Premium Vs. Regular Test

[PilotguyPA28]

I'll report back what my mileage is. I know what it normally is so I'll see if there's a large variation. I don't mind using Premium but am just curious.

********************************************************************************

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Ok, here's the results in an '03 430LS driven in Alabama. I ran nearly 3/4 tank of regular (non-ethenol) in it the past 12 days. I filled it up when almost empty to get the best result. I drove around town normally and even floored it a few times. There is definately a power difference. How much I can't say. There is a slight lag in acceleration which is not normal.

With premium I usually get no better than 17 in town and normally 16.5. This 3/4 tank gave me 16 exactly. So the difference in 16 and 16.5 is a 3.125% decrease in mileage. Premium is $0.25 per gallon more here and I paid $3.90 for regular. That is a difference of 6.41%.

So, from my experiment you would see a reduction of approximately 3.125% in fuel mileage but you would save 6.41% on the cost of the fuel. You have to factor the decrease in power as well as any "unknown" there may be. I calculated that will cost me about $150 per year for Premium which I am willing to pay.

I have not tested this on the highway. As soon as I get a good trip where I can check the difference on the Interstate I will post it.

Hope this helps!

Pilotguy

[jcrome04]

There is A LOT of info on this topic.

What's your usual mileage on a tank, and average mpg?

I'm putting MY money on lower mpg's. Let us know about a power difference if you notice any.

[PilotguyPA28]

A power difference would be negligable the way I drive. I usually get between 16 and 17 in town. I'm doing about 250 highway miles Saturday so I can just watch on a level stretch and see what I am getting at 75. I'll need a weeks worth of in-town driving to actually get a good average on in-town driving.

[SRK]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings and higher rpm, as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required. Pilotguy, my prediction is similar fuel mileage.

[wrpsuite]

I ran some tests last year and here is what happened.

The first few tanks there was no real noticeable difference. I was a bit cautious and sometimes topped off with Ultra but for the most part no problem. Then mileage started to drop off about 2-3 mpg and the pinging started if I used off brand gas. I went ahead and ran it all the way down and filled with Sunoco 94 octane and it was like driving a new car. The throttle response was noticeable and I haven't used anything less than mid grade since. I really don't think the savings are worth it but it just my 2 cents (literally).. hope this helps

[wwest]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings

and higher rpm,

Not really. The most danger from octane being too low occurs with relatively high engine loading (HARD pulling), low RPM and WOT throttle. The cylinder is getting a FULL charge, the low octane "flame front" advances too fast for the piston to move away/downward (due to "downstream" LOAD) and you get a serious, detrimental, level of knock/ping. Some call it lugging the engine.

As the RPM climbs higher and higher the HP/torque rises also and now the piston moves more rapidly, in comparison to the flame front.

as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

"higher octane is not required...

Well, yes, and NO.

To conserve fuel, modern day engine/transaxle ECU control systems make full use of the wide range of the new 6 (9??***) speed gearboxes. CVT "emulation" mode, if you will. The ECU tries its damndest to always run the engine right in the CUSP between knock/ping due to lugging and just barely generating enough HP/torque to move the vehicle along at the current speed and road conditions/circumstance.

The ECU uses the crankshaft position sensor and the more sensitive non-resonant knock/ping sensor to determine just exactly where/when the A/F mixture ignites in relation to the crankshift position. Obviously if it ignites prior to ignition firing something is quite seriously wrong. But mostly the ECU wants to know if the flame-front of the fuel, once ignited normally, moves too fast for the rate at which the piston can move downward/away due to downstream loading, resulting in even a slight level of knock/ping, certainly much lower that can be heard by the human ear.

Should this happen there are to paths, avenues, the ECU can use for correction. First, it will enrich the mixture, just slightly, to alleviate the low level of knock/ping. If that action doesn't work then it will command a transaxle downshift in order to raise the engine RPM into a range wherein the HP/torque it produces is more appropriate to the current downstream drive train load, loading.

Pilotguy, my prediction is similar fuel mileage.

Many of you have undoubtedly noticed just how "busy" these new transaxles have become. Oftentimes, seemingly, virtually continuous down/upshifting as we drive along on to us, relatively smooth and level roadbeds. That continuous up/downshifting is a direct result of the modern technological improvements available to the automotive manufacturers of today. These newer 250-300HP V6 engines can now be safely operated at extraordinarily low RPMs, RPMs that in the past, "near" past, would have put the engine's service life at risk to inadvertent (undetectable) knock/ping from, due to, lugging.

