Anyone just use regualr gas in their GS?
03-26-10, 02:02 PM
#17
Driver School Candidate
Don't beat the guy up, all you ballers...
To answer your question, there are systems on the engine to prevent knock, misfires. When you run a lower octane (87 or 89) the gas may not burn as evenly or may cause a misfire. The lexus brain knows this and changes your mix, running the engine rich (more gas to air) and reduces your MPG....So running cheaper gas hurts your mileage and creates a slim chance you'll damage your engine. Prolly not worth it
If gas is kicking you in the shorts, fill $20 at a time and plan your trips in the GS better.
To answer your question, there are systems on the engine to prevent knock, misfires. When you run a lower octane (87 or 89) the gas may not burn as evenly or may cause a misfire. The lexus brain knows this and changes your mix, running the engine rich (more gas to air) and reduces your MPG....So running cheaper gas hurts your mileage and creates a slim chance you'll damage your engine. Prolly not worth it
If gas is kicking you in the shorts, fill $20 at a time and plan your trips in the GS better.
Point being... don't do it... terrible idea...
03-26-10, 02:03 PM
#18
I used to test gasolines for octane ratings at a company awhile ago (actually a long time ago), so bare with me.. Also, I hope this hasn't been covered by another thread since I haven't searched.
To test for an octane, I would run two tests and average the number to get the numbers you see at the pump ( 87, 89, and 91).
*it gets fuzzy here*
One test would basically be simulating a car driving on a flat plane with no resistance at a cruising speed of roughly 40mph (forgot the exact mph, but wasn't super duper fast). We would simulate this by having an engine with an adjustable head so we could cause knocking. When it would knock, we would record the readings. Usually you'd get a 100+ octane rating since there was no resistance and your car isn't struggling.
The other test was to simulate a car going up a hill of 30 degrees incline at 60 mph (again, not completely sure, but the set up of having resistance is right). The test would yield a lower octane rating of 70's to 80's.
Take the 2 numbers average them and you have your pump octane number (87, 89, 91). If you look at some of the pumps you'll actually see RON + MON avg on the stickers.
So point being, if you live in a relatively flat city, I don't see the need to run super high octane gas. I personally use mid grade gasoline and put supreme gas in after oil changes. I tend to stick to big name gas companies too. Some 2nd tier gases just meet bare minimum with some of the testing I've done and seen. If your wallet is hurt, don't worry to much.
To test for an octane, I would run two tests and average the number to get the numbers you see at the pump ( 87, 89, and 91).
*it gets fuzzy here*
One test would basically be simulating a car driving on a flat plane with no resistance at a cruising speed of roughly 40mph (forgot the exact mph, but wasn't super duper fast). We would simulate this by having an engine with an adjustable head so we could cause knocking. When it would knock, we would record the readings. Usually you'd get a 100+ octane rating since there was no resistance and your car isn't struggling.
The other test was to simulate a car going up a hill of 30 degrees incline at 60 mph (again, not completely sure, but the set up of having resistance is right). The test would yield a lower octane rating of 70's to 80's.
Take the 2 numbers average them and you have your pump octane number (87, 89, 91). If you look at some of the pumps you'll actually see RON + MON avg on the stickers.
So point being, if you live in a relatively flat city, I don't see the need to run super high octane gas. I personally use mid grade gasoline and put supreme gas in after oil changes. I tend to stick to big name gas companies too. Some 2nd tier gases just meet bare minimum with some of the testing I've done and seen. If your wallet is hurt, don't worry to much.
03-26-10, 03:45 PM
#19
I rolled thru Brooklyn NY last month on my way to a wake and filled up with 87 octane because the premium was like $4.25 a gallon. About a hundred miles later my Check Engine light came on. I puked an upstream O2 sensor, and I really think the 87 octane was to blame. Use the good stuff.
and last month it hadn't gone ANY where past the $3.25 mark even at the most expensive sunoco
03-26-10, 03:59 PM
#21
Driver School Candidate
iTrader: (2)
Join Date: Aug 2009
Location: MA
Posts: 40
Likes: 0
Received 0 Likes
on
0 Posts
87 octane here. 5+ years, 120k miles, and still going strong. I haven't had any issues at all. Except for probably the poor gas mileage I get(~18-19mpg). But that's acceptable to me.
03-26-10, 06:49 PM
#24
Driver School Candidate
Join Date: Sep 2008
Location: Montana
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
I always put premium gas in....always... i don't understand why not its not that much more expensive...If you drive a Lexus (or any foreign car for that matter) you should be prepared to pay more for everything. If not, you shouldn't have bought one! 
