LEXIE Posted June 30, 2004 Share Posted June 30, 2004 I would really like to get a simplified answer with some technical backing regarding the choice of octane level I am presently using in my '93SC400. Several months ago a reputable car analyst, Bobby Likis, who has a national talk show said that if you are not a performance bug you can use a lower octane gas w/o harming your car. I have since gone from full bore 93 oct to 87 and have not seen any loss of performance even when I press the car. I am a predominately town driver and rarely get my rpm's above 2000. I hear comments like if you can afford a Lexus then why worry about the extra cost to go high oct or, the Lexus people highly recommend max oct level for max performance..sure what else could they say.. and your car has an automatic sensor to adjust timing to oct level curently being used(i like that that little deal) so thats why you dont hear pinging when you "push" it. Neat design feature. Well, because I worried about a penny here and a penny there made it possible for me to own the Lexus I have today so yes my nature says 20 cents per gallon is important especially when I see not one sign of deterioraton in my old- man style of driving. And yes, if being purist in nature and going strictly by what the Lexus manual says makes you feel more confident well I can understand that issue. Other than opinion, can someone confidently say that I am going to carbonize my engine, screw my valves up, overload the system, etc.. by using lower octane or is it just a subtle loss in performance, which I don't really care about, when using lower oct gas. L Quote Link to comment Share on other sites More sharing options...
jragosta Posted June 30, 2004 Share Posted June 30, 2004 I would really like to get a simplified answer with some technical backing regarding the choice of octane level I am presently using in my '93SC400.Several months ago a reputable car analyst, Bobby Likis, who has a national talk show said that if you are not a performance bug you can use a lower octane gas w/o harming your car. I have since gone from full bore 93 oct to 87 and have not seen any loss of performance even when I press the car. I am a predominately town driver and rarely get my rpm's above 2000. I hear comments like if you can afford a Lexus then why worry about the extra cost to go high oct or, the Lexus people highly recommend max oct level for max performance..sure what else could they say.. and your car has an automatic sensor to adjust timing to oct level curently being used(i like that that little deal) so thats why you dont hear pinging when you "push" it. Neat design feature. Well, because I worried about a penny here and a penny there made it possible for me to own the Lexus I have today so yes my nature says 20 cents per gallon is important especially when I see not one sign of deterioraton in my old- man style of driving. And yes, if being purist in nature and going strictly by what the Lexus manual says makes you feel more confident well I can understand that issue. Other than opinion, can someone confidently say that I am going to carbonize my engine, screw my valves up, overload the system, etc.. by using lower octane or is it just a subtle loss in performance, which I don't really care about, when using lower oct gas. L There's one major thing to watch for - ping or knock. If your engine is knocking, move up to a higher grade of gasoline. If it's not knocking, you should be OK. If there's any doubt, I'd move up one grade. You really don't want knocking going on. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted June 30, 2004 Share Posted June 30, 2004 Higher octane will be better over the long run for maximum engine variability to burn as much fuel as needed. It lets the ecu make the descion to change the timing of ignition in regards to load , and what it can make out of the fuel. I find i get way better mileage and power form using 93 octane in my cars an average of 50-80 km extra a tank Lower octane also uses cheaper additives and cleaners which all gas has , which if used often cause the systems to build up with carbon much easier and not be removed causing knock later on especially if not revved hard and somewhat often to break off the carbon. Quote Link to comment Share on other sites More sharing options...
jzz30 Posted June 30, 2004 Share Posted June 30, 2004 the higher octane is for added insurance from knock and ping as well as performance and as SK says for better milage. Quote Link to comment Share on other sites More sharing options...
LEXIE Posted June 30, 2004 Author Share Posted June 30, 2004 skp 80 km per tank is a significant gain in miles/gal..approx 2.5 if you assume a 20 gal tank. this would make it a wash if i were saving say 20 cents per gallon less for 87 vs 93 at approx $2/gal. so, if i were to experience the same gain/loss in mpgal..depending on which octane i were using.. then it is obvious that i would be better off sticking with the high oct and not having to worry about potential problems cropping up while at the same time maintaing peak perf. i guess i will have to do a mileage check but i suspect my difference between the two grades will not be as significant due to my driving habits. if i see even a 1mpgal change, i will go back to the high oct. thx for the replys. L Quote Link to comment Share on other sites More sharing options...
soarer479 Posted June 30, 2004 Share Posted June 30, 2004 wow :chairshot: can we say carbon build up every where lower octane fuel not a good idea trust me Quote Link to comment Share on other sites More sharing options...
