Wrong grade of gas in car

[Anonymous]

My older car requires premium and one day is easier on the ni turnpike abd I asked for premium but the guy started pumping. 87z I immediately told him to stop but he didn’t until about 3 gallons in. He then switched to premium . Aby more 87 and there could have been issues as the average may have dropped below 91 octane . Don’t understand why 89 octane exists. They should offer 87, 91 and 93 though you probably need 89 to make 91

[Anonymous]

Anonymous wrote:My older car requires premium and one day is easier on the ni turnpike abd I asked for premium but the guy started pumping. 87z I immediately told him to stop but he didn’t until about 3 gallons in. He then switched to premium . Aby more 87 and there could have been issues as the average may have dropped below 91 octane . Don’t understand why 89 octane exists. They should offer 87, 91 and 93 though you probably need 89 to make 91

[Anonymous]

Anonymous wrote:

Anonymous wrote:My older car requires premium and one day is easier on the ni turnpike abd I asked for premium but the guy started pumping. 87z I immediately told him to stop but he didn’t until about 3 gallons in. He then switched to premium . Aby more 87 and there could have been issues as the average may have dropped below 91 octane . Don’t understand why 89 octane exists. They should offer 87, 91 and 93 though you probably need 89 to make 91

I read PP's post in Moira Rose's voice. "It's a good thing I was here to stop you from pumping or else there could have been iss-ues! Can't let the average drop below 91!"

[Anonymous]

Anonymous wrote:I drove a semi-luxury car using regular gas for 10 years, and later found that my friend with the same model had been using premium the whole time. I never noticed anything.

I’ve driven BMWs since 1996 and I predominantly use the cheapest gas available and every car has run well until I trade them in with 130-150000 miles

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Is this classified as humble brag?

How so?

Luxury cars typically call for premium fuel.

There are plenty of non-luxury cars that call for 91+ octane fuel.

[Anonymous]

Steps to take?

[Anonymous]

I drive a luxury car and was always under the impression that the different grades were a bit of a scam. If you can get someone to think it's better, they will pay more but really it's all the same. A bit like most organic vegetables.

[Anonymous]

Anonymous wrote:I drive a luxury car and was always under the impression that the different grades were a bit of a scam. If you can get someone to think it's better, they will pay more but really it's all the same. A bit like most organic vegetables.

Which is why you’re not an auto technician or engineer.

Octane grades exist for a reason. The higher the octane rating, the more resistance to spontaneous ignition of the fuel (“knocking”).

Higher performance engines or engines with boosted intake pressure (turbocharged or supercharged engines) or high compression engines produce more power for their relative size, because the higher volume of air being squeezed into each cylinder during the intake stroke and then compressed prior to spark ignition contains more oxygen. So more work is produced by a cylinder with higher compression, and those engines are more powerful (or smaller, while producing the same power as a normally aspirated/lower compression engine.

The problem though is that the fuel air mixture with 87 octane fuel can detonate early in higher compression engines. When this happens, the most noticeable effect is a slight loss of the car’s felt “power” in the seat of the pants.

But the other issue- the one you can’t see happening- is inside the engine, inside the cylinder where the pre-detonation is occurring. When the fuel air mixture detonates early, part of the flame produced during this explosion “squirts” (for lack of a better word) back up into the intake valve openings, which are in the process of closing right at that instant. Part of this high pressure flame imparts high velocity, high temperature gas forces onto the seats of the valves, which aren’t meant to be exposed to this, since normally the valve would be closed by the time the flame front got to them. But since the mixture detonated early, they aren’t. The other thing that’s occurring is that combustion deposits (think “soot”) are being deposited on the back sides of the valves, forming a crust which disrupts smooth flow of the incoming fuel air mixture. These deposits rob performance by causing turbulence and slight restriction of the incoming fuel air mix. Between wearing the valve seats and causing deposits to accumulate, predetonation of fuel will absolutely, positively cause engine damage over time.


I’m sure you’re good at whatever it is you do. But you know nothing about cars or engines.

Stay in your lane and stop giving people harmful advice.

[Anonymous]

Anonymous wrote:I drive a luxury car and was always under the impression that the different grades were a bit of a scam. If you can get someone to think it's better, they will pay more but really it's all the same. A bit like most organic vegetables.

Except car companies don’t sell gasoline, genius. So they have absolutely zero incentive to make you pay more for it. None of it goes into their pockets.

[Anonymous]

Anonymous wrote:

Anonymous wrote:I drive a luxury car and was always under the impression that the different grades were a bit of a scam. If you can get someone to think it's better, they will pay more but really it's all the same. A bit like most organic vegetables.

Which is why you’re not an auto technician or engineer.

Octane grades exist for a reason. The higher the octane rating, the more resistance to spontaneous ignition of the fuel (“knocking”).

Higher performance engines or engines with boosted intake pressure (turbocharged or supercharged engines) or high compression engines produce more power for their relative size, because the higher volume of air being squeezed into each cylinder during the intake stroke and then compressed prior to spark ignition contains more oxygen. So more work is produced by a cylinder with higher compression, and those engines are more powerful (or smaller, while producing the same power as a normally aspirated/lower compression engine.

The problem though is that the fuel air mixture with 87 octane fuel can detonate early in higher compression engines. When this happens, the most noticeable effect is a slight loss of the car’s felt “power” in the seat of the pants.

But the other issue- the one you can’t see happening- is inside the engine, inside the cylinder where the pre-detonation is occurring. When the fuel air mixture detonates early, part of the flame produced during this explosion “squirts” (for lack of a better word) back up into the intake valve openings, which are in the process of closing right at that instant. Part of this high pressure flame imparts high velocity, high temperature gas forces onto the seats of the valves, which aren’t meant to be exposed to this, since normally the valve would be closed by the time the flame front got to them. But since the mixture detonated early, they aren’t. The other thing that’s occurring is that combustion deposits (think “soot”) are being deposited on the back sides of the valves, forming a crust which disrupts smooth flow of the incoming fuel air mixture. These deposits rob performance by causing turbulence and slight restriction of the incoming fuel air mix. Between wearing the valve seats and causing deposits to accumulate, predetonation of fuel will absolutely, positively cause engine damage over time.


I’m sure you’re good at whatever it is you do. But you know nothing about cars or engines.

Stay in your lane and stop giving people harmful advice.

SCIENCE!!!!