageous.

 

[OldPhart]

Hi - I would think or hope (no guarantee) that from a liability cost basis FORD would come out with a warning or edict regarding an octane requirement change if engine problems were occurring related to low octane gas usage. Until a change you should be able to rely on their guidelines. Other than that we’re back to the the usual preference decision. From what I’ve seen on this forum, depending on where you live, different octanes are available. Here in western NY we have regular 87, mid grade 89, premium 93 and non-ethanol 90. Our ethanol content is 10% (they say up to 10%). We have very little E-85 available, at least in this area. My car is only a summer seasonal car that will probably get around 5000 miles per year on it and I use top tier 93 Octane. Any extra performance is meaningless to me. I just feel better and safer about using it even though my feelings have no scientific basis. I plan to keep the car for many years and I’m just playing the odds that it could make a difference long term. The person who said the cost is a judgement thing is correct for most of us. If we want a performance car that cost $50G we likely don’t need to worry about the cost difference of gas, but that doesn’t mean we don’t care. It’s the same with mpg. We shouldn’t be overly concerned about that, particularly someone like me who puts minimum annual milage on it, but it sure feels good psychologically to be able to say I get close to 30 mpg on a trip. Me, I take my car off the road and surrender the plates for about 5 months while keeping only the comprehensive coverage. NYS law requires us to remove the plates if we don’t have liability coverage. That saves me about $400 per year. Does it really impact my finances? No, but psychologically I feel good about saving $400. I buy jeans at BJ’s for $14 instead of $34 at LL Bean. It’s these type of discussions that keep the forum entertaining as long as they don’t get nasty or too far off base like talking about the price of jeans. So, as they say, pick your poison... Bruce

 

[Dfeeds]

and likely little to no performance benefit on public roads at legal or moderately illegal speeds.

Not necessarily true. The benefit of higher octane in an engine like the gen 3 is to utilize the higher compression which is too much for 87 octane, even with the controlled snd cooler charge of DI. The VCT system will retard the cam timing to effectively reduce the compression ratio and allow 87 octane to be used. This won't have a noticeable impact on peak HP but it will impact your low end torque. This is where most daily drivers live and where most of the seat of your pants feeling comes from. This is one of the reasons why e85 people feel such a noticeable difference.

 

[Coosawjack]

Why buy a $50K plus car and even consider low octane fuel??

 

[Bikeman315]

Hi - I would think or hope (no guarantee) that from a liability cost basis FORD would come out with a warning or edict regarding an octane requirement change if engine problems were occurring related to low octane gas usage. Until a change you should be able to rely on their guidelines. Other than that we’re back the the usual preference decision. From what I’ve seen on this forum, depending on where you live, different octanes are available Here in western NY we have regular 87, mid grade 89, premium 93 and non-ethanol 90. Our ethanol content is 10% (they say up to 10%). We have very little E-85 available, at least in this area. My car is only a summer seasonal car that will probably get around 5000 miles per year on it and I use top tier 93 Octane. Any extra performance is meaningless to me. I just feel better and safer about using it even though my feelings have no scientific basis. I plan to keep the car for many years and I’m just playing the odds that it could make a difference long term. The person who said the cost is a judgement thing is correct for most of us. If we want a performance car that cost $50G we likely don’t need to worry about the cost difference of gas, but that doesn’t mean we don’t care. It’s the same with mpg. We shouldn’t be overly concerned about that, particularly someone like me who puts minimum annual milage on it, but it sure feels good psychologically if we can say we get close to 30 mpg on a trip. Me, I take my car off the road and surrender the plates for about 5 months while keeping only the comprehensive coverage. NYS law requires us to remove the plates if we don’t have liability coverage. That saves me about $400 per year. Does it really impact my finances? No, but psychologically I feel good about saving $400. I buy jeans at BJ’s for $14 instead of $34 at LL Bean. It’s these type of discussions that keep the forum entertaining as long as they don’t get nasty or too far off base like talking about the price of jeans. So, as they say, pick your poison... Bruce

My pick for most intelligent post of the year.

 

[Bikeman315]

Why buy a $50K plus car and even consider low octane fuel??

Didn’t you know us rich folks are also the cheapest? How do you think we got rich?

Public Service Message......the laughing emojis mean I’m kidding.

 

[Dfeeds]

My friend religiously uses the cheapest gas but spends $100+ at the bar every weekend. That logic am I right?

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