CVTs, coming soon to a car near you, will help.

*** There are now, often, due to the wider useful RPM range of these new (over-powered??) V6 engines, two actual O/D "hard" gear ratios available. Plus the O/D lockup clutch might be optionally used in the top 3, or even 4 "hard" gear ratios, resulting in a 9 or 10 speed gearbox. Use of the O/D lockup clutch now only changes the drive train's final drive ratio, but also results in sigificantly increasing FE due to the removal of the highly lossy torque converter being out of the loop.

[jrbtn]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings

and higher rpm,

Not really. The most danger from octane being too low occurs with relatively high engine loading (HARD pulling), low RPM and WOT throttle. The cylinder is getting a FULL charge, the low octane "flame front" advances too fast for the piston to move away/downward (due to "downstream" LOAD) and you get a serious, detrimental, level of knock/ping. Some call it lugging the engine.

As the RPM climbs higher and higher the HP/torque rises also and now the piston moves more rapidly, in comparison to the flame front.

as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

"higher octane is not required...

Well, yes, and NO.

To conserve fuel, modern day engine/transaxle ECU control systems make full use of the wide range of the new 6 (9??***) speed gearboxes. CVT "emulation" mode, if you will. The ECU tries its damndest to always run the engine right in the CUSP between knock/ping due to lugging and just barely generating enough HP/torque to move the vehicle along at the current speed and road conditions/circumstance.

The ECU uses the crankshaft position sensor and the more sensitive non-resonant knock/ping sensor to determine just exactly where/when the A/F mixture ignites in relation to the crankshift position. Obviously if it ignites prior to ignition firing something is quite seriously wrong. But mostly the ECU wants to know if the flame-front of the fuel, once ignited normally, moves too fast for the rate at which the piston can move downward/away due to downstream loading, resulting in even a slight level of knock/ping, certainly much lower that can be heard by the human ear.

Should this happen there are to paths, avenues, the ECU can use for correction. First, it will enrich the mixture, just slightly, to alleviate the low level of knock/ping. If that action doesn't work then it will command a transaxle downshift in order to raise the engine RPM into a range wherein the HP/torque it produces is more appropriate to the current downstream drive train load, loading.

Pilotguy, my prediction is similar fuel mileage.

Many of you have undoubtedly noticed just how "busy" these new transaxles have become. Oftentimes, seemingly, virtually continuous down/upshifting as we drive along on to us, relatively smooth and level roadbeds. That continuous up/downshifting is a direct result of the modern technological improvements available to the automotive manufacturers of today. These newer 250-300HP V6 engines can now be safely operated at extraordinarily low RPMs, RPMs that in the past, "near" past, would have put the engine's service life at risk to inadvertent (undetectable) knock/ping from, due to, lugging.

CVTs, coming soon to a car near you, will help.

*** There are now, often, due to the wider useful RPM range of these new (over-powered??) V6 engines, two actual O/D "hard" gear ratios available. Plus the O/D lockup clutch might be optionally used in the top 3, or even 4 "hard" gear ratios, resulting in a 9 or 10 speed gearbox. Use of the O/D lockup clutch now only changes the drive train's final drive ratio, but also results in sigificantly increasing FE due to the removal of the highly lossy torque converter being out of the loop.

Good explanation from someone who knows modern engine management systems. Most of us have little appreciation for the depth of technology used to get the most power and MPG from our engines.

[SRK]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings

and higher rpm,

Not really. The most danger from octane being too low occurs with relatively high engine loading (HARD pulling), low RPM and WOT throttle. The cylinder is getting a FULL charge, the low octane "flame front" advances too fast for the piston to move away/downward (due to "downstream" LOAD) and you get a serious, detrimental, level of knock/ping. Some call it lugging the engine.

As the RPM climbs higher and higher the HP/torque rises also and now the piston moves more rapidly, in comparison to the flame front.

as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

"higher octane is not required...

Well, yes, and NO.

To conserve fuel, modern day engine/transaxle ECU control systems make full use of the wide range of the new 6 (9??***) speed gearboxes. CVT "emulation" mode, if you will. The ECU tries its damndest to always run the engine right in the CUSP between knock/ping due to lugging and just barely generating enough HP/torque to move the vehicle along at the current speed and road conditions/circumstance.

