High test gas in car

[xs11jack]

I am thinking of buying a Toyota with a 3.5 V-6 with a 10 to 1 compression ratio, will I need to use 91 or higher octane gas in it?
Ole Jack

[Mica_Hiebert]

allot of variables such as ignition timing and elevation come into play but my guess would be yes but also depends on your driving... my 97 & 98 f150 with 4.6 liter pinged horribly when pulling hills on the highway at around 2500 ish ft elevation but never noticed it otherwise and never cold bring my self to pay for premium gas.

[brtelec]

I do not know if it will affect your vehicle the same way, but when I bought my wife's car I was told to run nothing but 91 plus in it. You can hear it pinging at hard acceleration, but the biggest difference is the car gets 3 miles to the gallon better mileage on average with 91 and up. I asked the tech about it and he said the cars computer makes changes to compensate for the lower octane fuel and mileage suffers from it. I thought "no way". I have messed around with it numerous times and if I run regular or plus in it, the difference in mileage will be 2 to 4 MPG worse.

[Gofaaast]

Most newer automobiles are 10.5 to 1 and run fine on good ol 87. If you can get gas that is ethanol free you will get better mileage. I am not sure what the show me state has for laws regarding whether it has to be marked at the pump if it has 10% ethanol blend or not. Test it yourself if you can get both and see if you come out ahead paying a little more for 100% petroleum gas. Right now ethanol costs more than gas so 100% petro should be cheaper, but I doubt it.

[Beef15]

Knock sensor will let you get away with lower than ideal grade fuel. It will make less power and get worse mileage IF it should actually have a higher octane. The ECM does this by remapping the ignition and fuel. There is a point where you may exceed the systems' ability to compensate and experience some pinging/knocking, sounds like shaking marbles/bearings/rocks in a coffee can, most common in high heat and/or hard accel, climb, or pull, it is not a good thing too much will destroy an engine. Is 91 or higher worth it, maybe.

[leadman]

Best thing to do is find the owners manual for the vehicle and read what is recommended by the manufacturer. That said all of the gasoline powdered vehicles used by the City of Phoenix were/are run on low octane fuel. The only time this varied was when we first went to gasohol and the Police Kawasaki motorcycles did not like our fuel. The officers got cards to go to commercial stations for high octane. This was in the early 90s'. The newer bikes run fine on the low octane stuff.
The computer systems on the newer vehicles control several engine systems to allow the vehicle to run on low octane fuel. Not saying you will get the best mileage but this is something you can determine by driving it. Flex Fuel vehicles normally get pretty dismal fuel mileage on the alcohol rich fuels.
About the only time I can remember a complaint of an engine pinging when I supervised a City shop was a couple of late 80s GM products that had built up carbon in the combustion chambers. The GM top engine cleaner took care of this.

[MT Gianni]

Do what the MFG says. Our old Outback fouled plugs on less then 88 Octane and mileage was 1-2 mpg greater as well.

[RogerDat]

Ethanol has less energy per volume so lower mileage than all gasoline, question is will the cost per mile work out better on straight gasoline or an ethanol blend. That depends on how well the vehicle uses the ethanol blend and what the price difference is between it and straight gasoline. This article says expect between 3-5 percent less MPG so if the ethanol more than 5% cheaper.... https://www.fueleconomy.gov/feg/ethanol.shtml

I will say if you have an older car that has never had ethanol blend you can get a situation where the alcohol cleans out years worth of varnish or deposits gasoline won't dissolve and it all goes into the fuel filter.

Ethanol actually increases octane, which is a measure of a fuels resistance to flashing/exploding which is what ping is caused by. Back when it first came out a trick I used in my old Triumph motorcycle with high compression was to buy 1/2 premium fuel at 92 octane and 1/2 ethanol regular. The resulting octane was higher than the premium alone. It was that or "detune" the ignition timing until it did not kick back when trying to start it. I liked having the high octane better :-)

Much better. :bigsmyl2:

[white eagle]

I have found that if you can find premium without ethanol
you will have it last longer that a blend w/ethanol
I use premium w/o for all my small engines in saws and the like
while on the subject of gas when did it become such a valued commodity
that you need to prepay before you can pump?
I understand the drive off's but why should everyone have to pay for it ?

