SEAN_at_TLT

I run premium in my truck because I have the TRD SC but my fathers truck is a 2002 NA. He has been running premium to be on the safe side since the owners manual is somewhat ambiguous.

Apparently there are three ways octane is measured in the US:

1) Motor Octane Number (MON)
2) Research Octane Number (RON)

And the average of the two (which is what is posted on the pumps)

3) R+M/2 method

I know the 87 Octane Rating in the owner’s manual doesn’t refer to the RON, since they give a separate RON rating. However, I don’t know whether it refers to the MON or to the R+M/2 method. If it refers to the MON, then he should be using gas with a minimum R+M/2 octane rating of 89 ((87 + 91) / 2), which is the middle grade at most stations. However, if the 87 refers to the R+M/2 method, then he can use regular gas, which has a R+M/2 octane rating of 87.

Any octane experts out there, or just people who run 87 in their newer (2000+) 4Runners have any input? I know I ran 87 sometimes prior to installing the SC w/o ill affects but I am not sure if Toyota made some revisions to the 3.4L after '99 that require higher octane gas. I'm sure he's fine running 87 but I'd like to see what others have experienced first just to be sure. Also does running lower octane decrease fuel-economy, vise versa or is it negligible. With the cost of gas going nowhere but up I thought this topic might be interesting to many others.

4-RUNNIN' FREAK

A guy I work with has an '00 Pathfinder 3.5 and it says flat out to use premium.
"93 or higher octane" it states in the owners manual.

They are along the same lines of truck as a 4Runner, no?

bamachem

run 87 in the 3.4L unless you have the TRD SC.

the higher the octane, the lower the gas mileage, but the less chance of detonation.

SEAN_at_TLT

Freak, not quite what I'm lookin' for here, but thanks anyway...

Andy, That's getting better, thanks! So the late-model 3.4L's won't detinate under normal circumstances with 87 octane and they WILL also get better mileage? If that's right, about how much better should the mileage be? I'd imagine not very much.

(P.S. the truck looks good again all fixed!)

bamachem

yea, run 87 in the 3.4L engine

it will get about the same, although technically, a higher octane gas "on paper" will decrease the mileage...

lee

ive been running 87 through my 3.4 in my 2001 for the last 6 to 7 months and get better mpgs, same performance... absolutely no ill effects.

so yea, 87 is just fine.

i used to run 89 when i first got her, because i loved my new baby and wanted to give her a step up... then i realized that was really really stupid and a huge waste of money that could go toward my upcoming lift!

bamachem

yeah, i can't WAIT to get my 4.56's in and get this SC OFF so I can go back to 87!

FattyCBR

The US only measures the octane as an average of the RON and MON, not individually. The MON and RON describe the octane rating under different load conditions, hence the different numbers for the same gasoline. Other countries use the one with the higher reading, which is why you see people saying they get 98 octane at the pump, when in actuality it's the same as our 93 octane.

So to answer your question use 87 for NA engines and 91/93 for boosted applications. The less octane you can use the better, because the lower the octane the more energy it contains for a given volume.

DOT3

Bottom line is if your engine pings excessively (like the 22r does on 87 oct), your efficiency is worse. Short periods of pinging are normal and indicate that your compression ratio is maximized for the grade of gas your using (a good thing). My 22r compression ratio is so maxed out on 87 oct that I can tell when the barometric pressure is high by the amount of pinging I hear.

My reference books indicate that all grades of gas have the very nearly the same heating value, so your gas mileage should not vary with the grade.