Longevity of A Vehicle...

[madrussian]

I was filling up my gf's Jetta tonight, and I got to wondering.

Does the octane used add or decrease the longevity of a motor in a car? For example, she's a 2.5L so if I put in 93 as opposed to 87 am I going to increase longevity or just pay more for some extra oomph essentially?

I suppose we can throw the oil debate in here too, how often is too much or too little. She goes the 10k mark, I go by the 5k on mine.

[thegolfer18]

You neither increase the longevity or add an extra oomph by filling up with higher octane gas than your engine recommends.

[bherman13]

These questions usually start a storm of fans from both sides. I imagine longevity is not affected by grade of gas, just quality, which doesn't usually matter because "all gas is the same so the quality is the same". Oil shouldn't go past when it starts to break down, obviously. If you want to know how close to the end off your oil's life you went, send of a sample for analysis.

[Live-Wire]

The only advantage to using the higher octane fuel in a car that doesn't recommend or require it is the added detergents which keep the injectors cleaner. Using regular seems to require doing a top end cleaning every couple years, while vehicles running premium don't seem to need it.

The cost of running the more expensive fuel would outweigh the cost of Seafoam every year tho...

More octane actually has slightly less power per unit measure... It only improves performance in a high compression motor which would knock if running at peak tune on regular.

[B3sat16v]

You neither se the longevity or add an extra oomph by filling up with higher octane gas than your engine recommends.

Actually you do add more power, not much, but power goes up with higher octane. Why do you think that people would use 100 Octane when they race?

There are quite a few examples out there where higher or lower octanes would increase or decrease power respectively.

Longevity, as long as you use some good fuels, should be OK.

[B3sat16v]

More octane actually has slightly less power per unit measure... It only improves performance in a high compression motor which would knock if running at peak tune on regular.

It is not power, is energy, they are related, but not the same thing. And when a car is tuned to run on 87, like the Camry, but because of advanced engine management, it will have power increase with 91-93.

The engine was actually designed to run 91-93, but due to the economy and the advanced Engine Management Controls Systems, it can run 87 just fine without spark knocking. Hell my GLI with a Stage II 93 tune can run 87 and not spark knock.

[Lifelong Obsession]

The gas grade best for a vehicle is what's described in the owner's manual and behind the gas door. Nothing more, nothing less.

If it says "87 octane"...use 87 octane.
If it says "premium fuel only"...use 91 or higher.
If it says "premium fuel recommended"...check forums to see what gives the best power and mileage.

Of course, there are certain folks that just don't get it...like my uncle who will lease a BMW for $800/month but thinks the required premium fuel is "too expensive", since "I'm not bringing it to a racetrack."

Oil changes - once again, follow the manual, unless the car has some known problem/TSB with the recommended intervals.

Of course, if you have an engine like a Chrysler 2.7, you're S.O.L no matter how often you change the oil and what type it is.

[thegolfer18]

Actually you do add more power, not much, but power goes up with higher octane. Why do you think that people would use 100 Octane when they race?

There are quite a few examples out there where higher or lower octanes would increase or decrease power respectively.

Longevity, as long as you use some good fuels, should be OK.

Which is why I said higher than your engine recommends

[B3sat16v]

Which is why I said higher than your engine recommends

Camry recommends 87 on the new V6. With 87 it develops 268HP, with 91 or 93 anywhere from 272 to 275 HP. The older 300 M also recommended 87, but the manual would tell you that with Premium higher HP would be achieved. Again, not much, but there is a gain.

[SSLByron]

Camry recommends 87 on the new V6. With 87 it develops 268HP, with 91 or 93 anywhere from 272 to 275 HP. The older 300 M also recommended 87, but the manual would tell you that with Premium higher HP would be achieved. Again, not much, but there is a gain.

There's a gain if the car is programmed to take advantage of it. Not all cars are/do.

And are you sure they "recommend" 87 on the Camry V6? Many cars have a "required" octane and a "recommended" octane, so you'll know right off the bat that the ECU is adaptive.

[zhenya00]

Actually you do add more power, not much, but power goes up with higher octane. Why do you think that people would use 100 Octane when they race?

Not a true statement unless qualified by 'in certain engines.' Using a higher octane than your motor was designed for is a waste of money, and in some cases, can even cause a drop in performance or economy.