[PbHurler]

While on the subject of gas when did it become such a valued commodity
that you need to prepay before you can pump?
I understand the drive off's but why should everyone have to pay for it ?

Because the needs of the many are outweighed by the deeds of a few. (sign of the times, unfortunately)

[historicfirearms]

Prepay is getting more common in central Michigan where I live too. It sure is frustrating when you want to pay with cash and want to top off. Two trips waiting in line while people buy smokes and lotto tickets... Not a great way to start your day.

[Lloyd Smale]

lower octane fuel has more energy then higher octane fuel. Octane is a burn suppressor. It keeps the fuel from being more volatile. Spark knock is caused by fuel being so volatile that compression alone causes it to ignite before its suppose to. Using the lowest octane fuel your engine will tolerate without preignition will give you the best performance as to gas milage and easy starting ect. Your computer controlled motor was designed to run on 87 octane (at least most of them) and using premium is just throwing away good money. Most gas milage increases people rave about using premium come from either a computer or motor that is made to run higher octane or because joe blow gets 16 mpg in his truck and wants to know if premium helps so he fills his tank and mentally starts driving to save fuel. Some (rare) computer controlled motors run programs that will allow for more advance in timing when they sense higher octane fuels and give slightly better mileage but its very rare that it actually pays dividends in cost per mile over regular. think of it logically. Car manufactures have to meet gas mileage standards and if they could tune all cars to run more economically on premium regular gas would have disappeared long ago. Another reason you may find you get better mileage with premium is alcohol. Most gas grades have it. Its a cheap way to get octane . Now if you compare regular with alcohol to premium without it your probably going to get better mileage with the premium. But to see that you defineately need to make sure your premium isn't getting its higher octane reading by using alcohol too. Most all 93 octane fuel has alcohol so look for 91 octane and look on the pump for a sticker that says alcohol free. Not many around anymore but they can be found.

[bob208]

best thing to do is ask the dealer. and get it in writing that way if there is a problem you could go back on them.

[dragon813gt]

The vehicle will state on the gas cap or on the inside of the gas door if it requires premium. Modern engine management will allow it to run on a lower grade fuel. It will just detune and you will have less performance.

Is prepay for gas a new thing in parts of the country? I started driving in the mid 90s and it's always been that way here. Guess it shows how regional things are. But I remember my parents having the prepay when I was a kid so it's been here for a long time.

[AK Caster]

One more point. The higher the elevation the lower the octane can be. If you drive through Colorado you will see that 85 is their "regular".

[MT Gianni]

85 is the regular in MT as well. What gets me is midgrade used to be 10 cents more then 15 cents now 20 or more. It was not related to anything other than the cost of the product. I have seen as much as 60 cents difference between regular and premium, what does it run in your area?

[rockrat]

I have been seeing it around 50 cents, reg. vs premium. I think it only costs 8 cents difference to make. Companies are making a killing off selling premium

[jcwit]

Prepay is getting more common in central Michigan where I live too. It sure is frustrating when you want to pay with cash and want to top off. Two trips waiting in line while people buy smokes and lotto tickets... Not a great way to start your day.

This is why I have a credit card which is tied to a seperate checking account with only a small amount in it. Most there is ever in it is $150 bucks, most that can be bought with the credit card is $150 bucks of anything.

No more running into a gas station for me and it's safe at least safe up to the balance in the checking account. Not enough to have any effect on the way I live for sure.

Really amazes me that more folks do not do this. I haven't been inside a gas station for years.

[reddog81]

One thing to note is that in some states there is no labeling requirement on ethanol pumps. In MO you could be buying E10 gas one day and regular gas the next day without anyway to know other than asking the clerk who probably has no idea either.
i put premium in my car if the spread is less than $.50. If the spread is more I go with regular and I try to avoid ethanol. Thankfully in Iowa the pumps have to be labeled. I have never noticed a difference in my 2006 mercedes

[dragon813gt]

Pumps are labeled here. They all add ethanol. I know of no nonethanol gas at a gas station. I can go to the track and buy race fuel. But it's cheaper to buy it by the can from a local vendor.