The ECU uses the crankshaft position sensor and the more sensitive non-resonant knock/ping sensor to determine just exactly where/when the A/F mixture ignites in relation to the crankshift position. Obviously if it ignites prior to ignition firing something is quite seriously wrong. But mostly the ECU wants to know if the flame-front of the fuel, once ignited normally, moves too fast for the rate at which the piston can move downward/away due to downstream loading, resulting in even a slight level of knock/ping, certainly much lower that can be heard by the human ear.

Should this happen there are to paths, avenues, the ECU can use for correction. First, it will enrich the mixture, just slightly, to alleviate the low level of knock/ping. If that action doesn't work then it will command a transaxle downshift in order to raise the engine RPM into a range wherein the HP/torque it produces is more appropriate to the current downstream drive train load, loading.

Pilotguy, my prediction is similar fuel mileage.

Many of you have undoubtedly noticed just how "busy" these new transaxles have become. Oftentimes, seemingly, virtually continuous down/upshifting as we drive along on to us, relatively smooth and level roadbeds. That continuous up/downshifting is a direct result of the modern technological improvements available to the automotive manufacturers of today. These newer 250-300HP V6 engines can now be safely operated at extraordinarily low RPMs, RPMs that in the past, "near" past, would have put the engine's service life at risk to inadvertent (undetectable) knock/ping from, due to, lugging.

CVTs, coming soon to a car near you, will help.

*** There are now, often, due to the wider useful RPM range of these new (over-powered??) V6 engines, two actual O/D "hard" gear ratios available. Plus the O/D lockup clutch might be optionally used in the top 3, or even 4 "hard" gear ratios, resulting in a 9 or 10 speed gearbox. Use of the O/D lockup clutch now only changes the drive train's final drive ratio, but also results in sigificantly increasing FE due to the removal of the highly lossy torque converter being out of the loop.

What you are speaking of is "spark knock" caused by, as you explain wordily, ignition timing. I am speaking of knock caused by BMEP, which is the kind of detonation that destroys engines, and is caused by combustion chamber pressures exceeding the octane value and hence the knock resistance, of the fuel.

Your career in rocket science has failed you.

Pilotguy undestands BMEP as he is a pilot, like me.

[wwest]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings

and higher rpm,

Not really. The most danger from octane being too low occurs with relatively high engine loading (HARD pulling), low RPM and WOT throttle. The cylinder is getting a FULL charge, the low octane "flame front" advances too fast for the piston to move away/downward (due to "downstream" LOAD) and you get a serious, detrimental, level of knock/ping. Some call it lugging the engine.

As the RPM climbs higher and higher the HP/torque rises also and now the piston moves more rapidly, in comparison to the flame front.

as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

"higher octane is not required...

Well, yes, and NO.

To conserve fuel, modern day engine/transaxle ECU control systems make full use of the wide range of the new 6 (9??***) speed gearboxes. CVT "emulation" mode, if you will. The ECU tries its damndest to always run the engine right in the CUSP between knock/ping due to lugging and just barely generating enough HP/torque to move the vehicle along at the current speed and road conditions/circumstance.

The ECU uses the crankshaft position sensor and the more sensitive non-resonant knock/ping sensor to determine just exactly where/when the A/F mixture ignites in relation to the crankshift position. Obviously if it ignites prior to ignition firing something is quite seriously wrong. But mostly the ECU wants to know if the flame-front of the fuel, once ignited normally, moves too fast for the rate at which the piston can move downward/away due to downstream loading, resulting in even a slight level of knock/ping, certainly much lower that can be heard by the human ear.

Should this happen there are to paths, avenues, the ECU can use for correction. First, it will enrich the mixture, just slightly, to alleviate the low level of knock/ping. If that action doesn't work then it will command a transaxle downshift in order to raise the engine RPM into a range wherein the HP/torque it produces is more appropriate to the current downstream drive train load, loading.

Pilotguy, my prediction is similar fuel mileage.

Many of you have undoubtedly noticed just how "busy" these new transaxles have become. Oftentimes, seemingly, virtually continuous down/upshifting as we drive along on to us, relatively smooth and level roadbeds. That continuous up/downshifting is a direct result of the modern technological improvements available to the automotive manufacturers of today. These newer 250-300HP V6 engines can now be safely operated at extraordinarily low RPMs, RPMs that in the past, "near" past, would have put the engine's service life at risk to inadvertent (undetectable) knock/ping from, due to, lugging.

CVTs, coming soon to a car near you, will help.

