Premium Gas vs Premium Gas (91 or 93)
11-30-18, 08:40 PM
#1
Driver
Thread Starter
Premium Gas vs Premium Gas (91 or 93)
Unlike the other gas recommendation threads, I am not going to ask if I could get away with putting regular gas in my GS. I love my Lexi and want the best for her. However, I observed something interesting (or maybe it is all in my head). I know the manual states that the car requires 91 minimum, but the only place by me that has 91 is Sunoco and they charge over $3.30 a gal. Seems to be a total rip as regular gas is relatively cheap ($2.60something) and they don't even post the prices to Plus and Premium until you pull up to the actual pump. Anyway, I have been sticking with Premium from Costco (93) which is just under $3.00. Today I was far away from Costco and needed to fill up. So I got 91 at Sunoco. I felt like the car ran much better - accelerated quicker and felt overall smoother. Is Costco not good gas, or is there that much of a difference between 91 and 93?
11-30-18, 09:50 PM
#2
It's all in your head. 93 just has more additives. The U.S. Environmental Protection Agency requires all commercially sold gasoline to contain engine cleaning detergent additives that can help extend the life of your vehicle. This means that your engine will be cleaned the same by 87 octane fuel as it will by 93 octane fuel. That being said the reason our GS require at minimum 91 but 93 is for optimum engine performance and driveability. Also keep in mind the ECU self adjust all the time. I also understand not all places give you the choice of 91 or 93 sometimes just 91.
12-01-18, 05:57 AM
#4
Driver School Candidate
When I bought my car (private party) I changed the plugs. The car ran fine before the plug Change but I could tell by changing the plugs that the individual who owned it seldom used premium gas . The center electrode was still a brown color but there was a lot more carbon build up on the plugs. Nothing too crazy the difference between 87 89 91 and 93 is the molecular chains in the gas 87 makes a more volitile flame front (more of a boom) in the combustion chamber vs 93 which is more of a sweeping explosion across the combustion chamber. 93 burns more efficiently and more complete than 87 And also hotter. The COmpression ratio usually dictates the octane used — if you have a car with an 11:1 compression ratio, and run a lower rated gas, depending on your engine speed the lower octane gas can combust before the top of the engine stroke or combust multiple times in the cylinder causing what is affectionately dubbed as engine knock. Cars with knock sensors may pull spark timing to Compensate for this. On forced induction vehicles running lower rated gas can destroy your engine rather quickly —getting back to the thread all gas has detergents in them but there is a minimal cleaning effect that may happen using 93 as it burns a bit hotter that 87 and more completely which can help reduce carbon build up. Comparing 91 and 93 The effects are neglegable on the Lexus
Last edited by tank3176; 12-01-18 at 06:36 AM.
12-01-18, 07:12 AM
#5
Driver School Candidate
It's interesting that you said that your GS ran better on Sunoco 91 gas vs. Costco 93. I'm wondering if the the Sunoco gas that you purchased was 100% gasoline compared to most other stations selling a gasoline ethanol blend. Your gas mileage should be better on the "pure" gas from Sunoco.
12-02-18, 05:57 PM
#6
Do they run a winter blend of fuel out there?
When ever we switch back to summer blend, I always feel like my cars have more pick up and i average better mpg.
When ever we switch back to summer blend, I always feel like my cars have more pick up and i average better mpg.
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12-03-18, 06:10 AM
#8
Probably more placebo effect than anything else. You used the costco stuff for X period of time. You just put the gas in and drove the car. Now you have used a different station and paid more money- mentally, your brain WANTS something good to happen, because you paid the money. Now you are, subconsciously, paying more attention to how the car runs, etc. Something like that. The only real way there could be a perceptible difference is if the costco tanks were contaminated or something (eg, wrong octane fuel in wrong tank, or excess water in tank, etc) but I think if that was actually the case, you'd likely notice much greater issues.
I go back and forth between Shell Vpower 93 and generic 93 (mostly based on where I need to get gas) and I really don't see a difference in performance. Once in a blue moon I've seen slight changes in MPGs between fuel types but again, this is probably a placebo too, because I may not be driving exactly the same way or run into the same traffic conditions with the "fuel that did really well".
-Mike
I go back and forth between Shell Vpower 93 and generic 93 (mostly based on where I need to get gas) and I really don't see a difference in performance. Once in a blue moon I've seen slight changes in MPGs between fuel types but again, this is probably a placebo too, because I may not be driving exactly the same way or run into the same traffic conditions with the "fuel that did really well".
-Mike
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