I saw a post here where someone mentioned that their father used only regular gas in their Lexus that called for premium. A person posted stating this would cause their cat converter to fail prematurely. I got no response to my questions on this older post, so I will re-ask it here; How does a lower grade of fuel cause problems for the cat converter? My son now has an '04 Acura TL and is using regular gas. If there is a real problem doing this I will suggest he pony up the additional .20 a gallon. Thanks.
Catalytic Converter - Regular vs. Premium
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I disagree about the cats failing if using regular. I believe using a diesel oil with high zinc will make it fail. That being said, I have the same generation TL and he should be using premium gas. It is a high compression engine. The manual states it. In fact your son is losing money since the engine is retarding timing to run on regular causing MPG to take a hit. Not to mention a performance hit as well. The TL forum did confirm that ultimately you might pay less at first to fill it with regular but you will burn it faster and pay more afterwards then just putting in premium and get the power and MPG Acura advertised.
I used to run regular in the 02 Volvo, that called for 91. started using 91 or better and MPG and performance improved. The 09 Volvo calls for regular but runs much better on mid grade. When it comes down to it its only a $2-$3 difference per fill up, well worth it.
gathermewool
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Best case, your son is losing some MPG's. Worst case, he's damaging his engine during times where the computer hasn't learned to pull timing or can't pull timing quickly enough. Even with the computer learning, it will still try to add the timing back to the knock threshold, then cut it again when it sense knock. This isn't a good cycle to be in.
As far as the cats, I can't see how this would affect them.
As far as the cats, I can't see how this would affect them.
Dumb question:
Are you sure you're all talking about the same thing? Regular vs. unleaded gas, and not 87 vs. 93 octane?
Not too long ago, 'regular' gas meant it still had lead in it, and that would surely kill a cat converter in short order.
Are you sure you're all talking about the same thing? Regular vs. unleaded gas, and not 87 vs. 93 octane?
Not too long ago, 'regular' gas meant it still had lead in it, and that would surely kill a cat converter in short order.
Where would you find that stuff besides at a airport?
Colt - Racetracks, special pumps for race gas, marinas, RV stops.
If that car is spec'd for premium, I'd use it for sure.
Not because of the cat - that is a non issue.
But because of the power loss, lower economy, and possible engine damage that could ensue with regular.
If that car is spec'd for premium, I'd use it for sure.
Not because of the cat - that is a non issue.
But because of the power loss, lower economy, and possible engine damage that could ensue with regular.
If regular unleaded damaged cats on premium cars you know they would come out with a keyed fuel filler and warnings plastered everywhere in the car. Look at how they've de-zinc-ed motor oil on the off chance that you'll burn some!
As said above the poor running is reason enough to use premium. The price delta as a percentage is less with $4 gas, and premium has a wider variation from station to station. So find a favorite one, get a credit card with 4-5% rebate, and cover the spread.
As said above the poor running is reason enough to use premium. The price delta as a percentage is less with $4 gas, and premium has a wider variation from station to station. So find a favorite one, get a credit card with 4-5% rebate, and cover the spread.
Originally Posted By: gathermewool
Best case, your son is losing some MPG's. Worst case, he's damaging his engine during times where the computer hasn't learned to pull timing or can't pull timing quickly enough. Even with the computer learning, it will still try to add the timing back to the knock threshold, then cut it again when it sense knock. This isn't a good cycle to be in.
I'm not sure I'd say that it's not a "good cycle". In fact, I'm not sure that I'd say it's a cycle at all. In most modern vehicles, the computer is advancing the timing enough, under any grade of fuel, so that it extracts the most performance and economy out of that fuel. Most modern engines are on the threashold of light spark knock at all times anyway, and spark timing adjustment is extremely fluid, and changing at all times. From that standpoint, it's not a cyclical process, but a continual one.
I'd wager that the Acura's engine would see even BETTER performance, and even BETTER mileage, if you ran a 95 or 100 octane fuel in it. But we don't have that at the pump, so they recommend to run "premium" fuel, because that's the best available. Recall that "premium" fuel isn't really a set-in-stone definition anyway. In some areas, premium is 90 octane. In others, it's 91. In others, it's 92 or 93.
I do agree that he should run premium fuel in it. Our '05 MDX, which specifies premium, certainly runs best on it. Coincidentally, my parents, when they owned it, only ran regular in it, and BOTH catalytic converters have been replaced on it. However, we believe that's due to an E85 conversion kit that dad briefly ran on the car. It never ran right with the kit, even though E85 fuel was never actually used in the car, and he had it removed after a few months. One of the converters was replaced when the kit was installed (no questions asked) and the other converter was replaced a few months after the kit was removed (again, no questions asked).
Best case, your son is losing some MPG's. Worst case, he's damaging his engine during times where the computer hasn't learned to pull timing or can't pull timing quickly enough. Even with the computer learning, it will still try to add the timing back to the knock threshold, then cut it again when it sense knock. This isn't a good cycle to be in.
