deckerson5

my 97 LS400 pings a little when it's cold, but not when it's warmed up. anyone know whats wrong and how to fix this?

RA40

iTrader: (6)

What gas and brand?

Only time mine has pinged was some no-name generic gas from a gas station in Nor Cal along the 5 FWY.

LScowboyLS

make sure you are using 93 octane fuel, low octane fuel such as 87 seems like a money saver at first, but even disregarding the engine damage you may be doing (if your knock sensors should ever fail) the real loss is in your wallet, because of the huge reduction in fuel mileage resulting from the timing retardation that your knock sensors/ECU are inflicting as their penalty to compensate for the low octane gas - it's a bad plan!

87 may be 10% lower in price than 93, but your mileage will be off by a lot more than 10%

Gene01

I have been wondering for some time regarding the recommendation to use 93 octane fuel.
The '05 LS430 Owner's Manual (inside back cover) says "... premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher ...".
I am aware of the different octane ratings for a given fuel due to different testing procedures, but that is not the issue here.
What is the source of the recommendation for 93 (presumably the Pump Octane Number (RON + MON) / 2 ).
I have not seen any gas station in So CA offering higher than 91 PON.
Thanks in advance for any information.

LScowboyLS

91-93 are fine, just use the highest you can find, this will help on "load" situations, such as passing going up a hill etc.

I wasn't trying to push 93 vs. 91, but rather trying to get people to avoid the temptation and trap of using 87-89

Gene01

Thanks. I think the data support that using lower than 91 will not save money (due to the retarded timing driven by the knock sensor system input to the ECU).
However, I am interested in the recommendation of greater than 91 (R+M)/2.
This would imply that knock was occurring (which would not be the case with a higher octane fuel).
My understanding is that any octane rating greater than that required to prevent knocking (other than very occaisional light knock) is essentially wasted.
Appreciate all the input.

deckerson5

thanks for all the input...i only use high octane, but in my area it is 91 octane. could it be something else?