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Car Forum / Lexus Cars / August 2007lower octane gasoline
This is just a curiosity question. I've always wondered why some cars require high octane gasoline and others do not. I have a 350GS and always use the highest octane as required, but the one time I goofed and did not, the engine did not "knock" or do anything else. What really happens in the engine when a lower octane is used and why would engines be designed to not use them instead of be designed to use them? Jeff > This is just a curiosity question. > [quoted text clipped - 8 lines] > > Jeff Some vehicles require high octane because the engines have a high compression ratio. High compression engines will not run properly on lower octane fuel and engine damage can result from the use of improper fuel. Some other engines have more advanced ignition timing to improve performance, and the higher octane fuel allows more advanced ignition timing. The advent of electronic spark advance and now distributor-less ignition allows a much wider range of ignition timing, and combined with knock sensors, the car's computer can retard timing to allow the use of lower octane fuel, with the tradeoff being slightly less performance and fuel economy.  SignatureRay O (correct punctuation to reply) RayO, Do you have an opinion on the effects of premium and regular on how some of the transmission shift on our Lexus's? thanks >> This is just a curiosity question. >> [quoted text clipped - 20 lines] > lower octane fuel, with the tradeoff being slightly less performance and > fuel economy. > RayO, > Do you have an opinion on the effects of premium and regular on how some > of the transmission shift on our Lexus's? I have heard but not read first-hand of a technical service bulletin that recommended using permium fuel to improve transmission shifting on vehicles with delayed shifting. Using premium fuel will apparently help but not necessarily eliminate the delayed shifting. SignatureRay O (correct punctuation to reply) How could premium fix a bad engineered tranny??? > > RayO, > > Do you have an opinion on the effects of premium and regular on how some [quoted text clipped - 4 lines] > with delayed shifting. Using premium fuel will apparently help but not > necessarily eliminate the delayed shifting. The answer is that premium CANNOT fix it. I had a 2002 ES with that crappy trans. Nothing they did (resets, etc) could fix it. When they performed TSIB TC004-03 I felt it was better for a few weeks, but then the hesitation and slamming shifts returned. Such garbage from Lexus/Toyota Engineering is a disgrace. Hopefully, everyone who signed off on that poorly-engineered trans was fired. Those still there who continue to say "No problem exists" should be fired as well. Anyhow, I have a copy of the TSIB, and it is clearly noted (in a box bordered in RED) on the last page that one should : "Select premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher ... " I did that - NG. I no longer own the car ....... On 7/16/07 5:32 PM, in article xeadnSHO3K_MfgbbnZ2dnUVZ_hmtnZ2d@comcast.com, How could premium fix a bad engineered tranny??? So using the super duper hi test ethyl gas, I get 14.5 mpg around town. If I change to the lower octane regular, what will my milage decrease to? > How could premium fix a bad engineered tranny??? In a previous question, I had mentioned how a Maryland Lexus service rep. had recommended I stop using premium ( I had complained to him about my sooty tailpipes and he said using regular would stop sooty deposits)..... well 5000 miles later, the soot is starting to disappear, and my mileage with regular gas seems to have improved, especially in highway driving. The reason I bring this up is that I had a problem with the transmission: when I came to a stop and then stepped on the gas, the car would hesitate. I brought it to my New York Lexus service rep's attention and he said that this problem could not be solved, I would have to live with it, because of the way the transmission ECU was set. Now lo and behold, I forgot about this annoyance and guess what! Since I have been using regular, the car or transmission no longer hesitates after I come to a stop and want to step on the gas again. Just wanted to share my experiences with my 2006 GS300 AWD; right now my main gripe is that the car is underpowered, unless I get aggressive with the gas pedal, in which case it downshifts (a lot) and really moves. Another mild gripe, the car used almost a quart of oil in 5000 miles, then I added half a pint and the dipstick reads half full.......... I never had such a quirky dipstick and why does it have to be so long...... How could premium fix a bad engineered tranny??? Some comments on the topic: when I complained about my car hesitating when I come to a full stop and then immediately step on the gas, my Lexus service rep. said it could not be fixed, it had to do with the ECU settings in the transmission. I also complained