Regular or Premium Gas

[Unsta]

Really? Has this changed since Ethanol gas first came in?

I thoguht when the ethanol bandwagon started the supreme was exempt and that's partly why they recommend 91 octane now for small engines since they're not made to handle the ethanol.

Maybe my mileage benefits are just in my head?

 

[peterk9]

That might have been the case prior to the gov't mandate. I've always run 87 in my mowers and snowblower. I just hope that they don't raise the percentage.

Peter

 

[Bill #5 Explorer]

I'd bet you had a tank of bad gas. That's why you got some pinging. Then you added good 89 and saw/heard the improvement. Anything over 87 octane is a waste. The engine can't use the additional octane. It's not bad for the engine, just for your wallet. The other way around can prove bad for both (using 87 octane when the engine calls for 93, for example).

Yes, getting a fuel without alcohol will have benefits (raise mpg's). I use 91 octane without alcohol whenever I can get it in upper Wisconsin and lower Minnesota.

 

[BMan5150]

With all due respect from the various replies...

There is no "octane sensor" that measures octane and reports it back to the ecu. There are knock sensors. If the engine "hears" knock, it will retard ignition timing advance to try to eliminate excessive pinging or knock. If you run higher octane in an engine designed to run on 87 that has a knock sensor (all new cars do now but some not too old cars don't have knock sensors) it will make slightly more power than when running 87.

I have been told by various mechanics that modest pinging when first stabbing the throttle is harmless. I believe this to be true, but it drives me nuts. I had a 2001 ford mustang gt with the 4.6L SOHC v8 that pinged like crazy on 87 even when brand new when I accelerated even slightly quickly. Techs determined it was "normal" operation...at first I didn't believe them as "the manual states it is designed to run on 87 octane." I quickly grew tired of hearing pinging so I just started putting 91 in. No more pinging. The one thing different though about this car/motor is that it did not have a knock sensor (only the cobra 4v dohc modular v8 had knock sensors) so me putting 91 octane in it didn't make one bit of extra horsepower. In this case, all I was doing was raising the octane to stop the pinging. 48 drag strip passes and 98,000 miles later the car was still running strong and not eating any oil when I traded it in.

If the truck isn't pinging like crazy on 87 and /or any light pinging isn't bothering you, your best bet is to keep running 87. If the pinging bothers you; or you run the truck really hard all the time; or you tow a lot, then you should run 91 octane gas.

Again, not trying to disrespect anyone here...just wanted to share my thoughts on the matter. I've wrenched on a bunch of cars but I'm no mechanic. I've just learned enough about cars and tuning to be dangerous!

 

[stillmarried]

Cost per mile calculation on a 3.5 liter NA engine: I came up with the cost per mile for each grade of gas over a years time, however I did not count the first 3,000 miles since the cost during break in period seemed to level off after the first 3,000 miles on the odometer.
Regular grade cost 10.8 cents per mile.
Medium grade cost 11.6 cents per mile.
Premium grade cost 11.4 cents per mile.
One variable that I was stuck on is what affect the summer vs winter blends of gas would have on the outcome, but since the calculations were for a year, I may have balanced it out.
So, if you buy medium grade gas for 200 miles of driving, and I buy regular grade gas for the same 200 miles, I will save $1.60 that trip, ($0.116 - $0.108) = $0.008 savings per mile multiplied by 200 miles = $1.60 savings. Not a staggering savings, but I will take it. Once in a while I will run a tank of premium grade gas, but overall I will grab the regular grade when I need gas from now on.

 

[peterk9]

Keep in mind that costs for drivers would differ depending on the type of driving they do and their driving style. Burning Premium in a NA V6 engine does nothing for it. If regular 87 octane is recommended, anything else is really just a waste of $$ in that engine. I use 87 in my V6 3.5L Ecoboost after using 91 since I didn't see the benefit of running anything higher in the type of driving I do. I think the current cost difference here between 87 and 94 is about 56 to 60 cents an Imperial gallon.

Peter

 

[613GT500]

The gas station that I fill up has 0% ethanol on 91 (as only 87 and 89 is labled as contaning up to 10% ethanol).
The difference is negligible, at an extra $0.15/L and it is required for the 3.5EB, if you want anything close to the advertised hp/tq output.

I own 3 vehicles and they all use premium only.

 

[Napalm]

All modern engines have sensors that detect octane level and will adjust engine parameters accordingly.

no they do not.

or let me be a touch more specific - almost no car on the road today has an OCTANE sensor. There are a few that have sensors that determine E60-E85 fuel vs standard gasoline, but that is not Octane. It is determined by specific gravity of the fluid and can only distinguish between mostly ethanol fuel vs most gasoline fuel.
almost all flex fuel labeled cars have some flavor of this sensor.

Now - there is in most computer controlled engines - based on temps, and knock vibration - algorithim's that will change the spark timing due to issues is ping.

So I will add to this for the Op something else. if you have over 100K on the clock and you haven't changed your spark plugs then no it won' t matter what fuel you use.

But - the 3.5 TI-VCT motor will change the cam and spark timing slightly due to temps, pre detonation events, and other parameters. Such that it will indeed make more power, and/or use less fuel under some conditions with 93 octane gas vs say 87.

