Premium Gas = Better Mileage

sack1 · August 28, 2011

On a suggestion from a fellow RVer with another brand of truck, switching to premium gas netted better mpg than the recommended regular. I have an '03 8.1 liter 2500HD and I tow a 13k 5th wheel. I have always used regular gas since that's what the manual says to use and also that the other grades are that much more expensive. Changed the plugs last year and 5 out of the 8 had insulator damage caused by preignition. But as I mentioned, I filled up with premium and my mileage went up about 1 mpg while towing and the same unloaded. This even pays for the difference in cost between the two and because of the plug condition may be easier on the engine.

Anyone else find the same to be true?

Stevens03 · August 28, 2011

In most cases, if your truck isn't programmed for the higher octane fuel, it's not going to have any benefit. But if your seeing better results, continue to use it

seamonster · August 29, 2011

I have been using premium in my vehicles for 25 years. Nobody believes me but they definately

perform better, and get better mileage. Around here some of the premium does not have ethanol

so that alone gains you enough increase in mileage to pay for the cost. Soposedly they have more

additives and cleaning agents but who knows. I use it and I believe it!!!

Mckenzie · August 29, 2011

i filled up with prolly 24-25 gallons of premium gas and made the 170 mile trip home and back up and went the same speed as before and to be honest i noticed no improvement in mpg.

Superperv23 · August 29, 2011

Some cars do return better mpg on higher octane and when you think here in Canada you are looking at a $7 difference in 100 liters between 87 and 91 it can make financial sense. My 5.3 runs a lot smoother with higher octane gas so I buy it, even before it was tuned for it. Most newer cars the ecu can determine what is happening with the octane and adjust for it so there is potential for a difference.

redjewel2ss · August 29, 2011

it all depends on the condition and mileage of your engine. the more miles and wear you put on the engine, the more likely premium will help you stay on the road longer. it has nothing to do with it being "better fuel", the only difference is the time of detonation. when a high mileage vehicle starts knocking/pinging is when you need to change to a higher octane fuel. if it continues, then it needs a tune up.

from http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

Should you ever switch to a higher octane gasoline?
A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

from what you said about the plugs, you were not optimizing your fuel mileage to begin with due to pre-ignition. now that your using premium, and the engine isn't pre-igniting anymore, the engine is back to running as efficient as it can

redjewel2ss · August 29, 2011

In most cases, if your truck isn't programmed for the higher octane fuel, it's not going to have any benefit. But if your seeing better results, continue to use it

this is true for newer vehicles with lower miles... or a properly running engine without preignition problems

redjewel2ss · August 29, 2011

I have been using premium in my vehicles for 25 years. Nobody believes me but they definately
perform better, and get better mileage. Around here some of the premium does not have ethanol

so that alone gains you enough increase in mileage to pay for the cost. Soposedly they have more

additives and cleaning agents but who knows. I use it and I believe it!!!

they don't have more cleaning agents. read this, from link in my previous post:

Will higher octane gasoline clean your engine better?
As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

the top tier fuel companies put the same cleaning agents and concentrations in the regular octane, as they do in the higher octane

dewfpo · August 29, 2011

When I worked for Chevron (until 2000), they put more Techron additive in PUL then they did in MUL and more in MUL than they did in RUL. That was something they were very proud of and an encouragement to buy a higher octane product. That was a fact back then. I can't speak to the amounts they add nowadays.

DEWFPO

Superperv23 · August 29, 2011

When I worked for Chevron (until 2000), they put more Techron additive in PUL then they did in MUL and more in MUL than they did in RUL. That was something they were very proud of and an encouragement to buy a higher octane product. That was a fact back then. I can't speak to the amounts they add nowadays.

DEWFPO

Most stations here in Canada are upfront that their higher grades have more detergents.

wurgs · August 30, 2011

Holiday stations around here post it right on the pumps, more cleaning with the higher grades.

Carder09 · August 30, 2011

I dont know how many times I've had to explain how going grades higher does absolutely nothing gas or performance wise unless your engine calls for 93 octane, your wasting money on something your car/truck is not tuned for. Octane describes how much fuel can be compressed before igniting. So it takes more say 93 octane to ignite than 87. So unless your engine is knocking, which is a bad sign, you probably dont need the higher octane.

Superperv23 · August 30, 2011

I dont know how many times I've had to explain how going grades higher does absolutely nothing gas or performance wise unless your engine calls for 93 octane, your wasting money on something your car/truck is not tuned for. Octane describes how much fuel can be compressed before igniting. So it takes more say 93 octane to ignite than 87. So unless your engine is knocking, which is a bad sign, you probably dont need the higher octane.

Go explain it tho people who design ecm's then

kdixer · August 30, 2011

In most cases, if your truck isn't programmed for the higher octane fuel, it's not going to have any benefit. But if your seeing better results, continue to use it

this is true for newer vehicles with lower miles... or a properly running engine without preignition problems

I dont know how many times I've had to explain how going grades higher does absolutely nothing gas or performance wise unless your engine calls for 93 octane, your wasting money on something your car/truck is not tuned for. Octane describes how much fuel can be compressed before igniting. So it takes more say 93 octane to ignite than 87. So unless your engine is knocking, which is a bad sign, you probably dont need the higher octane.