*** There are now, often, due to the wider useful RPM range of these new (over-powered??) V6 engines, two actual O/D "hard" gear ratios available. Plus the O/D lockup clutch might be optionally used in the top 3, or even 4 "hard" gear ratios, resulting in a 9 or 10 speed gearbox. Use of the O/D lockup clutch now only changes the drive train's final drive ratio, but also results in sigificantly increasing FE due to the removal of the highly lossy torque converter being out of the loop.

What you are speaking of is "spark knock" caused by, as you explain wordily, ignition timing. I am speaking of knock caused by BMEP, which is the kind of detonation that destroys engines, and is caused by combustion chamber pressures exceeding the octane value and hence the knock resistance, of the fuel.

Your career in rocket science has failed you.

Pilotguy undestands BMEP as he is a pilot, like me.

And here I though I have covered all three instances, causative factors for engine knock/ping.

1. Ignition too early..

2. Pre-ignition before spark due to low octane, A/F mixture too lean, overheated engine block, or "glowing" carbon deposits.

3. Engine lugging.. flame-front travel rate exceeding downward "speed" of piston. First noticeable at WOT and LOW RPM and if allowed to continue, exist all the way into higher RPMs, will be highly destructive to the engine. Recipricating engines have a HP/Torque curve/graph that indicate a rise in HP/Torque with RPM so "lugging" is much more probable, prevalent, at lower engine RPMs.

Knock/ping due to lugging the engine using a stick shift can happen with ANY octane but more likely with octane too low for compression ratio.

I guess I must have missed something in pilot school/training but then insofar as I know our C210 nor my T210 ever "suffered" due to my lack of knowledge.

Since detonation in an airplane engine cannot be so readily heard it is best to always lean slightly to the RICH side using the EGT gage. This is probably the extent of my knowledge unique to airplane engine operation on this matter.

[Lexusfreak]

There is A LOT of info on this topic.

What's your usual mileage on a tank, and average mpg?

I'm putting MY money on lower mpg's. Let us know about a power difference if you notice any.

I'll put my money on both being very similar......I tried this when I first got my 2005 ES.....did not notice a single difference between the regular & higher octane grades.

Now if only I had the money back I spent over the years on premium fuel... :whistles:

[wwest]

I've said this many times before, and I'll say it again.

The advantage of higher octane is only realized at large throttle openings and higher rpm, as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure.

Oh, now I see the fallacy in your statement that I initially overlooked. Thanks for calling it to my attention...

In order to get to point "B" you MUST start at point "A".

It is not possible to get to higher RPMs and WOT without first being at a LOW RPM and WOT. Assuming a relatively constant load on the engine, knock/ping due to octane being too low would be noticeable at low RPM, where the engine is not producing anything close to maximum rated HP. In reality if you encounter knock/ping at low RPM and WOT it is highly likely to abate as RPM, and HP, climbs.

Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

Pilotguy, my prediction is similar fuel mileage.

Your prediction would have been valid maybe 5-10 years ago before the technology became available and began to be used to keep the engine operating right on the cusp between lugging and producing just barely enough HP/torque for overall "conditions". There can be little or no doubt that in today's high technology world low octane fuel in a high compression engine will result in lower FE than with premium.

Sorry, you simply cannot compare the obsolete "technology" that today remains in current use in aircraft engines with the much more current, up-to-date, technology today used in our modern automotive engines.

[wwest]

I've said this many times before, and I'll say it again. The advantage of higher octane is only realized at large throttle openings

and higher rpm,

Not really. The most danger from octane being too low occurs with relatively high engine loading (HARD pulling), low RPM and WOT throttle. The cylinder is getting a FULL charge, the low octane "flame front" advances too fast for the piston to move away/downward (due to "downstream" LOAD) and you get a serious, detrimental, level of knock/ping. Some call it lugging the engine.

As the RPM climbs higher and higher the HP/torque rises also and now the piston moves more rapidly, in comparison to the flame front.

as detonation -at least the dangerous kind - is only a concern under conditions of raised cylinder pressure. Unlike a diesel, gasoline engines throttle air and fuel, and at small throttle openings there is not enough pressure to cause detonation. So in gentle driving, which I think describes the driving habits of many, the higher octane is not required.

"higher octane is not required...

Well, yes, and NO.

