87 vs 89 octane in stock 3.4 5vzfe

Mine has always gotten worse mpg with higher octane. I always run 87 now.

 

Usually with higher octane, my truck will run just the same as 87. Maybe 10-20 miles more in a tank and run a little smoother, but that's about all I notice.

Side note, I was towing a trailer one day and decided to try 91 octane and one of those little bottle of octane booster. Filled up the tank and went back on the freeway. Emptied the whole tank in about 75 miles. That was the worst experience I had with higher octane.

 

Ihad said early that I had some mods that let the truck breath a bit better, possibly attributing to the Freeway mpgs I see. (25mpg+)

 

I never see that kind of mileage with my stock motor running 87, 89 or anything else.

 

Not sure man. Most I've ever gotten is 28mpg

 

Most I got was 28 too. That was in an automatic '98. Most I've gotten in my manual '01 is 26. Maybe overdrive on the auto has better gearing. Possibly the diffs had higher gearing. Not sure. Best mileage hands down is in the California/Nevada/Arizona desert. Dry and warm air.

 

I'm also running larger tires, run with a full toolbox in the bed and usually travel at 65-70mph on the interstate so I'm not surprised my mpg isn't great. When I would bump up to higher octane when 87 wasn't available I'd get lower mpgs also.

87 works just fine for me.

 

85 Oct is everywhere around here, probably due to the higher elevations in in the mtns not requiring as high of octane.

 

Same here in Texas with 100 plus degree heat. I have 4.10 gears and 31inch stock tires. I believe the auto OD is .82

 

The only purpose for higher octanes is to resist knocking on higher compression ratio engines. IE, engines with turbos/superchargers/highly compact combustion chambers. if your truck actually benefits from higher octane fuel, there is something very wrong with your engine.

 

Resistance to knock allows the ignition timing to be advanced making more power and/or the need for less fuel. Only some modern cars have the ability to take advantage of this or others with the help of a aftermarket tuner.


This is my understanding anyways

 

In higher elevation, like Ut, our common gas grades that are seen on the pumps are 85, 87, 91.

I run 87 in my cars.

 

thats correct to a certain extent. "Resistance to knock allows the ignition timing to be advanced making more power and/or the need for less fuel" doesn't apply to our engines that are running optimally. an optimally running engine (with less than 9.5ish compression ratio) cant differentiate between octanes because the spark is GOING to ignite the fuel at the same exact time no matter what available octane you have in there.



and this part "Only some modern cars have the ability to take advantage of this or others with the help of a aftermarket tuner." only applies to vehicles that have such a high compression ratio (starting at above that 9.5ish) that lower octane fuels will be noticeable by the computer through the knock sensors.

the only time our trucks are affected by octane ratings are if we have add-ons or issues in our engines that cause knocking. usually superchargers/turbos/intake leaks, whatever isn't stock design.

 

You do know that our trucks have 9.6:1 comp right? not that it changes toooooo much

 

I know i was just pointing that out. The 91oct tune for these trucks only net about 5hp. That is what uni chip told me when i emailed about their tuner a while back. Definitely not worth $700 and having to use premium fuel

 

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FWIW ... I just switched to 89 today. Had some rattle noises (like floating valve noises) in engine, when it gets hot & humid and under at load (before downshifting) at times.

Going to see if the noise is still there in a couple of weeks.

PS ... I know Toyota says it's supposed to run on 87 octane.
.

 

The lowest Octane you can run without preignition(detonation) is what you want.