Yes I've read that thread. Where I live the ambiant air temp can reach 125+. And we also have no humidity in the summer time here. Maybe 6-10 %.
Compressing air also creates heat. With high intake temps and low octane the fuel with the slightest bit of compression wants to ignite on it's own.
Now cooler climates and higher humidity will play into the picture also. Slowing detonation. That's why some people in cooler climates have no problem with lower octane.

 

^ we are about to get a snow storm today. ( 4 - 10 in ),,, trade you.

 

gotcha

 

Well,,,,NO.

 

Remember IAT is NOT ambient.

 

Higher octane, lower cost.

Mixing 4 parts 87 with 1 part 93 will result with about 90-91 octane.

Most people don't know that.

I put 3 gallons of 93 in and 9 gallons 87 (3:1). Just under a buck a tank more, where filling with 89 would be about $1.85 more. I do the same with my CX7, and burn 2-3 tanks a week of gas between the two.

BTW, if I run 89 in the CX7 it knocks noticably. Mixing it 4:1 doesn't, so its a safe bet mixing it at 4:1 results with higher then 89 octane.

 

^ Check your math. (4(87)+93)/5=88.2 not 90-91 and that assumes linearity. And that would be 4:1 not 3:1.

And (3(93) + 9(87))/12= 88.5

All that work to save .85 a tank?

 

Valpac is on a mission to correct us today. LOL

 

It's not "linear".

It takes about 30 seconds extra per fill. May not seem like much but over a year thats about $170 for an hour's work, and thats after taxes.

 

so how did you arrive at your figures? formula?

 

here in pa if it is cold i'm talkin 50 or less 87 worked fine for me but i parked it now and drive a nice $350 1988 plymouth sundance lol........summertime its only 93 octane for me and nothing else only 20 to 30 cents more per gallon....thats why I work to pay for stuff

 

Given how advanced modern-day ECU's are I really doubt you'll have any problems with running a lower-octane gas. You'll just run the risk of losing a little horsepower I'd imagine.

 

nah, not really. its just there is so much info that is just thrown around carelessly thats all.

 

i've been running 87 the last few weeks. normally i run 93. i've no problems whatsoever. i cant tell a difference in power or sound. or anything.

i run chevron gas exclusively, whether its premium or normal.

 

I used 91 for the 1st year 87 for the last 2 1/2 years. It seems to run the same. I get 22 - 24 mpg on country roads and hit 9k at least 1 time per drive often shift around 7 - 8k while accelerating. Great car

 

I have a 2004 that has run almost exclusively on 87 with the once in a while 91 or Shell V-power. No problems at all and I feel no difference in performance, doubt that the average owner would unless really into racing, etc.

From the 04 Owner's Manual
"Your Mazda will perform best with Premium Unleaded 91 Octane
You may use a regular unleaded fuel with Octane Rating from 87 to 90 but this will slightly reduce performance. Fuel with a rating less than 87 could cause the emission control system to lose effectiveness. It could also cause engine knocking or serious engine damage."

Note that they also say never to add fuel system additives or cleaning agents other than those specified by Mazda (but how many of us are talking about pre-mix, Techron, Seafoam, etc???? Why would we question the use of 87 Octane but consider additives?

Personnally I am using Idemitsu Pre-mix (6 oz when I fill up at the light about 13 gallons) since about 60 K miles after reading the entie thread on Pre-mix I felt that it is a little additional insurance. BTW original engine...76K miles now and never had any engine problems. Did all the recalls and do all of my own oil changes (Castrol dino oil) and plugs.

In areas of extreme heat or FI applications, I can see the higher octane helping. Whatever works for each owner but if you try 87 make your own decision on performance. Many of us are using 87 without any problems.