[RogerDat]

Gas station has a fairly thin margin on gas, when a full tank can run $50 or more that is a significant loss. Catching a drive off from the pump is seldom possible. If you get the license plate maybe you have a shot but it is not like the police are going to spend the night looking for the car or owner as if they robbed a bank. Some of the big chains don't require pre-pay because they have camera systems, smaller independent stations don't so they do pre-pay.

Man am I feeling old, I can recall when the guy came out and pumped your gas, cleaned the windshield and checked your oil. Had a pour spout that stabbed into an actual can of oil too.
Mostly gone by the time I was old enough to drive but back when I was a kid a stop at a gas station was a real production number.
You can trust your car to the man that wears the star.... Smile if you recall that ad. Your not senile if you can recall the company name!

Funny thing (slightly related) some high school kid accidentally swiped his drivers license through the pay-at-the-pump reader. It worked! He was excited to find that you could just fake pay so he told two friends, and they told two friends. Never crossed their mind that it was not only reading the license but storing the information with the sale. About 135 high school students found themselves in front of a judge with no sense of humor, caught some flack for giving some of the older ones jail time. His answer was they went there to steal, they did steal, I see no problem putting thieves into jail.

The other was a drive off after filling up a custom pickup truck, took off out the driveway and turned down a side road and was gone, next minute a county sheriff pulled in. Clerk told him about the drive off could describe the truck & it's decals, even had a partial plate. Officer gets his coffee in no particular hurry while the clerk became more agitated at the delay. Sheriff explained that road is a dead end with no side roads more than two houses long. Truck ain't going anyplace but back here. I'll catch him on his way out, which he did.

[10x]

The answer is in the cost of fuel per mile traveled.
I have a 2011 Toyota tundra that really likes Chevron Premium with Techron. The increase in gas millage that I get from using non ethanol premium offsets the apparent savings from buying a lower grade of gasoline.
I have kept track of mileage with every tank of gas since I purchased my Tundra. On the highway I can travel 1200 km on 149 liters of Chevron Premium. Using the "cheap gas" the same trip (Terrace B.C. to Peace River Alberta) will take over 200 litres of fuel. The nearest Chevron station is over 200 miles away.
Not all premium fuels are the same, some are not as premium as the octane rating suggests.
and in my Tundra a 5% ethanol content drops mileage by 7% on average (on the highway).

On another note when I drive this truck on the highway I get 12.5 litres per hundred (average), my wife will get 17 liters per hundred doing the same route and using the same gas. Driving habits determine your mileage.

I have noticed that poor gas will give ping and engine noise under lugging load - yes the computer in the tundra will let the engine lug if you are light enough on the gas pedal.
And cruise control will drop gas mileage in this vehicle by 10% or more because it will downshift.

Your engine is a pump, the faster it runs the more air and fuel pumps through it. Buy good fuel, keep the revs down, (keep it from downshifting) and you too can get good mileage.

The only way you will know for sure is to keep track of every time you flll up and work out the mileage.

My wifes Toyota highlander gets the same mileage no matter what gas we put in it.

My 94 Chev van really liked low octane without ethanol It got up to 22 mpg. Put gas with ethanol in the beast and mileage would drop to 17 mpg or less.
My 83 Dodge with 318 got 12 MPG from the factory. A back yard mechanic rebuilt the carb at 5000 miles and reset the timing from 2 Degrees after T.D.C. to 15 degrees before T.D.C. (we power timed it by advancing the spark until it pinged under load then backed off 3 degrees) My first trip was pulling a tent trailer some 800 miles at 55 miles per hour gave 24 miles per gallon.