03-26-10, 08:40 PM
#26
Driver
Join Date: Jun 2008
Location: RVA
Posts: 102
Likes: 0
Received 0 Likes
on
0 Posts
I pay 30 cents over regular for premium, which is ~10%. When I use regular, I can sometimes lose ~10% in fuel economy. So it's a moot point, for me at least, shell out for the good stuff.
03-29-10, 07:52 PM
#28
Rookie
Join Date: Mar 2010
Location: HI
Posts: 79
Likes: 0
Received 0 Likes
on
0 Posts
I used to test gasolines for octane ratings at a company awhile ago (actually a long time ago), so bare with me.. Also, I hope this hasn't been covered by another thread since I haven't searched.
To test for an octane, I would run two tests and average the number to get the numbers you see at the pump ( 87, 89, and 91).
*it gets fuzzy here*
One test would basically be simulating a car driving on a flat plane with no resistance at a cruising speed of roughly 40mph (forgot the exact mph, but wasn't super duper fast). We would simulate this by having an engine with an adjustable head so we could cause knocking. When it would knock, we would record the readings. Usually you'd get a 100+ octane rating since there was no resistance and your car isn't struggling.
The other test was to simulate a car going up a hill of 30 degrees incline at 60 mph (again, not completely sure, but the set up of having resistance is right). The test would yield a lower octane rating of 70's to 80's.
Take the 2 numbers average them and you have your pump octane number (87, 89, 91). If you look at some of the pumps you'll actually see RON + MON avg on the stickers.
So point being, if you live in a relatively flat city, I don't see the need to run super high octane gas. I personally use mid grade gasoline and put supreme gas in after oil changes. I tend to stick to big name gas companies too. Some 2nd tier gases just meet bare minimum with some of the testing I've done and seen. If your wallet is hurt, don't worry to much.
To test for an octane, I would run two tests and average the number to get the numbers you see at the pump ( 87, 89, and 91).
*it gets fuzzy here*
One test would basically be simulating a car driving on a flat plane with no resistance at a cruising speed of roughly 40mph (forgot the exact mph, but wasn't super duper fast). We would simulate this by having an engine with an adjustable head so we could cause knocking. When it would knock, we would record the readings. Usually you'd get a 100+ octane rating since there was no resistance and your car isn't struggling.
The other test was to simulate a car going up a hill of 30 degrees incline at 60 mph (again, not completely sure, but the set up of having resistance is right). The test would yield a lower octane rating of 70's to 80's.
Take the 2 numbers average them and you have your pump octane number (87, 89, 91). If you look at some of the pumps you'll actually see RON + MON avg on the stickers.
So point being, if you live in a relatively flat city, I don't see the need to run super high octane gas. I personally use mid grade gasoline and put supreme gas in after oil changes. I tend to stick to big name gas companies too. Some 2nd tier gases just meet bare minimum with some of the testing I've done and seen. If your wallet is hurt, don't worry to much.
fwiw, in my little experience, fuel quality really comes into play when you're running high perf engines, high compression, high boost etc. I havent noticed too much a difference on any of my tame compression, NA (wife's ) cars. The GS300 seems to respond about the same to 87.
Interestingly, East coast 89, 91 and 93 were different than west coast 91. WEst Coast 91 is more similar to east coast 87-89 than anything near 91 in the east.
I derived all this from hours of logging my audi S4 in the east, and later in the west.
I have noticed a slight lethargy when using 87 instead of 91, the timing retardation would explain that.
good info here.
03-29-10, 08:15 PM
#29
Driver School Candidate
Join Date: Mar 2010
Location: California
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
I DONT use Regular, just like I dont use Aviation Fuel to make it go faster. Why not Kerosene? Water would be cheaper. And not that expensive bottled water but the free stuff out of your tap. Get my point? USE WHAT YOUR OWNERS MANUAL SAYS. If you a burning a hole in your pocket, better to siphon gas out of your neighbors car to help your pocket book, but be careful. Someone was siphoning gas around here, so I decided to booby trap my car...poured a bag of sugar into my gas tank...decided to do my neighbors a favor and poured a bag of sugar into their cars too. Guy who siphons our gas is gonna get a BIG Surprise now. Hahaha.
03-30-10, 03:21 AM
#30
I only use 93 in my 430.. but when i had my GS4 which was my DD i would switch it up occasionally. I do 90pct highway driving so it smooth cruising at about 80mph haha Reg. Mid or High test was all the same with my mileage i averaged 19.75mpg pretty much the whole life of the car that i owned it from 90-140k.. Just to be safe tho i would just stick with the 93 and geta DD that takes Regular..haha