thermal

The recommended is premium unleaded, but with the price of gas going up, do any of you 'cheat' and use regular?

Will it harm the engine to use lower-octane gas?

ultra63

For this car 5% more for gas gives 5% more performace. It won't hurt the engine to go low test but you do get what you pay for according to a study done in a car magazine a while back. on 89 vs 93 octane.

lspower

93 or 94, i tried 100 before.
no ive never cheated and used anything less, it WILL knock like crazy, so you could be cheap and use lower octaine but it will sound like ***** and will be less powerful

RA40

iTrader: (6)

You get what you pay for...I've tested it in mine on the same stretch of road from So Cal to Eugene, Oregon.

Premium 91-28 MPG
Midgrade 89-24 MPG
Regular 87-20 to 21 MPG

The cost all works to be relatively the same to achieve what I could get on a full tank of 91. IMO, not worth the time. Now if I dump in 5 gallons or so of midgrade with the 91, I have not detected an obvious difference. But the PITA to switch isn't worth saving $.20-$.50.

xravexboix

20 cents more x 20 gallons is about $4 per tank (assuming it's a 20 cent increase)

Would you rather pay $4 more and be assured it's ok, or save $4 and possibly end up spending a lot more to replace knock sensors and any other things that may die =P

I love my low compression Solara... good ol' 9.6 =]

MRLEXO

good point. I say premium all the way. If you drive a lexus then you can afford premium. it is a premium car

chicagoblknazn

I get the highest octane available whereever I am. Usually Shell or BP. It's only a few cents more and my baby is worth it. You treat the car right...it'll treat you right.

hyperopt

Wow, that is a wide spread in mileage with different octanes. 28MPG is much higher than EPA estimate for highway driving.
I also tested mileage for regular and premium gas for the same stretch of highway for many months and found no difference between the two. I consistently got 24+-.5MPG (EPA estimated 23MPG).

GRAND_LS 4

iTrader: (2)

93 all the way.

matthaven

While I generally use only 93 octane, you can do the math and see that alternating between 89 and 93, and filling up when you reach the half way mark will give you an average in tank octane of 91.....the recommended minimum. You'll stop for gas twice as often.......and you'll need to remember which grade you pumped last! But it does work.

As discussed by others, low rpm's is really a key component to great gas mileage, around 2000rpm is ideal for economy, and that will give you a reasonable cruise of 60-65mph. I'm really amazed at the great mileage we get: since we bought last November, never had mileage to drop below 20mpg. 2000mile trip to Florida: averaged 25-28mpg.

For acceleration, we ride our motorcycles, or our old Miata!

Horta

93 only for me!!!

Now for my RX it only requires regular unleaded so that all it gets. I think that is 87?

LSPiNoY

iTrader: (1)

i use premium

Lexusfreak

Sunoco Ultra 94 is the best gasoline available in Canada & it's all I use. I used Chevron 93 with Techron when I was on vacation in Florida......(along with a 20oz bottle of Chevron synthetic fuel system cleaner available at popular auto part & department stores) & I once again got 2 tanks full with 500 miles! (800kms).

lorenzo816

There was a story in the paper here recently about octane.

So I help this helps.

When you pump mid-grade in your car. most gas stations only have a Low grade and a High grade, so it blends them together to get a mid-grade octane rating.

matthaven - has a good idea though. Because some of the older LS's need 91 not 93-7.
It is all about compression and combustion.
WIth a higher octane your cylinders could be pre-combusting the gas and not the spark plugs.
A friend told me that if you compressed most anything hard enough it would chemically transform or combust. (think hard science here - lab coats and all)
Lower octane - well, we know what that does.

Years ago, we believed that higher octane meant cleaner fuel. Not TRUE.
It all depends on the refiniery (sp?)
Gas can be orange-juice colored and still pass some state inpsections.

So be ware of what you pump, and change gas stations frequently.

I am going to try the half full method, and go for a 91-2, like Matt said.
I had a V8 before and you do notice a difference. So run high all the time or run both, but NEVER Low Grade in a High-octane engine!!!!.

Oh and change your fuel filter according to the dealer specs!!

Lorenzo
92 LS400 174k

denverdog

my '93 has 190,000 miles. i tried running midgrade gas in it and have had no knocking and no noticeable performance degradation. my understanding is that the higher octane is primarily, if not soley, to stop knocking in a high compression engine. is there any other deleterious effect?
i got the car wwith 88k on it and have always put "mobil 1" in it. i had a one-time puff of blue smoke when the car was started for a minute, then shut off, then started again an hour later. a mechanic told me this indicates a valve sleeve is going, but that it is not worth the cost to repair if that's all there is. he had me switch to 10-30 from 5-30 and that seems to have taken care of the blue smoke incident. other than that the engine is still silky.