ABTOMAT

What octane do you use 87 or 93 ? I was told that if the engine was made to use 87 it would hurt it to use 93 .

JGage

I use 87...
If your auto requires 92/3 then you must use that. But, if your auto is okay with 87, you can use whatever you want.
If you motor is knocking, then you need to bump up the octane.

4RUNR

Since we are on the topic, anyone try higher octanes + advancing ignition?

FUGGRWE

Nothing but 87.

Ben(Miami)

I doesn't hurt, but it's a complete waste of money. No performance gains whatsoever if that's what you're looking for (actually, the higher the octane, the "harder to burn" the gas is). Detergent/additive packages are pretty much standard across the board these days (or so I hear). The only reason to go with a higher octane rating is if you have knock or ping (can happen on older engines with carbon deposits inside the cylinder), if you're blown or boosted (higher cylinder pressures and increased latent heat can lead to detonation), if you're running nitrous (more safety range against detonation?), or if you've got plenty of money to burn every time you fill up. If it's the latter, please let me know--I'll send you my address and you can send some of that cash my way!

Regards,
Ben(Miami)
'02 Limited 4X2

rwmorrisonjr

How about those of us who live in high altitude states (CO, WY, UT, ec.)? We have 85, 87, 91 out here and its always been a questions for me. I personally run 87 and get great mileage but am I wasting my money? Will the 85 harm my engine in any way?

mtnfreak

Always been a puzzle to me too, Jr. Conoco says it's because you don't need the higher octane at lower atmospheric pressure, but 9:1 compression should negate that (my non-scientific opinion). Anyway 85 octane here (30 miles from the refinery) costs the same as 87 octane in Goodland, KS (~250 miles from the refinery). I go with the 85 octane unless I'm headed to the hills with a heavy load. Hardly ever have any knocking/pinging and I save over 10 cents per gallon.

rwmorrisonjr

Thanks for the advice. Have found that I get great mileage with the 87 since i have the deckplate and ISR mods on the engine, but maybe that's due to the summer blend fuel right now. I know that the winter ethanol gas drops my mileage by about 2-3 mpg. I'll try the 85 again and see what happens. At least my wallet will be a little heavier with gas prices the way they are.