There is no difference in the amount of 'energy' or 'power' stored in different grades of gas. Octane is simply a measurement of how resistant the fuel is to burn. Higher octane may be compressed more than lower octane without pre-igniting; allowing for a design with a higher compression ratio. More compression means a bigger bang meaning more power. If the motor is built with a compression ratio suitable for 87, running 93 is just a waste of money and efficiency.

[SSLByron]

Not a true statement unless qualified by 'in certain engines.' Using a higher octane than your motor was designed for is a waste of money, and in some cases, can even cause a drop in performance or economy.

There is no difference in the amount of 'energy' or 'power' stored in different grades of gas. Octane is simply a measurement of how resistant the fuel is to burn. Higher octane may be compressed more than lower octane without pre-igniting; allowing for a design with a higher compression ratio. More compression means a bigger bang meaning more power. If the motor is built with a compression ratio suitable for 87, running 93 is just a waste of money and efficiency.

Bingo. So to answer this:

Why do you think that people would use 100 Octane when they race?

Race gas is higher-octane because race engines tend to have higher compression ratios and more aggressive timing.

Some owners, especially those running more aggressive-than-stock ECU maps, will use a higher octane fuel when they track their cars because they don't want to risk detonation due to the heat generated by extended high-RPM running. They're not looking for power. They're looking for a safety cushion.

[mac dre]

Depends on the motor, while the VW 2.5 motor runs on 87. If you put 91 in it consistently, the ECU will adapt and provide a minor HP increase 5-10HP I think was what I last saw.

[Grey Mouser]

Depends on the motor, while the VW 2.5 motor runs on 87. If you put 91 in it consistently, the ECU will adapt and provide a minor HP increase 5-10HP I think was what I last saw.

No, just... no.

[B3sat16v]

Not a true statement unless qualified by 'in certain engines.' Using a higher octane than your motor was designed for is a waste of money, and in some cases, can even cause a drop in performance or economy.

There is no difference in the amount of 'energy' or 'power' stored in different grades of gas. Octane is simply a measurement of how resistant the fuel is to burn. Higher octane may be compressed more than lower octane without pre-igniting; allowing for a design with a higher compression ratio. More compression means a bigger bang meaning more power. If the motor is built with a compression ratio suitable for 87, running 93 is just a waste of money and efficiency.

And you are wrong. The lower the octane the higher the energy content; however, since you cannot run higher compression, and cannot increase the thermodynamic efficiency, it does not make as much power.

[B3sat16v]

Race gas is higher-octane because race engines tend to have higher compression ratios and more aggressive timing.

Some owners, especially those running more aggressive-than-stock ECU maps, will use a higher octane fuel when they track their cars because they don't want to risk detonation due to the heat generated by extended high-RPM running. They're not looking for power. They're looking for a safety cushion.

Have any of you have studied engines, like graduate level classes and applied it and then tested them?

[TM87]

You are basically wasting moneyand in some cases can decrease mpgs. Your ecu,timing and air to fuel ratio is preprogrammed for 87. That's the best fuel grade to use.
I have ecu that can switch between 91 and 93 depending on use.

[Aonarch]

[SGLoki]

Actually you do add more power, not much, but power goes up with higher octane. Why do you think that people would use 100 Octane when they race?

There are quite a few examples out there where higher or lower octanes would increase or decrease power respectively.

Longevity, as long as you use some good fuels, should be OK.

Higher octane gas detonates less readily, it is not a huge benefit (if any) in stock vehicles. The reason a vehicle needs higher octane ratings is to reduce predetonation that can result from higher compression ratios.

If you increase the compression ratio of an engine it stands to reason you should also increase the octane IF you suffer pinging or pre-det. IF not, it's just a waste of money.


As someone else said, gasoline quality has more to do with longevity. Save the extra $ to put on routine maintenance, baby the car, and don't drive it over 55mph if you want longevity.

[mac dre]

No, just... no.

http://www.europeancarweb.com/tech/p...n/viewall.html

see ya.

[B3sat16v]

Higher octane gas detonates less readily, it is not a huge benefit (if any) in stock vehicles. The reason a vehicle needs higher octane ratings is to reduce predetonation that can result from higher compression ratios.

If you increase the compression ratio of an engine it stands to reason you should also increase the octane IF you suffer pinging or pre-det. IF not, it's just a waste of money.


As someone else said, gasoline quality has more to do with longevity. Save the extra $ to put on routine maintenance, baby the car, and don't drive it over 55mph if you want longevity.

All of you do a bunch of typing without actual back up. Have any of you done a graduate level engine studies?

[thegolfer18]

All of you do a bunch of typing without actual back up. Have any of you done a graduate level engine studies?