I'm not sure I'd say that it's not a "good cycle". In fact, I'm not sure that I'd say it's a cycle at all. In most modern vehicles, the computer is advancing the timing enough, under any grade of fuel, so that it extracts the most performance and economy out of that fuel. Most modern engines are on the threashold of light spark knock at all times anyway, and spark timing adjustment is extremely fluid, and changing at all times. From that standpoint, it's not a cyclical process, but a continual one.
I'd wager that the Acura's engine would see even BETTER performance, and even BETTER mileage, if you ran a 95 or 100 octane fuel in it. But we don't have that at the pump, so they recommend to run "premium" fuel, because that's the best available. Recall that "premium" fuel isn't really a set-in-stone definition anyway. In some areas, premium is 90 octane. In others, it's 91. In others, it's 92 or 93.
I do agree that he should run premium fuel in it. Our '05 MDX, which specifies premium, certainly runs best on it. Coincidentally, my parents, when they owned it, only ran regular in it, and BOTH catalytic converters have been replaced on it. However, we believe that's due to an E85 conversion kit that dad briefly ran on the car. It never ran right with the kit, even though E85 fuel was never actually used in the car, and he had it removed after a few months. One of the converters was replaced when the kit was installed (no questions asked) and the other converter was replaced a few months after the kit was removed (again, no questions asked).
Whats the elevation there in Wisconsin? You can reduce the octane rating as your elevation increases. (Does not include turbo or supercharged engines) Around here you can drop 2 octane points with no ill effects.
I disagree with you people re; the cat. on regular fuel,when Premium is recommended. In Lexus vehicles anyway,the amount of unburned fuel going into the system is what eventually kills them. I can always tell when I`m following another Lexus, especially up hills, if they are burning 87 octane, Just by the smell. As Lionel would say on WPIX..."comment as you see fit"
^ All new-ish Toyotas seem to do that. As soon as you give it a decent bit of throttle, especially merging onto the highway, hello cat stech due to the gobs of excess fuel being poured into the engine. The high throttle fuel enrichment on them is far more aggressive than most other cars, and especially compared to older vehicles.
Originally Posted By: rslifkin
^ All new-ish Toyotas seem to do that. As soon as you give it a decent bit of throttle, especially merging onto the highway, hello cat stech due to the gobs of excess fuel being poured into the engine. The high throttle fuel enrichment on them is far more aggressive than most other cars, and especially compared to older vehicles.
Right, plus it`s magnified using lower octane fuel.I have no smell`s using premium. When I experimented on regular, the smell was real bad, carbon looking junk on the tailpipe (totally clean now) lost 2mpg`s, less power/smoothness.
^ All new-ish Toyotas seem to do that. As soon as you give it a decent bit of throttle, especially merging onto the highway, hello cat stech due to the gobs of excess fuel being poured into the engine. The high throttle fuel enrichment on them is far more aggressive than most other cars, and especially compared to older vehicles.
Right, plus it`s magnified using lower octane fuel.I have no smell`s using premium. When I experimented on regular, the smell was real bad, carbon looking junk on the tailpipe (totally clean now) lost 2mpg`s, less power/smoothness.
Originally Posted By: lexus114
I disagree with you people re; the cat. on regular fuel,when Premium is recommended. In Lexus vehicles anyway,the amount of unburned fuel going into the system is what eventually kills them. I can always tell when I`m following another Lexus, especially up hills, if they are burning 87 octane, Just by the smell. As Lionel would say on WPIX..."comment as you see fit"
87 burns more easily than 91. I'm not sure I understand what you mean.
I disagree with you people re; the cat. on regular fuel,when Premium is recommended. In Lexus vehicles anyway,the amount of unburned fuel going into the system is what eventually kills them. I can always tell when I`m following another Lexus, especially up hills, if they are burning 87 octane, Just by the smell. As Lionel would say on WPIX..."comment as you see fit"
87 burns more easily than 91. I'm not sure I understand what you mean.
^^^ Well for one thing the ecm richens up the fuel mixture as well as cut back on the timing in the attempt to keep it from pinging,that`s where the unburned fuel come`s into play.
gathermewool
Site Donor 2023
Originally Posted By: Hokiefyd
Originally Posted By: gathermewool
Best case, your son is losing some MPG's. Worst case, he's damaging his engine during times where the computer hasn't learned to pull timing or can't pull timing quickly enough. Even with the computer learning, it will still try to add the timing back to the knock threshold, then cut it again when it sense knock. This isn't a good cycle to be in.
I'm not sure I'd say that it's not a "good cycle". In fact, I'm not sure that I'd say it's a cycle at all. In most modern vehicles, the computer is advancing the timing enough, under any grade of fuel, so that it extracts the most performance and economy out of that fuel. Most modern engines are on the threashold of light spark knock at all times anyway, and spark timing adjustment is extremely fluid, and changing at all times. From that standpoint, it's not a cyclical process, but a continual one.
