What Octane?

[VX KAT]

I was curious about this so I actually experimented with regular vs. premium. I ran spreadsheets (I know, pretty geeky) to calculate my gas mileage based on what octane I was using and where I was buying it, in case that had an impact. Based on almost two years of testing, I'm getting 2-3 MPG higher when I use the 87 octane fuel as opposed to the 91 (or 93 in a couple of cases). I don't notice any appreciable difference in the sound of the engine or the amount of power I'm receiving, but since that's all subjective and the only thing I am actually measuring with any sort of rigour is mileage, I can't say for certain.

I do know that I am running a completely stock engine.

Great data! Any winter blend vs. summer blend data or impressions, or did you do just an overall annual average? Probably hard to determine exactly when the blend changes anyway (although seems like I've seen stickers on the pump when it's the winter mix??)

[circmand]

Great data! Any winter blend vs. summer blend data or impressions, or did you do just an overall annual average? Probably hard to determine exactly when the blend changes anyway (although seems like I've seen stickers on the pump when it's the winter mix??)

Its not like the stations use different tanks or change over at the same time. Basically the refineries change over thn the tankers pick up the new fuel and just fill up the tanks with the old fuel and it mixes

[Luna X]

with prices the way they are..... good 'ol 87 sounds just right to me...

[BeeVenom]

I'm only run 93 octane, but that's cuz of my Super Charger being there. I'm averaging about 19 (+)(-) at fillups. Thought a couple years ago that I was surpassing 21+ highway but my calculator must have been haywire back then! Mileage is pretty consistent and speed does make a difference (ie: 55 vs 60 vs 65 vs 70). Run BP premium all the time and get their 5% rebate which helps make it feel a little better. Not much, but a little better!

[H3_VX]

Just to poke my nose into this thread, is it true if you use synthetic oil and then switch back to regular it could damage the motor?

[89Vette]

Just to poke my nose into this thread, is it true if you use synthetic oil and then switch back to regular it could damage the motor?

Only on Sundays when the white Rhino charges his Visa card.

[evillecutter]

93 (or 92 at some stations) octane - 300 miles to a tank - ive never driven to where the gas light has come on but ive noticed that when my gas gauge reads half a tank i can only put about 9 gallons in it until it is completely full -so im thinking if i have a 22 gallon tank when im on empty i could actually still have a few gallons left in there - and with the difference between an entire tank of 89 vs 93 being less than $5.00 id rather just run the cleaner stuff just to be safe

--funny (sad) how in 04 people in this thread were complaining about $1.84 a gallon

[VX KAT]

93 (or 92 at some stations) octane - 300 miles to a tank - ive never driven to where the gas light has come on but ive noticed that when my gas gauge reads half a tank i can only put about 9 gallons in it until it is completely full -so im thinking if i have a 22 gallon tank when im on empty i could actually still have a few gallons left in there - and with the difference between an entire tank of 89 vs 93 being less than $5.00 id rather just run the cleaner stuff just to be safe

--funny (sad) how in 04 people in this thread were complaining about $1.84 a gallon

My tank runs that way also....apparently more gallons fit in the first half of the tank ()....
oh, and it's capacity is 22.5 gallons....cuz ya know that extra half gallon can getcha a few more miles


I've gone as low as the needle can go, (but no light) and total fill was only 18.80 gallons. and 297 total miles.....
I've never hit a 300+ miles tank yet....cuz I think it's really close to empty and don't want to run out....but it appears I've got about 50+ miles left (3.7 gallons @ 15 MPG).

But living out in the boonies, and often driving off road in the boonies...that hidden 3 gallons is a great safety cushion.


OCTANE- several past discussions about Octane vs. MPG.
Some say higher octane gets higher MPG.
Someone ran a real detailed experiment on this. Can't recall who...(maybe HiredGoon??)
Think they found higher Octane (Premium) DID increase MPG a bit.

I tried it...3-4 months Premium vs. many months regular....not much difference in MPG that I could see.

[evillecutter]

i didnt get all the way empty but i get almost exactly 75 miles per quarter tank -i just changed the fuel filter too maybe that could help mpg? thought it couldn't hurt because the old one looked like it hadnt been changed in a long, long time - and ive never really heard anything about higher octane gas getting better milage, but i have shortly researched how they make the different grades and unless we are being lied to (wouldn't doubt it) the higher octane is supposed to leave less gunk in your engine i.e. burn cleaner because it has less impurities in it - but either way i didnt buy it to save on gas - its worth it

[VX KAT]

but either way i didnt buy it to save on gas - its worth it

Ain't that da truth!! Fun is more enjoyable than MPG to me...

[89Vette]

OCTANE- several past discussions about Octane vs. MPG. Some say higher octane gets higher MPG.

Even within this thread, you'll find others who said the opposite...that lower octane produces best power by not inhibiting the "burn". Unless someone has run scans and sees evidence of timing retard, I gotta think 87 is best -- like the owner's manual states.

They wouldn't have coded timing tables for 93 octane and said use 87. Every few months you see how people are wasting their money buying "high-test" thinking it's better for their car. If it doesn't require it, it's not better.

btw...my guage hangs on full until 40-50miles, then it drops like a rock to 1/4 tank. So, it takes 50m to get down to full...and 25 miles to drop the next 1/4 tank. Pretty nice calibration their Isuzu techs!

Yeah...I finally broke my personal best and hit 16.5mpg last week. I finally got a few miles/day on the hwy. But, it's not the best cause it's during the to/from rush hour.

[RickOKC]

I always use 87 octane and my mileage is all over the place. I was really worried after one road trip when the VX was about 4 MPG lower than usual. The next day I took a shorter highway trip and it was suddenly 2 MPG higher than average. On the way back it was 2 MPG lower than average. Now I keep an eye on wind speed and direction - apparently it makes quite a bit of difference!

[ALC1717]

You Guys that claim you get over 300 Miles per Tank is hard to believe unless that is strictly Highway Driving ONLY ! There is NO Way the VX gets 300 Miles per 22 Gallon Tank driving Locally and if you guys claim it does with all due respect you are all " Full of Crap " ! My VX runs fine with Regular Gas and Oil, that is what ISUZU recommends.

[evillecutter]

You Guys that claim you get over 300 Miles per Tank is hard to believe unless that is strictly Highway Driving ONLY ! There is NO Way the VX gets 300 Miles per 22 Gallon Tank driving Locally and if you guys claim it does with all due respect you are all " Full of Crap " ! My VX runs fine with Regular Gas and Oil, that is what ISUZU recommends.

i was one who claimed that... i and spoke too soon (sorry didnt mean to lie) - i did go from full to 3/4 tank getting 70 miles a few times but that does not happen very often and def doesnt happen on any other part of the fuel guage - i would say 240 is much more accurate for me and i have done everything i can think of to improve the fuel efficiency (i also have no suspension mods and ride stock sized high performance street tires)

[circmand]

Very slow on 1st quarter of tank then you can see the needle moving. Mixed terrain but all pavement and depending on the lights you can get better MPG. I once got almost a 100 miles on the 1st quarter tank but finished at 280 for the tank. The light had just come on so i say 300 is just possible if you are mostly flat or downhill