about sooty tail pipes and he just said it was not important. Then at 20K miles, I went to another dealership with my 2006 GS300 AWD and complained about sooty pipes. The service rep at that Lexus dealership recommended I use regular instead of premium gas. Net result is that my mileage improved, especially for highway travel, and after 5K miles the pipes appear to be loosing the black soot that was there prior. I never personally cleaned the pipes. Then lo and behold, a funny thing happened, I had forgotten about it until the subject of tranny hesitation was brought up again: My car no longer hesitates after I come to a full stop and want to get moving again. Other than that I have only two beefs: (1) not enough power, unless I get aggressive with the gas pedal, in which case the transmission is often downshifting, and (2) The dipstick showed I had used almost a quart of oil atfter 5K, when I added a half pint, the dipstick read on the halfway mark; wish the dipstick were not as long and was more accurate. Pleased as punch > How could premium fix a bad engineered tranny??? >> [quoted text clipped - 8 lines] >> with delayed shifting. Using premium fuel will apparently help but not >> necessarily eliminate the delayed shifting. I don't know for sure. From what I've read, the problem is more with the transmission ECU's programming than the mechanics/hydraulics of the transmission itself. The transmission ECU uses inputs from several sensors, probably including ignition timing. SignatureRay O (correct punctuation to reply) Ray, Does it harm a 05 ES 330 to switch back and forth between premium and regular gas? Lately, I've been considering the price. Al >> RayO, >> Do you have an opinion on the effects of premium and regular on how some [quoted text clipped - 4 lines] > vehicles with delayed shifting. Using premium fuel will apparently help > but not necessarily eliminate the delayed shifting. > Does it harm a 05 ES 330 to switch back and forth between premium and > regular gas? Check your owner's manual. Lexus is good about telling you if it's perfectly OK not to use premium gas. Please tell me why people buy luxary cars if they can't afford the gas? It is a LUXARY CAR. It is for people who can afford them. > Ray, > Does it harm a 05 ES 330 to switch back and forth between premium and [quoted text clipped - 9 lines] >> vehicles with delayed shifting. Using premium fuel will apparently help >> but not necessarily eliminate the delayed shifting. > Please tell me why people buy luxary cars if they can't afford the gas? > It is a LUXARY CAR. It is for people who can afford them. Frequently, the "premium" recommendation from the mfr is simply to cater to the idea that "I bought a luxury car, it doesn't take anything as PLEBIAN as REGULAR gas". The whole idea of "regular" and "premium" gas is just so much hooey. "Premium" gas isn't premium at all. It simply is a higher octane gas. That doesn't denote a "premium" fuel at all. There really is no such thing as a "premium" fuel. So if your mfr states that you may run the car on 87 octane (as Lexus used to do, at least), and if you get good gas mileage (sometimes 87 octane fuel gives better mileage than 93), then who cares? I don't recall saying that I couldn't afford it. I simply want to know if I can sometimes minimize being ripped off at the pump. Besides, I have read often enough that many people waste money when they buy "premium" instead of using regular. My question was whether there is any harm in switching back and forth, or should I select one grade and stick with it? Now, if buying premium instead of regular for your Lexus makes you feel better, fine. Al > Please tell me why people buy luxary cars if they can't afford the gas? > It is a LUXARY CAR. It is for people who can afford them. [quoted text clipped - 12 lines] >>> vehicles with delayed shifting. Using premium fuel will apparently help >>> but not necessarily eliminate the delayed shifting. I have heard that it is generally not a good idea to switch back and forth between grades, but doubt that it is harmful. I believe using higher grade does give you slightly more power, and sometimes better fuel mileage, but it didn't work out to be much different on my 2005 ES 330. I now use 87 octane all the time. Bob >I don't recall saying that I couldn't afford it. I simply want to know if >I can sometimes minimize being ripped off at the pump. Besides, I have [quoted text clipped - 21 lines] >>>> vehicles with delayed shifting. Using premium fuel will apparently >>>> help but not necessarily eliminate the delayed shifting. > I believe using higher grade does give you slightly more > power, and sometimes better fuel mileage, but it didn't > work out to be much different on my 2005 ES 330. > I now use 87 octane all the time. I switched to high octane (93) for my 2004 ES330 about a year or 2 ago. The increased cost is mostly paid for by improved gas mileage. Some here have said they get about a 1 mpg increase in gas mileage. Based