2XLexV8 Posted July 1, 2004 Share Posted July 1, 2004 Good Evening, I work in the service department of a small Toyota dealership. We also service Lexus. The #1 performance problem in our area is the fuel system. Lots of customers want to reduce thier fuel cost, but it's a "Pay me now or pay me later." relationship. Looking at a 15-gallon fill-up in a 20-gallon tank, the difference between 93 0ctane at $2.00/gal and 87 at $1.80/gal is $3.00. Yes, less than a Happy Meal. The above post about fuel quality is right on track. You get what you pay for. Lexus bases the maintenance schedule on normal driving with premium fuel. Using lower quality gas increases the frequency you need fuel filters, spark plugs, induction system cleaning, etc. The loss of performance is gradual. Sometimes adding a bottle of cleaner will help. Cost: ~$3.00 Hmmm. As our cars get older, they typically need more octane, not less. There are other ways in the posts here to improve mileage like: Replace the O2 sensors in cars over 120K, use iridium plugs, get a K&N air filter, keep the tires inflated, buy fuel from reputable dealers, switch to synthetic oil, etc. Each has their fans and opponents, but part of the joy of the SC-series cars is using the power occasionally and sometime just for fun. Please, spend the $3.00. Good Luck Quote Link to comment Share on other sites More sharing options...
AWJ Posted July 1, 2004 Share Posted July 1, 2004 Without reading those other replies, wich I'm sure are fine, know this. Your motor is 10:1 compression. That is high. It has two knock sensors. This will pull timing and at stock settings you should never see detonation. The thing is, the engine was designed to run on high octane. The low grade stuff is crap. It literally has garbage in it. This builds up and gums and craps the motor. The high test stuff even has crap in it that builds up. As far as I'm concerned, every gas station should sell 104. Most other cars run 8:1 or so. These are meant to run that cheapola gas. That is why your guy says don't sweat the high test. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted July 1, 2004 Share Posted July 1, 2004 As far as I'm concerned, every gas station should sell 104. *sniffles* that is the best JDM upgrade you could ever get. That is why we have 15 gallon drums of elf race fuel at the shop. Ohhhh it smells so nice. you shuold see the difference in my air fuel ratio meter between 91 and 93 octane alone. It runs a much wider and lean band with 93 than 91 which the motor dumps more into and runs rich trying to compensate. btw this is in my civic which has lots of gauges to moderate. Quote Link to comment Share on other sites More sharing options...
kyle0k Posted July 1, 2004 Share Posted July 1, 2004 well u guys said its bad mostly b\c of the carbon buildup everywhere,but if u push it evryonce in a while,liek go fast. that cleans out nearly all the carbon so is it really that bad then? Quote Link to comment Share on other sites More sharing options...
SKperformance Posted July 1, 2004 Share Posted July 1, 2004 you might clear a small amount of the carbon from the valves but the rest needs a constant amount of cleaning to keep it from depositing and sticking to itself.Just hink of a tail pipe when it gets black with carbon when new it is much easier to clean than when you leave it and it bakes itself into the metal and it almost impossible to remove as it is baked in . A good system is a motorvac to remove carbon once every other year to keep an engine in top efficency from removing carbon deposits. A fuel cleaner that is added to the gas tank is worthless if it costs less than $10 and even then it is only so good. Quote Link to comment Share on other sites More sharing options...
jzz30 Posted July 1, 2004 Share Posted July 1, 2004 yyeeeaaa race gas all the way baby! Quote Link to comment Share on other sites More sharing options...
LEXIE Posted July 1, 2004 Author Share Posted July 1, 2004 ok fellows, you have convinced me...going back to full bore 93 on next fill up. thx for all of the replies....maybe part of the reason i have only spent $2350 in total cost for maintenance and repairs over the past 12 yrs is due to use of high grade fuel. L Quote Link to comment Share on other sites More sharing options...
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