[tryNto]

RogerDat, They used to be called Service Stations for a reason... Up until the early 70s

[AK Caster]

I love prepaying with my Bank of America credit card. I don't have to go inside for anything and earn a 3% cash rebate on all the gas I purchase up to $1,500 per quarter. Pay the bill when it comes in once a month and zero interest and no annual fees.
Paying for gas with cash is for suckers

[10x]

I love prepaying with my Bank of America credit card. I don't have to go inside for anything and earn a 3% cash rebate on all the gas I purchase up to $1,500 per quarter. Pay the bill when it comes in once a month and zero interest and no annual fees.
Paying for gas with cash is for suckers

And you have a $1500 interest free loan from American Express so long as you pay the bill in full every month.

[jcwit]

And you have a $1500 interest free loan from American Express so long as you pay the bill in full every month.

Not to argue, but

I did the same for decades, whats the problem with doing it that way?

When I retired I now do it the safe way so as not to overspend.

Having an unlimited expense account was great!

[dragon813gt]

Having an unlimited expense account was great!

It most certainly is. I have one and get all the hotel/rental/card points and miles. Averaging close to $10k a month means I won't have to pay for Christmas presents next year. The downside is I'm not home as much.

[10x]

Not to argue, but

I did the same for decades, whats the problem with doing it that way?

When I retired I now do it the safe way so as not to overspend.

Having an unlimited expense account was great!


It most certainly is. I have one and get all the hotel/rental/card points and miles. Averaging close to $10k a month means I won't have to pay for Christmas presents next year. The downside is I'm not home as much.

No problem with running an interest free loan with a credit card company at all. I have done it for over 35 years.

The best was the 6 months interest free cash advance Mastercard offered me.
So long as I paid the minimum balance each month the 45,000 I took as a cash advance was interest free. That got invested in short term G.I.C. at over 5%.
The only catch was that if the Master card balance was not paid off before the 6 month deadline, there was 6 months interest due.
I noticed they never offered me that again....

[xs11jack]

Hey, guys, you are an encyclopedia. I have learned so much. I live 40 miles west of St. Louis in O Fallon, Mo. about 80K people. I can't find any non ethanol gas around here. Normally I buy 10% ethanol 87 octane at Costco. About 10 to 15 cents cheaper than the surrounding stations. I am 73 years old and my hearing is bad enough to need two hearing aid that are the behind the ear type which means my unaided hearing really sucks. Soooo, I would be hard pressed to hear engine knock in the more modern well insulated cars. I guess I will buy 87 octane an soldier on. Thanks for all your really great information.
Ole Jack

[Moonie]

I have a twin turbo charged V6 with 10.5 to 1 compression and direct injection. I can run regular if I want to with no issues, the engine management adjusts. I do however get better power with premium, especially in cold weather, it'll get all 4 of the tires screeching (all wheel drive as well)

[rockrat]

I quit paying with a credit card at the gas pump. Did it on a trip ONCE, and before I got home, someone had charged $13,000 worth of stuff to my card (laptops overnighted to NYC, ect). Took awhile to get it straightened out. Never again

[jcwit]

I quit paying with a credit card at the gas pump. Did it on a trip ONCE, and before I got home, someone had charged $13,000 worth of stuff to my card (laptops overnighted to NYC, ect). Took awhile to get it straightened out. Never again

That's why you have a credit card tied to a checking acct., never can charg more than is in the acct. You control the amount. Impossible to get took that way.

[leadman]

If you use a card tied to your checking account it is probably a debit card. There are fewer protections on these than a true credit card and you could end up footing most of the bill if someone else uses it. My debit card will let me put more on it than what is in the account, just takes the money from savings or a line of credit.

[dragon813gt]

My card was hit because of Target. But it was months after the breach. It was an extreme inconvenience since they shut down my card and I was trying to pay for my lunch. But that's all that it was, an inconvenience.

Card has fraud protection. The charges were immediately reversed and I wasn't responsible for any of it. Had it been a card linked to one of my bank accounts I would have been on the hook for the money until their investigation was complete. In this particular case it was months before I got the notice saying it was fraud and I wasn't responsible.

I much prefer a true credit card over debit/checking cards. There are more protections on a true credit card.

[jcwit]

I realize I have no idea what I talking about. That's why I wet to my bank and setit up the way I did.

Yes it works "like" a debit card, but is in fact a credit card, and can only be used for the amount that is in this "checking" acct. It is a seoerate checking acct., I do not even have any Checks for this acct., it's only function is to be used with the credit card tied to it.