Therefore going 87 to 89 is just about useless - it's not that far off the mark. but in the southeast US you will find 93 octane, or more specifically 91+. The computer will take advantage of that but usually it will take about 1/2 a tank full to see that changes. I have found on my explorer - when the outside air temps are over 90 for most of the day - and the humidity is fairly high - I do indeed get 1-3mpg more using 93 octane than I do using the standard 87.

My other car is tuned to only use 91+ octane so that's all it gets.

 

[peterk9]

Hot weather and humidity alone will provide somewhat better mpg but it is usually offset by using the A/C.

Peter

 

[Napalm]

usually as it get hotter the mpg will go down - once out near 100F the likely hood of predetonation goes up - since compressing the air and fuel mix will make it even hotter.

so often with weaker octane ratings in the summer in the deep south the computer tends to lower the spark timing. And in some cases mods the cam timing also. the only car I have owned that didn't benefit from running 93 octane when the temps stay above 95 was our 2012 ford focus and even that I could argue gained about 1mpg. I think the key there was the Direct injection.

 

[reserved50]

You shouldn't have a problem running 87 octane, bad gas? I would put in the highest octane you have available and a concentrated fuel injector such as Chevrons in the tank, you will have to use that little funnel Ford supplied that's in the spare tire area. Then drive it hard up to the speed limit allowing it to reach higher rpms (easiest way without reaching high speeds is climbing steep roads). If you have any carbon build up this should remove some and then switch back to 87 .

 

[peterk9]

usually as it get hotter the mpg will go down - once out near 100F the likely hood of predetonation goes up - since compressing the air and fuel mix will make it even hotter.

so often with weaker octane ratings in the summer in the deep south the computer tends to lower the spark timing. And in some cases mods the cam timing also. the only car I have owned that didn't benefit from running 93 octane when the temps stay above 95 was our 2012 ford focus and even that I could argue gained about 1mpg. I think the key there was the Direct injection.

When the air is hotter, the engine warms up quicker and reaches operating temperature faster. Hotter air is also less dense which reduces the friction of the air flow over the vehicle. The Internet says so and everyone knows what's on the Internet is true.
https://www.fueleconomy.gov/feg/hotweather.shtml

Peter

 

[Flatplane]

So when hotter air being less dense reduces the friction of airflow over the vehicle, it follows that the hotter air will flow better into the engine allowing better performance. Is that correct?
I was under the impression that the hotter less dense air would not allow the air/fuel mixture to reach adequate levels for enhanced performance. It follows that turbocharging will increase the amount of air entering the engine allowing the fuel to be increased in that ratio to provide better performance.
Be careful what you state on the internet as it can be misquoted!

 

[MikB]

From the owners manual:

Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is
recommended. Some stations offer fuels posted as “Regular” with an
octane rating below 87, particularly in high altitude areas. Fuels with
octane levels below 87 are not recommended. Premium fuel will provide
improved performance and is recommended for severe duty usage such
as trailer tow.

I use 92 octane exclusively in my Ex and don't believe it's a waste of money to do so. If I still worked, I'd probably have a different attitude.

Oh, by the way, I also had the same problem with pinging in my '01 Bullitt using 87 and went straight to 92. Problem solved. Also, no amount of pinging is good for any engine and should never be considered 'normal'. JMO

 

[snomas]

I was getting a light bit of pinging running 87 fuel for the last while, nothing crazy, just a small bit under initial throttle input. I've been running 87 octane for 120k kilometers on my 2012 V6 Explorer.

I put in a full tank of 89 octane a few days ago (we basically have 87,89, and 91 fuel choices), and thus far the pinging has not returned. It seems like my fuel economy is a bit better, but it may be too early to tell. Does anyone think there are benefits to running a higher octane in these vehicles ?. I've got a long road trip coming up soon through the southern US and I don't mind going up to 89 octane if there are benefits to running it - hot summer conditions with A/C operation and a fully loaded truck through some mountainous terrain.

I disconnected my battery to clean the battery posts as part of my pre-trip maintenance, so the ecm may have been re-set, not sure if that is good or bad but I just wanted to throw that into the post. Thanks for any replies and thanks for reading.

I live in Colorado and I use 85 octane and have never heard a ping.

 

[reserved50]

the person that started this thread didn't mention any change of driving habits, altitude or towing etc. That's why I figured it needed maintenance or had bad fuel in it.

I live in Colorado and I use 85 octane and have never heard a ping.

 

[1995E]

How do you know your engine is pinging? I use 87 and my engine's performance seems to change off between powerful and weak sometimes.

 

[ExPlat]

I read other Ford Forums and the quote below is from a very knowledgeable Ford employee who is respected for his insight to Ford's engineering process. From this statement I can see that 87 octane is all the Ex needs, but not all it can use.

This was the 5th post on a Flex Forum thread about gas/octane.
"Unless your Ford specifically says "Premium required", it means it was tested and passed all it's requirements using 87 octane. However over the last 6-7 years, Ford has begun using an active method of "searching" for higher octane. 10 years ago the knock sensors were passive and would just retard as needed, but now there is an algorithm that will occasionally advance the timing to see what happens. If everything is good, it will advance a bit more and eventually you end running the engine in an optimal fashion for the premium fuel that you have put in. So while 10 years ago putting premium into an otherwise perfectly running engine didn't make any difference, that's no longer true. Your Flex will take advantage of the premium, though it's still true that the benefits are not likely worth the premium cost, unless you're looking for optimal performance. On the EB, regular fuel will cost you around 20-25hp."