on the onboard computer, my experience correlates. Also, while the higher octane gas doesn't eliminate the hesitating/jerky transmission entirely, it reduces the problem significantly. But, as the say, YMMV. >I don't recall saying that I couldn't afford it. I simply want to know if >I can sometimes minimize being ripped off at the pump. Besides, I have [quoted text clipped - 4 lines] >better, fine. > Al If the car is designed to run primarily on regular fuel, then IMO, it is a waste of money to use premium. On the other hand, my experience with my LS 400 and LS 430 is that I get a performance and fuel economy benefit from using premium, so that cost-wise, it is a wash to use premium, with the bonus of a little more performance from the premium. SignatureRay O (correct punctuation to reply) > If the car is designed to run primarily on regular fuel, then IMO, it is a > waste of money to use premium. On the other hand, my experience with my LS > 400 and LS 430 is that I get a performance and fuel economy benefit from > using premium, so that cost-wise, it is a wash to use premium, with the > bonus of a little more performance from the premium. It's easy enough to evaluate the fuel cost per mile, but most people don't do it. > It's easy enough to evaluate the fuel cost per mile, > but most people don't do it. I agree that it's easy to do, but not so easy to do it accurately. Driving patterns differ from tank to tank. > > It's easy enough to evaluate the fuel cost per mile, > > but most people don't do it. > > I agree that it's easy to do, but not so easy to do it accurately. > Driving patterns differ from tank to tank. Accurately enough, if you generally do the same type of driving throughout the test, use up full tankfuls, and fill up at the same pump each time. > > > It's easy enough to evaluate the fuel cost per mile, > > > but most people don't do it. [quoted text clipped - 5 lines] > throughout the test, use up full tankfuls, and fill up at the same pump > each time. I seriously question the accuracy of that technique. The part I question is "do the same type of driving throughout the test." Too many variables here (e.g., ratio of highway vs. local driving, rate of acceleration, etc.). >> > > It's easy enough to evaluate the fuel cost per mile, >> > > but most people don't do it. [quoted text clipped - 11 lines] > variables here (e.g., ratio of highway vs. local driving, rate of > acceleration, etc.). For a meaningful comparison without the benefit of tightly controlled conditions, the comparison should be with at least a month's worth of driving on premium and then a month's worth of driving on regular, using a fixed price for regular and premium. My experience is that there was no significant cost difference per mile driven. SignatureRay O (correct punctuation to reply) To all contributors to this thread, this is actual mileage, as I keep a log of $ and gallons used with my credit card chits (gal. accuracy to three decimals). For 2005-06, when my 2006 GS300 AWD was brand new, I got 27.011 mpg average for 12000 + of driving mostly once a week, long trip and mostly highway. For 2006-07, after I switched from Premium to Regular (87 octane), same type of driving, also about 12K miles, I got 28.266 mpg. You cannot argue with numbers. The only difference I could feel was a slight loss of power and more downshiftings by the transmission. > To all contributors to this thread, this is actual mileage, as I keep > a log of $ and gallons used with my credit card chits (gal. accuracy [quoted text clipped - 7 lines] > You cannot argue with numbers. The only difference I could feel was a > slight loss of power and more downshiftings by the transmission. But really, the ONLY measure you SHOULD use is the cost per mile for fuel. Yes, in your case, your MPG went up when you used CHEAPER gas, so there's no doubt that your fuel cost per mile is lower using 87 octane. But others may need to see the actual fuel cost per mile in order to see that in other cars, the fuel that's more expensive to buy--maybe it's name brand vs. grocery store gas, or maybe it's higher octane vs. lower octane--is actually cheaper to run. > Yes, in your case, your MPG went up when you used CHEAPER gas, so > there's no doubt that your fuel cost per mile is lower using 87 octane. > But others may need to see the actual fuel cost per mile in order to see > that in other cars, the fuel that's more expensive to buy--maybe it's > name brand vs. grocery store gas, or maybe it's higher octane vs. lower > octane--is actually cheaper to run. OK, since there is interest in the mpg subject, here are my actual numbers, although the mileage is almost identical, they are real numbers: from Aug '05 when my GS330 was new to Aug '06, I drove 12505 miles and spent $1364 for fuel to get 27 mpg. The next year, from Aug '06 to Aug '07, I drove 12509 miles, spent $1272 for fuel (price per gal went up too) and got 28.26 mpg. By my math, I used 463.15 gals the first year, and only 