How much more protection do you want?


Maybe this is one advantage to having a small town bank.

[jcwit]

If you use a card tied to your checking account it is probably a debit card. There are fewer protections on these than a true credit card and you could end up footing most of the bill if someone else uses it. My debit card will let me put more on it than what is in the account, just takes the money from savings or a line of credit.

Nope! Not how it works, take my word for it.

[jcwit]

My card was hit because of Target. But it was months after the breach. It was an extreme inconvenience since they shut down my card and I was trying to pay for my lunch. But that's all that it was, an inconvenience.

Card has fraud protection. The charges were immediately reversed and I wasn't responsible for any of it. Had it been a card linked to one of my bank accounts I would have been on the hook for the money until their investigation was complete. In this particular case it was months before I got the notice saying it was fraud and I wasn't responsible.

I much prefer a true credit card over debit/checking cards. There are more protections on a true credit card.

And as I stated in a former post there limited funds in the acct., at most $150.00.

[destrux]

The specs for an engine don't always tell the story on what fuel it needs, but the manufacturer's recommendation does. One example is that Mazda makes a gas engine called the "skyactiv" with a 14:1 compression ratio, naturally aspirated, that they recommend 87 octane fuel for. The secret to that is the engine is carefully (very carefully) designed to avoid preignition, using optimized combustion chamber, exhaust manifold, intake manifold, and direct fuel injection technology (it injects the gas directly into the combustion chamber and not into the intake runner).

The car was designed around using that fuel, and all newer cars are. So when you stray from the factory recommended fuel you always lose something. You generally lose fuel economy, but you also may experience accelerated internal engine fouling. This is a real problem on newer direct injection engines (not to be confused with direct port fuel injection which is old tech). I have customers that attempted to run 87 octane in newer DI cars and found that before 100,000 miles (one was at 37,000!) they had to have the head removed and the intake and head media blasted because the carbon fouling completely obstructed the intake ports to the point the engine wouldn't make enough power to drive anymore. The engine was designed to run a certain fuel grade with a certain timing advance and fuel ratio in order to keep the intake port walls and the intake valves up to a high enough temperature to stop accumulation of carbon. Since there is no fuel coming in through the intake valve on all of the new direct injection engines this is absolutely vital, because there is no fuel detergents to clean the valves like there always has been in previous fuel injected engines. If the computer pulls back the timing and richens the air fuel ratio in reaction to lower octane fuel it lowers the surface temp of the valves, combustion chamber, spark plug tip, and port walls.... and carbon begins to accumulate. It depends on the engine design though, some may not experience it as bad or at all. Early model (circa 2005-2008) Mazda and VW direct injection engines are known to carbon up already without any help (thanks to EPA laws requiring a useless and outdated EGR valve on those model years which sent carbon soot through the intake needlessly) so running lower quality gas will really cause problems, and that engine I had to disassemble and clean at 37,000 miles was a Mazda CX7 direct injection engine being run on 87 octane.

Also, the factory safeguards in the ECU are sometimes only designed to protect against temporary or accidental usage of low octane fuel, and in some cases aren't enough to protect an engine for continual usage and accumulated stress from intermittent engine knock can lead to piston or head gasket failure in the long term. In a few cases the safeguards are only in place to accommodate variations between brands of premium fuel and aren't there to allow for lower octane fuel use at all.

For what it's worth, I'm an ASE master certified tech who's been working general service at my own garage every day for 11 years, I'm not just speculating, this is my own experience with this stuff.

[AK Caster]

Gas station has a fairly thin margin on gas,
How much do they make on a gallon of gas?

[Moonie]

How much do they make on a gallon of gas?

I have a friend that ran c-stores for many years, according to him they make enough off gas to pay for the light bill.

[Mal Paso]

destrux

Great Post, Thanks!

[rockrat]

Gas stations might have a thin margin, but just go up the chain a bit and things change. Look to those that sell to the stations. Many stations are owned by the local distributors (unless that has changed nowadays) and they are just selling to themselves.