Octane Recommendations for Highlander

joconnor

Hi Everyone
I have 2006 Highlander AWD 6cyl. I only get 12 mpg. Veh has 4812 miles. I use 93 octane only. Tires are fine. No problems otherwise. Rarely use A/C or defroster. Some street and highway driving. I work midnites so no traffic to sit in. Otherwise no mechanical problems. I have a 2002 Highlander FWD 6cyl 37k and that gets 20 mpg on 93 octane.
Dealer suggests I use the 91 octane (as the manual says) Said that it may actually be too 'rich'. Found that weird but......

Any thoughts... Thank you!

mtairyordge

I never new the HL manual recommends 91 Oct. I have use regular in the 3 I have owned, 2001, 03 and 04. I get 22 MPG every day in the 04 and as many as 27 on the highway in the 04 on regular unleaded. Now I have used the STP Octane boost, especially on the highway trips.

The real culprit is the way the HL is driven, I use the egg between me and the accelerator method. Works evry time. I usually am really gentle for about 50-65 miles then I ease it up to 70 mph and still get 27 average MPGs

nomorebenz

The RON of 91 is the equivalent of 87 at the US pumps.

Higher octane as well as computer controlled ignition timing keeps the gas from igniting at the wrong time in a higher compression ratio engine. Engines with compression ratio's above 10:1 enter into that range.

The Highlander's 3MZ-FE engine has a ratio of 10.8:1. The computer can adjust for the use of 87. If you want "increased" performance, use 91 or higher as the user manual suggest for such.

wwest

"computer controlled ignition timing..." is no longer the primary resource for tuning the engien for differing octane ratings, not since the days of carburation anyway.

EFI, Electronic Fuel Injection, is now the primary "adjusting, adjustable" resource for the computer to use to prevent engine knock.

kenlw

timing is modified using the knock sensors to adjust the timing of the SPARK to accomodate lower octane fuels.

EFI just regulates the AMOUNT (and in some cases the timing of) the FUEL; the Electronic ignition controls the amount and timing of the SPARK, which is how knock/low octane fuel is addressed.

EFI won't address low octane fuel.