I'd say that it most certainly is a cycle, in that the ECM has a maximum amount of timing that it would like to add, which is based on variables such as, but not limited to, engine load and RPM. While using premium fuel, even 93 octane where 91 is specified, may result in instances of knock, either from true knock events or noise the ECM perceives as knock. If no knock is detected, the ECM will add as much timing as it can, but can't exceed the maximum value that it pulls from a lookup table. This means that a happy engine that runs fine on 91 octane will add, let's say, a max of 5 degrees of timing, but won't go higher than that if you switch to 93 octane instead.
For sporadic knock events, the ECM will pull timing only in that instance, but will maintain full timing the next time the engine is running at that specific load and RPM. In this instance, the engine is still happy and adding the maximum amount of timing it can, but has taken away some of that timing to combat the knock event. This is called feedback knock correction.
To account for knock events that happen often, timing is reduced in that cell so that timing will always be retarded for that particular cell. This is the ECM trying to predict when a knock event will occur and preemptively retard timing. This is the learned knock correction.
If the knock is bad enough, say when you run 87 octane for a car tuned specifically for 93 octane, the overall timing advance will be retarded, not just the learned knock correction.
The ECM is smart like this for a few reasons: 1. If you happen to get some poo gas; 2. If you happen to intentionally or unintentionally fillup with a lower-than-required octane; and 3. to account for sudden temperature and elevation changes. The third one is covered by other variables in the ECM, but I've seen knock events on unusually cold mornings, when there were none the previous, warm day.
While the ECM is very quick to pull timing, it still requires knock events to occur before it will do so, and if it hasn't seen any knock in a while, it will run full timing. This is bad for those who drive cars requiring premium, but switch up between premium and regular frequently. The ECM will pulling timing and then adding it back with every fillup. While this might not cause SUBSTANTIAL damage, if any at all, it does increase the risk.
Not only does added timing increase horsepower, it also increases gas mileage. Allowing the ECM to add as much timing as it wants to is worth the extra $2-4 per fillup, and required for some to prevent engine damage.
Originally Posted By: gathermewool
Best case, your son is losing some MPG's. Worst case, he's damaging his engine during times where the computer hasn't learned to pull timing or can't pull timing quickly enough. Even with the computer learning, it will still try to add the timing back to the knock threshold, then cut it again when it sense knock. This isn't a good cycle to be in.
I'm not sure I'd say that it's not a "good cycle". In fact, I'm not sure that I'd say it's a cycle at all. In most modern vehicles, the computer is advancing the timing enough, under any grade of fuel, so that it extracts the most performance and economy out of that fuel. Most modern engines are on the threashold of light spark knock at all times anyway, and spark timing adjustment is extremely fluid, and changing at all times. From that standpoint, it's not a cyclical process, but a continual one.
I'd say that it most certainly is a cycle, in that the ECM has a maximum amount of timing that it would like to add, which is based on variables such as, but not limited to, engine load and RPM. While using premium fuel, even 93 octane where 91 is specified, may result in instances of knock, either from true knock events or noise the ECM perceives as knock. If no knock is detected, the ECM will add as much timing as it can, but can't exceed the maximum value that it pulls from a lookup table. This means that a happy engine that runs fine on 91 octane will add, let's say, a max of 5 degrees of timing, but won't go higher than that if you switch to 93 octane instead.
For sporadic knock events, the ECM will pull timing only in that instance, but will maintain full timing the next time the engine is running at that specific load and RPM. In this instance, the engine is still happy and adding the maximum amount of timing it can, but has taken away some of that timing to combat the knock event. This is called feedback knock correction.
To account for knock events that happen often, timing is reduced in that cell so that timing will always be retarded for that particular cell. This is the ECM trying to predict when a knock event will occur and preemptively retard timing. This is the learned knock correction.
If the knock is bad enough, say when you run 87 octane for a car tuned specifically for 93 octane, the overall timing advance will be retarded, not just the learned knock correction.
The ECM is smart like this for a few reasons: 1. If you happen to get some poo gas; 2. If you happen to intentionally or unintentionally fillup with a lower-than-required octane; and 3. to account for sudden temperature and elevation changes. The third one is covered by other variables in the ECM, but I've seen knock events on unusually cold mornings, when there were none the previous, warm day.
While the ECM is very quick to pull timing, it still requires knock events to occur before it will do so, and if it hasn't seen any knock in a while, it will run full timing. This is bad for those who drive cars requiring premium, but switch up between premium and regular frequently. The ECM will pulling timing and then adding it back with every fillup. While this might not cause SUBSTANTIAL damage, if any at all, it does increase the risk.
Not only does added timing increase horsepower, it also increases gas mileage. Allowing the ECM to add as much timing as it wants to is worth the extra $2-4 per fillup, and required for some to prevent engine damage.
^^^^^ Yep, what he said
^^^^
Now that I think about it... I should have my dad try a tank of 93 in his 05 Camry V6. His tailpipe is definitely sooty, and it stinks like heck if I'm driving behind him and he goes WOT. It doesn't ping though, and runs like a champ with about 125k miles on it (he drives a lot).
^^^ Tel him to try about three tanks, clean the tail pipe, and I bet it stays clean. Well, if he kept using premium anyway. Even the 89 isnt a bad choice.
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