Caniac14

Hey everyone. So my wife, and her parents, and everyone else she has "talked" to about it, say there wouldn't be an issue running 87 in my 1996 LS400 instead of 93(I religiously run V-Power)
She says, imagine how much money we could save if you used regular instead of premium.

I tell her, I trust what the people that make the car say, and they say premium unleaded only. The only thing I know "scientific" about the subject is that different grades combust slightly different but I don't know exactly how, and how to explain it to her properly?

I am more than certain I am right, so can someone give me a definite yes to the subject, possibly with some science/facts/data backing it up.

And if I am wrong, please educate me.

I need the answer to be definitive as possible so she can finally stop nagging me about the issue.

I love my LS, and I only put the best in her, so I wouldn't dream of putting anything other than V-power in her unless it was absolutely 100% ok to do otherwise.

lexmoose

My biggest issue is ethanol, that **** is killing our engine

Luckily in your state you seem to have lots of ethanol-free gas
http://pure-gas.org/index.jsp?stateprov=NC

Try ethanol-free 87 and see if the engine start knocking, if it does try 89 or switch to 91. Don't go higher than 91.

I was running 94 up till 3 weeks ago when the cold mornings started. A few mornings the car had a hard time to rev up, it would shake and stay in the 100-200 rpm for a few seconds and then come back to normal. One day after filling up with 94, I went inside the garage and explain my problem and tell the guy that i'm using 94 to make sure the engine have the best... He explained to me what the octane rating was and how it was affecting the engine, so he's telling me that it probably need a good tuneup (air intake, electrical) and the harder to ignite 94 accentuate the problem. 3 last fill up i used 91 and it started like a champ since then with even colder temperature. I'm a believer

Now I just found out that Petro-Canada now have up to 10% ethanol in all their grade... Time to switch to Shell 91

lexmoose

Maybe what that mechanic told me wasn't true. But what he told me is that the higher the octane the higher the gas will be hard to ignite. Higher octave is used in higher compression engine to prevent knocking (premature ingnition).

RA40

iTrader: (6)

Beaten to death but use what you feel appropriate

https://www.clublexus.com/forums/ls4...er-thread.html

https://www.clublexus.com/forums/ls4...er-thread.html

This discussion on a Porsche forum about ethanol:
http://www.pistonheads.com/gassing/t...+scoring+found..

This article:
http://articles.latimes.com/2012/mar...grade-20120329

Bottom line is the engineers have made allowances for budget owners who feel they will be saving $. In the long run only your wallet and any repair bills will determine the outcome.

(I wonder what fuel is being used in the LS400's with fouled O2 sensors and suspected cat issues?)

dicer

Electronic engine controls compensate for octane variances. lchouinard the mechanic told you correctly.
The best way to lower costs and kinda be safe at the same time is to mix lower and higher octane or mid grade.

johnnyg66

I have only used 91 here but recently they now sell 87 with no ethanol for same price as 91 with ethanol. I might try that and see how it works. Now I do not drive mine daily so a tank full will last me 2 plus weeks unless i go out of town.

Legender

How much $money$ are we really talking about here?
When I did the math with my dad it came out to about 40 cents extra per gallon, here in Texas.
Averaging 15 gallons a fill up. that's $6 a tank. At two tanks a month that is less than $150 a year in savings.
To me... not worth it.
To you... maybe so.
You don't have to imagine how much money you could save.. .you could just do the math and determine if it's worth it for you.
As for me, I like to use it and care for it in the way it was designed. So yes, I buy the premium gas.

MrAM

The owners manual states to use 91 or higher and that 91 should only be a temporary measure. To use any lower could cause pre-ignition issues and permanently damage your car.

http://drivers.lexus.com/t3Portal/do.../sect0/040.pdf

mappo

That manual is worded poorly and causes confusion. It sounds like it's saying to use at least 91, but 91 can be used temporarily if you can't find 91. What it's trying to say, and what the 2000 manual says more clearly, is that you should use 91 but can use 87 temporarily. The confusion is because of the difference between Octane Rating numbers and Research Octane Numbers

The 2000 manual says:
Select premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher for optimum engine performance. However, if such premium type cannot be obtained, you may temporarily use unleaded gasoline with an Octane Rating as low as 87 (Research Octane Number 91).

http://drivers.lexus.com/t3Portal/do.../00lsom/62.pdf (page 5)

TMAdash1

iTrader: (1)

When I bought mine I found old records of when the previous owner started using 87 octane but I've been using 93 since I've bought it.

Pretty sure PO had it like that for years, car still runs great with no issues. Like they've said before the ECU will compensate. Your car won't blow up put whatever gas you want in it.

MrAM

In all fairness, that's a 2000 model. There could be many engine differences between 96 and 2000.

This is incorrect. Higher octane fuel reduces pre-ignition. Pre-ignition/knocking can cause stuff like this: https://www.google.co.uk/search?q=kn...ih=750&dpr=0.9

MikeFoxx

iTrader: (8)

Goes cheap on gas but throws money away at the bar...

I still don't know why people have a hard time just using 91. It's not a Ford tempo. With gas prices dropping even 91 is currently cheaper than the lowest grade a couple years ago. I ran 91 in my 1992 sc400 and 96 impala SS both gas guzzlers... it's peanuts at the pump.

mappo

I haven't seen 91 in a long time. The only choices at the stations around me are 87, 89, and 93.

MikeFoxx

iTrader: (8)

^^^^ likewise... haven't seen 93 here in NorCal only 87 89 91 and jet fuel ^_^

TMAdash1

iTrader: (1)

Well I've been running 93 for the past year and a half, hopefully that fixed the hole in my piston