Enlighten us plebeians who have not done any graduate level engine studies please

[Grey Mouser]

http://www.europeancarweb.com/tech/p...n/viewall.html

see ya.

This is an exception, not the rule. Most cars don't do better on fuel they aren't designed for.

[mac dre]

Right, which is exactly why I said "Depends on the motor"

...

[dirtygmc]

All of you do a bunch of typing without actual back up. Have any of you done a graduate level engine studies?

Where are your back up references?

Yeah, the lower octanes do have higher BTU/energy ratings, but a 10k BTU variance is negligible for people outside of a dyno shop. The primary reason for higher octanes is to run higher compression, which do make a considerable difference. ECU allowances aside, it does nothing noticeable for real life, seat of the pants power or engine longevity.

[Subie J]

I put c16 in my prius once, I pulled on liter bikes all day long.

[B3sat16v]

Enlighten us plebeians who have not done any graduate level engine studies please

Go take a course yourself. I am not here to quote or reference my books.

Most modern engine can run multiple octanes. These days they will run 87 and the ECU will adapt to 93 and add a bit of power by changing timing etc etc etc.. This is not 80s, or the 90s even.

[Grey Mouser]

I put c16 in my prius once, I pulled on liter bikes all day long.

But did you chirp third?

[leaftye]

You neither increase the longevity or add an extra oomph by filling up with higher octane gas than your engine recommends.

This.

It does increase the longevity of your joints though. A lighter wallet does that.

[leaftye]

Bingo. So to answer this:



Race gas is higher-octane because race engines tend to have higher compression ratios and more aggressive timing.

Some owners, especially those running more aggressive-than-stock ECU maps, will use a higher octane fuel when they track their cars because they don't want to risk detonation due to the heat generated by extended high-RPM running. They're not looking for power. They're looking for a safety cushion.

That might be the case, but I'll opt for higher octane to offset the higher temperatures seen at the track that make predetonation more likely. Very few factory equipped cars can handle the very high temperatures of track duty, so little things like this help.

[JLJetta]

If one runs too low of an octane, and your engine has significant predetonation, your longevity may be hindered.

Outside of that, the answer is 'it depends'. Along with a few engine "tweaks", my old GTI went from ~130wbhp at 91 to over 325wbhp on MS100.


Speaking of which, what "graduate level engine studies" would be best to understand cavitation in the fuel flow when operating at around 6500 psia?

[GoFaster]

Actually you do add more power, not much, but power goes up with higher octane. Why do you think that people would use 100 Octane when they race?

... Only appropriate if the engine is built to use that fuel (high compression, etc) and in that case, the engine cannot run (for very long) on lower octane fuel.

People not involved in racing may not grasp that there is no such thing as "race gas". There are many, MANY customized fuels available for various racing applications but there is no single thing called "race gas".

Some racing fuels such as VP MR12 are only 87 octane. It's meant for getting more power out of production or nearly-stock engines with near-stock compression ratio.

On the other hand, VP C12 is 108 octane and is meant for compression ratios up to 15:1 ...

[Spinnaker]

~130wbhp at 91 to over 325wbhp :

Wheel Brake Horsepower?

[B3sat16v]

... Only appropriate if the engine is built to use that fuel (high compression, etc) and in that case, the engine cannot run (for very long) on lower octane fuel.

People not involved in racing may not grasp that there is no such thing as "race gas". There are many, MANY customized fuels available for various racing applications but there is no single thing called "race gas".

Some racing fuels such as VP MR12 are only 87 octane. It's meant for getting more power out of production or nearly-stock engines with near-stock compression ratio.

On the other hand, VP C12 is 108 octane and is meant for compression ratios up to 15:1 ...

What I realize is that I should have been more specific. Modern engines with high CR are capable of running 87 and 91-93 due to their advanced engine management systems. The issue here is that with the gas prices as high as they are companies are now saying 87 or higher in their manuals. My Lexus says 87 can be used in the car, but for maximum performance 91 or higher is recommended. I have already stated all of this. I am not sure why this does not pass some of you knuckle heads. There are many cars out there with high CR, that will benefit from higher octane. And as for the "racing fuel" a car with a tune can run a more aggressive timing providing slight increase in performance. Hell with with just a modern ECU it will do this.

[Jamez]

Here is one possible scenario where using premium could prolong the life of your car : Older cars not meant to run ethanol could actually benefit from running on premium that has less or no ethanol in it.