Gas....

[HeavyH20]

Do you live/drive at high elevations? octane becomes less and less important the higher above sea level you are... so it may not be the end of the world.

Only for normally aspirated cars. You get a "free" octane point for about every 1000 feet above sea level. Turbo cars make their own atmosphere, so premium is required no matter the altitude.

Great post!!! Thank you.

No problem, even a blind squirrel finds a nut once in a while

 

[Mazdaspeedgirl]

Only for normally aspirated cars. You get a "free" octane point for about every 1000 feet above sea level. Turbo cars make their own atmosphere, so premium is required no matter the altitude.

Good to know...

No problem, even a blind squirrel finds a nut once in a while

he said nut... (sssh)

 

[koala]

Only for normally aspirated cars. You get a "free" octane point for about every 1000 feet above sea level. Turbo cars make their own atmosphere, so premium is required no matter the altitude.



No problem, even a blind squirrel finds a nut once in a while

Ah yes, I suppose turbo vehicles are exempt from this equation.

 

[koala]

If this was the case, the station would be in a lot of trouble as the rating is a MINIMUM rating. I like to think that I'm often getting higher octane than what I pay for, but probably not.

What if you're at a pump that has 87/89/91 all on the same nozzle? Maybe the person before you filled up with 87, and there's 5 litres worth of 87 still in the line? I'm just theorizing here.

I'm just saying that it's probably not exactly 91 octane, and it likely fluctuates.

But is it enough to worry about? No, I doubt it.

 

[Mazdaspeedgirl]

Chevron advertises that they are the only oil company that regulates and tests their gas for octane levels. It's all I use unless there is nothing else available.

Also, might I add that the one vehicle I have owned that I can definitely tell lower grades of gas by performance is my MX-5. If we use anything other than 93 on hot summer days we get pinging. Of course I expect to see a LOT of gunk on the valves when we breakdown the motor that is currently in him. Even detergent synthetic oils changed at 3K intervals and fuel system cleaners did not prevent this from starting at around 80K miles. Hence my use of regular Castrol. Now I have found much more benefit to synthetic gear lubes for the rear diff/tranny. But that is another story...
YAY NEO!!! (first)

 

[koala]

Chevron advertises that they are the only oil company that regulates and tests their gas for octane levels. It's all I use unless there is nothing else available.

Also, might I add that the one vehicle I have owned that I can definitely tell lower grades of gas by performance is my MX-5. If we use anything other than 93 on hot summer days we get pinging. Of course I expect to see a LOT of gunk on the valves when we breakdown the motor that is currently in him. Even detergent synthetic oils changed at 3K intervals and fuel system cleaners did not prevent this from starting at around 80K miles. Hence my use of regular Castrol. Now I have found much more benefit to synthetic gear lubes for the rear diff/tranny. But that is another story...
YAY NEO!!! (first)

You have to wonder if something else is at play if you're experiencing pinging below 93 octane along with needing very frequent oil changes. (theoretically you should be able to go 7,500 miles of hard driving (well, maybe change the filter half way) on a good synthetic.

Have you ever had any UOA tests done?

 

[HeavyH20]

Carbon build up within the cylinder chamber changes over time and changes the effective compression ratio as well as provide hot spots. Then, under pressure, the gas ignites itself without the need for spark much like diesel. Then you get the telltale knock. It also occurs if spark advance is too early, but pretty much all newer cars have knock detection and adjust spark retard accordingly. Higher octane gas has a higher boiling point and is more stable under pressure since there are more long chain molecules.

I just spoil my car with a half tank of 100 octane unleaded once in a while to keep things moving nice

Octane boost is not as effective on Turbo cars since it is simply an oxygenate and dilutes the gas. I usually avoid that except for emergencies when regular is the only choice.

 

[Mazdaspeedgirl]

You have to wonder if something else is at play if you're experiencing pinging below 93 octane along with needing very frequent oil changes. (theoretically you should be able to go 7,500 miles of hard driving (well, maybe change the filter half way) on a good synthetic.

Have you ever had any UOA tests done?

Oh well my timing is advanced a bit on the current motor (sssh). In case you didn't know, the timing on the 99-00 miatas is non VVT.
And it's not NEEDing frequent oil changes (lord knows there's no "change oil" light in the car like some GMs) but just knowledge of what goes on inside the motor when you drive it hard like I do. That and I am old school. dyno juice needs to be changed every 3k.

 

[Mazdaspeedgirl]

You have to wonder if something else is at play if you're experiencing pinging below 93 octane along with needing very frequent oil changes. (theoretically you should be able to go 7,500 miles of hard driving (well, maybe change the filter half way) on a good synthetic.

Have you ever had any UOA tests done?

Oh, and I didn't say it happened everyday; just on very hot days under heavy acceleration (95+ degree days floored up to 7K rpm).

 

[Mazdaspeedgirl]

Carbon build up within the cylinder chamber changes over time and changes the effective compression ratio as well as provide hot spots. Then, under pressure, the gas ignites itself without the need for spark much like diesel. Then you get the telltale knock. It also occurs if spark advance is too early, but pretty much all newer cars have knock detection and adjust spark retard accordingly. Higher octane gas has a higher boiling point and is more stable under pressure since there are more long chain molecules.

Nicely said. You prove my point about why my MX-5 tends to get a bit of knock under certain conditions. No VVT, advanced timing, and known carbon deposits all contribute to it.

It's amazing how some people can perceive octane boosters to make the fuel easier to ignite and "burn more fuel giving more power" when they actually do the opposite. Having almost a decade's experience in auto parts sales, I have heard a lot of people's theories. Not that it's so bad to be unknowledgable, it's just a means to pique one's educational inclination if they can get past the fact that a GIRL told them how it works.