Which one is required for the Navigators. For year 1999-2002

Thanks

 

Your owner's manual tells you. A sticker on the gasoline cap door tells you. Please don't tell me you own a vehicle with NO owner's manual. You should make that a condition of sale when you buy; you'd be surprised how quickly the dealer/owner comes up with one when you say that. Back to your issue, I understand they require premium fuel (90-93 octance). One guy in a recent post said his Nav knocked with anything less than 91 RON. Your success with a particular blend/grade is dependent upon your area's latitude, altitude and season.

 

And cleanliness of the engine's EGR ports.

 

Run at least 91, I run 93 (I have a chip). Our big V8's like the more combustible stuff.

 

High octane gas is actually less combustible - it prevents higher compression motors from knocking by slowing the combustion rate and preventing pre-detonation. Running high octane gas in a motor that doesn't need it can actually be detrimental - you end up sending some unburned gas out the exhaust resulting in a hotter catalytic converter and lower MPGs, and you get no increase in power. In addition, regular and premium gas have the same detergent additives (it's mandated by uncle sam) so there is no advantage there either. So if your owner's manual states 87 octance (like my 98' 4.6L) then that's the best choice - there is no advantage using premium. If your owner's manual says to use 91, you will see loss of power using 87, but you most likely won't have knocking or cause damage, since knock sensors in the motor will change the timing or some other ignition parameter to prevent knocking.

 

Technically, you are right, there are a number of studies/web sites that show it. Just read the first part of my post a little more closely. I have a CHIP! The Superchips Flash Module that I have installed on the CPU of my vehicle requires at least 91 octane, but recommends 93 octane. The results being increases in horsepower and torque with the recommended use of 91-93 octane fuel. If you haven't chipped/programmed your vehicle, the higher octane fuel is not recommended.

Geez, there's always one on every board...........

 

but, I have to run 89 octane in my stock 5.4 or it pings likes crazy. I have tried everything else to fix the ping problem and the only thing that does it is running 89 or higher.