I Have posted this a couple of times before. When I sent my log files to BB for a custom tune, he noticed alot of KR and asked me what octane I was running. This was a stock 09' 5.3 running 87. He suggested I run atleast 89 because my truck did not seem to like 87. I had noticed before the tuning process that the power curve seemed to be notchy were the ECM was pulling timing to fight spark knock. You could not actually hear any knock. I had tried a diablo predator before the BB tune and noticed that my OEM tune had more spark advance than the Diablo Tune. I posted about it on their forum and everybody acted like I was crazy.

Just as everybody claims the handhelds are no good because a canned tune cannot be ideal for all engines, what do you think the factory tune is? A canned tune plain and simple. GM does not run and monitor each and every engine to see how they perform. Some engines have "personalities" that require different needs. Even though my owners manual states I can run 87, that does not mean I cannot possibly benefit from running 89 or higher.

It does not take more 93 octane fuel to ignite compared to 87. Higher octane fuel burns slower than lower octane fuel. The idea behind running high octane is to light the mixture sooner creating more pressure by the longer burn cycle to push down on the piston. Higher octane prevents spark knock because it is more stable under pressure than lower octane fuel. Ideally you want a certain percent of the burn cycle to be complete by the time the piston reaches TDC. That % is used to build pressure and the remainder is to launch the piston downward during the power stroke. Lets say that percent is 70 just as an example. If an engine is running 87 and 70% of the burn is complete by TDC then great. However if a particular engine running 87 completes 80% of the burn cycle before TDC, then that engine will benefit from a higher octane fuel. It will build good pressure but the burn cycle will not continue during the power stroke so it will not create as much power as possible. You can either retune ignition timing to retard the ignition process which will result in less power. Or you can run slightly higher octane fuel which will result in a longer burn cycle and more power.That same engine on higher octan, say 89, will complete 70% of the burn cycle leaving the ideal 30% to burn during the power stroke. Again these numbers are not "real" and are intended for explanation purposes only.

Carder09 · August 30, 2011

In most cases, if your truck isn't programmed for the higher octane fuel, it's not going to have any benefit. But if your seeing better results, continue to use it

this is true for newer vehicles with lower miles... or a properly running engine without preignition problems

I dont know how many times I've had to explain how going grades higher does absolutely nothing gas or performance wise unless your engine calls for 93 octane, your wasting money on something your car/truck is not tuned for. Octane describes how much fuel can be compressed before igniting. So it takes more say 93 octane to ignite than 87. So unless your engine is knocking, which is a bad sign, you probably dont need the higher octane.

I Have posted this a couple of times before. When I sent my log files to BB for a custom tune, he noticed alot of KR and asked me what octane I was running. This was a stock 09' 5.3 running 87. He suggested I run atleast 89 because my truck did not seem to like 87. I had noticed before the tuning process that the power curve seemed to be notchy were the ECM was pulling timing to fight spark knock. You could not actually hear any knock. I had tried a diablo predator before the BB tune and noticed that my OEM tune had more spark advance than the Diablo Tune. I posted about it on their forum and everybody acted like I was crazy.

Just as everybody claims the handhelds are no good because a canned tune cannot be ideal for all engines, what do you think the factory tune is? A canned tune plain and simple. GM does not run and monitor each and every engine to see how they perform. Some engines have "personalities" that require different needs. Even though my owners manual states I can run 87, that does not mean I cannot possibly benefit from running 89 or higher.

It does not take more 93 octane fuel to ignite compared to 87. Higher octane fuel burns slower than lower octane fuel. The idea behind running high octane is to light the mixture sooner creating more pressure by the longer burn cycle to push down on the piston. Higher octane prevents spark knock because it is more stable under pressure than lower octane fuel. Ideally you want a certain percent of the burn cycle to be complete by the time the piston reaches TDC. That % is used to build pressure and the remainder is to launch the piston downward during the power stroke. Lets say that percent is 70 just as an example. If an engine is running 87 and 70% of the burn is complete by TDC then great. However if a particular engine running 87 completes 80% of the burn cycle before TDC, then that engine will benefit from a higher octane fuel. It will build good pressure but the burn cycle will not continue during the power stroke so it will not create as much power as possible. You can either retune ignition timing to retard the ignition process which will result in less power. Or you can run slightly higher octane fuel which will result in a longer burn cycle and more power.That same engine on higher octan, say 89, will complete 70% of the burn cycle leaving the ideal 30% to burn during the power stroke. Again these numbers are not "real" and are intended for explanation purposes only.

I guess I didnt phrase it correctly when I wrote about it takes more93 to ignite than 87, what I meant is what I had wrote beforehand about how much (93) can compress before igniting preventing pre-ignition compared to 87 that has the potential for creating pings/knocks. But Usually now-a-days cars come standard with knock sensors, that really help prevent pre ignition by "retarding" the spark so that there isnt any unwanted pings/knocks.(what you stated above) Also you have to factor the quality of the gas stations gas. I know my truck doesnt like watered down gas that wal-mart, sams club, kroger etc do and possibly have so I will usually go to a Shell, or exxon and even a quik trip. But I will continue to run 93 octane in my truck since I have it tuned to do so.