442.64 the following year. At $3 a gal, all things being equal, I did not save much, about $60.... Had I stuck with Premium however, I would have paid an extra 30 cents per gal times 463.15 = $139 for a total savings of $139 + $60, or about $200.... BTW, savings would be more significant if I drove less highway and more city where my mpg would have dropped to 21 or 23.... just wanted to share this with you.. >> Yes, in your case, your MPG went up when you used CHEAPER gas, so >> there's no doubt that your fuel cost per mile is lower using 87 octane. [quoted text clipped - 16 lines] >highway and more city where my mpg would have dropped to 21 or 23.... >just wanted to share this with you.. A new car almost always gets poorer gas mileage than one that has had about 10K or more miles put on it. Also, until you get used to the feel of the gas pedal and brakes on a new car, you will also tend to drive less smoothly than when the car feels like "an old glove". Try switching back to medium grade (89 or 91 octane) and see if you don't get better mileage than with regular, like most car owners. You may even find that your cost per mile goes down -- many do. SignatureJay (remove dashes for legal email address) >Please tell me why people buy luxary cars if they can't afford the gas? >It is a LUXARY CAR. It is for people who can afford them. What is a LUXARY CAR? DaveW asks.... "What is a LUXARY CAR?" Answer... check with McBrue. But if you are asking about a LUXURY CAR., then Wikipedia definds the term this way.... A luxury vehicle is a relatively expensive vehicle which includes additional features designed to increase the comfort of the driver and passengers. Luxury vehicles usually place more emphasis on comfort, appearance, and amenities such as technological upgrades and higher quality materials than on performance, economy, or utility. Luxury vehicles are often built in smaller numbers than more affordable mass-market vehicles. Luxury vehicles include cars (sedan, coupé, hatchback, station wagon, roadster, etc.) and trucks, such as light pickup trucks or sport utility vehicles. But their definition may be considered hog wash because they go on to proclaim "The Flagship Of Luxury, The Lincoln Town Car!" I think I'll stick to my rice-burner. Larry In the back yard, under the oak. If I couldn't afford it, I wouldn't have bought it, but I don't like overpaying on anything. Do you? Al > Please tell me why people buy luxary cars if they can't afford the gas? > It is a LUXARY CAR. It is for people who can afford them. [quoted text clipped - 12 lines] >>> vehicles with delayed shifting. Using premium fuel will apparently help >>> but not necessarily eliminate the delayed shifting. > Ray, > Does it harm a 05 ES 330 to switch back and forth between premium and > regular gas? Lately, I've been considering the price. > Al It doesn't hurt to switch back and forth between premium and regular gas, but after you have used regular gas, it can take a couple of tanks of premium before the advantage from premium is re-gained because it may take that long for the computer to realize that it is "safe" to advance the ignition timing enough to take advantage of the higher octane. My recommendation would be to pick one grade and stick to it. SignatureRay O (correct punctuation to reply) > >>> RayO, [quoted text clipped - 5 lines] >> vehicles with delayed shifting. Using premium fuel will apparently help >> but not necessarily eliminate the delayed shifting. Why pay $ 60,000 for a car then put regular gas in it so it runs like a $20,000 car? And then to top it off listen to someone on the internet , which you do not know their reliability? Doesn't make sense to me. >> Ray, >> Does it harm a 05 ES 330 to switch back and forth between premium and [quoted text clipped - 20 lines] >>> vehicles with delayed shifting. Using premium fuel will apparently help >>> but not necessarily eliminate the delayed shifting. > Why pay $ 60,000 for a car then put regular gas in it so it runs like a > $20,000 car? Why pay more for gas if the lower octane (and lower cost) fuel DOESN'T cause it to run any differently? But undoubtly you don't know the it will run the same and will not hurt your car. If not all these people wouldn't be sending in messages regarding the subject. >> Why pay $ 60,000 for a car then put regular gas in it so it runs like a >> $20,000 car? > > Why pay more for gas if the lower octane (and lower cost) fuel DOESN'T > cause it to run any differently? > But undoubtly you don't know the it will run the same and will not hurt your > car. Like I said, check your owner's manual. If the owner's manual says 87 octane is fine and won't cause damage, then go to the next step--run several tankfuls, see what you think, and see what your fuel cost per mile is compared to doing the same thing with 93 octane fuel. If 87 does no damage and you like what 87 octane does for you, then who cares what you run? |
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