To conserve fuel, modern day engine/transaxle ECU control systems make full use of the wide range of the new 6 (9??***) speed gearboxes. CVT "emulation" mode, if you will. The ECU tries its damndest to always run the engine right in the CUSP between knock/ping due to lugging and just barely generating enough HP/torque to move the vehicle along at the current speed and road conditions/circumstance.

The ECU uses the crankshaft position sensor and the more sensitive non-resonant knock/ping sensor to determine just exactly where/when the A/F mixture ignites in relation to the crankshift position. Obviously if it ignites prior to ignition firing something is quite seriously wrong. But mostly the ECU wants to know if the flame-front of the fuel, once ignited normally, moves too fast for the rate at which the piston can move downward/away due to downstream loading, resulting in even a slight level of knock/ping, certainly much lower that can be heard by the human ear.

Should this happen there are to paths, avenues, the ECU can use for correction. First, it will enrich the mixture, just slightly, to alleviate the low level of knock/ping. If that action doesn't work then it will command a transaxle downshift in order to raise the engine RPM into a range wherein the HP/torque it produces is more appropriate to the current downstream drive train load, loading.

Pilotguy, my prediction is similar fuel mileage.

Many of you have undoubtedly noticed just how "busy" these new transaxles have become. Oftentimes, seemingly, virtually continuous down/upshifting as we drive along on to us, relatively smooth and level roadbeds. That continuous up/downshifting is a direct result of the modern technological improvements available to the automotive manufacturers of today. These newer 250-300HP V6 engines can now be safely operated at extraordinarily low RPMs, RPMs that in the past, "near" past, would have put the engine's service life at risk to inadvertent (undetectable) knock/ping from, due to, lugging.

CVTs, coming soon to a car near you, will help.

*** There are now, often, due to the wider useful RPM range of these new (over-powered??) V6 engines, two actual O/D "hard" gear ratios available. Plus the O/D lockup clutch might be optionally used in the top 3, or even 4 "hard" gear ratios, resulting in a 9 or 10 speed gearbox. Use of the O/D lockup clutch now only changes the drive train's final drive ratio, but also results in sigificantly increasing FE due to the removal of the highly lossy torque converter being out of the loop.

What you are speaking of is "spark knock" caused by, as you explain wordily, ignition timing. I am speaking of knock caused by BMEP, which is the kind of detonation that destroys engines, and is caused by combustion chamber pressures exceeding the octane value and hence the knock resistance, of the fuel.

Your career in rocket science has failed you.

Pilotguy undestands BMEP as he is a pilot, like me.

I woke up at 2AM this morning and then couldn't get back to sleep because I got stuck thinking about your engine "detonation", high RPM and WOT.

Finally came to realize that with aircraft engines there ARE times you can go WOT with the engine already in a high RPM range.

Constant speed prop.....

A constant speed prop allows an aircraft engine to "idle" (virtually no engine load) near or even at maximum engine RPM.

And yes, an aircraft engine would probably self-destruct pretty quickly were you to move the prop from "cruise" to FULL bite without first enriching the mixture.

But I don't see how that translates into anything useful regarding fuel grade in automotive engines.

[PilotguyPA28]

Give me another week and I'll post the final results of city driving only. Last weekend I ended up going out of town and messed up the city driving test. I have about 1/3 tank used and so far it's 6% decrease in mileage with regular but I spent 6.4% less for the regular. Basically a wash. Seems there is a slight decrease in power when asking it to accelerate fast in town. This is with an '03 430LS.

Since I've only used 1/3 tank I'll post final results when I've used the whole tank for city driving. This is in a city of about 100,000 population. Some 1/2 - 1 mile non-stop stretches and some 1-2 block stretches. Not much bypass type driving. Hope that helps. I've seen it drop from 16.5 to 15.5 mpg.

[jcrome04]

Do you think it would be better to pay less money more often, or more money less often? heheh...

[Will B.]

If it turns out to be a wash or a couple percentage savings, is it really worth even the potential of problems? And if you do have problems, you are giving your warrany companies and potential out if they determine you were using fuel that is lower grade than specified in the manual.

[PilotguyPA28]

..................

[LEXUSA]

What year did Lexus start using knock sensors on the LS series?

[Vern Dias]

I'll put my money on both being very similar......I tried this when I first got my 2005 ES.....did not notice a single difference between the regular & higher octane grades.

But this isn't an ES forum.....

The Lexus V6 does not require premium gasoline.

The V8 requires premium, according to the owners manual.

So your experience is not applicable to the LS.

Vern