Regular or Premium fuel in a P5?

M

MexicanDragon

Member
:
2003.5 Mazda Protege5
Hey guys... I searched and didn't find anything for us... so i'll start this.

Just got my MP5... 63k miles... I've only put premium in it in my 1.5 tanks so far (habit coming from a caddy). What do you use, does the 93 i have here work better, same, hurt things?

Keeping it short, on my cell, let me know, thanks guys...

**BRENT**
 
MP5's ECU's are tuned for lower grade fuel. It will run fine with the lower grade fuels. Save some money and put the lower test stuff in it.
 
Doesn't hurt/help anything. But if you plan to continue using it, might as well buy an MP3 ECU and get a couple extra HP at the same time.
 
If you use premium, won't you have less complete combustion and end up with a buildup of crap?
 
I run regular unleaded and dump some fuel injector in there every other tank and once a month I'll fill her up with the good stuff.
 
The P5 is designed to be run on 87 octane, so don't waste your money on premium unless you have the MP3 ECU or a turbo :)
 
The octain rating of fuel does not indicate the quality or temperature of the combustion process, but the speed at which it combusts. The higher the octain number, the slower the ignition.

Without going into the details of "why", using a higher octain fuel in a vehicle tuned for 87 will result in a full burn later in the engine cycle potentially resulting in a minute loss of power and/or an incomplete burn (resulting in decreased catalytic converter life).
 
Last edited:
kcbhiw said:
The octain rating of fuel does not indicate the quality or temperature of the combustion process, but the speed at which it combusts. The higher the octain number, the slower the ignition.

Without going into the details of "why", using a higher octain fuel in a vehicle tuned for 87 will result in a full burn later in the engine cycle potentially resulting in a minute loss of power and/or an incomplete burn (resulting in decreased catalytic converter life).
Click to expand...

wow 87 in illionis is considered mid-grade. 83 out of here is considered normal.









hmmmm... no wonder im getting bad gas milage!
 
What about reformulated gas? I use Shell 93 octane as the 87 cuts 40 miles off of a tank. I live in the country and the gas is not reformulated. I work in "the big city" and their gas is crap as it is the winter blend reformulated. I only got 300 miles to a tank whereas I normally get 415+- when I get the 93 octane by my house.

You can argue the 93, 87 debate but I have seen an improvement in both mileage and performance with using the 93.

Seems that the debtae should be 78 vs. 93 and reformulated 87 vs. noreformulated 93. Not all of the counties here are on the bandwagon for reformulated gas. The carbon buildup from the reformulated gas is horrible. My camry requires 93 and when we live in an area with reformulated gas I had to seafoam the pcv system at every oil change.
 
winter mix gas ftl. my gas mileage is terrible, a compounded effect of winter blend gas and the little shiny snail under the hood :p
 
well I will be switching to 93 octane in about 2 weeks 1 full tank of gas gets me 230 miles (yes everything is fine with my engine) which lasts me 2 weeks my job I 2 miles from my house I think my gas milage is so crappy because its a combination of starting my car sooo much and using crap gas. iit takes a lot of gas to start a car and I start it at least 6-8 times per day and drive in stop and go traffic and I always romp on the engine.

93 Octane Here I Come!! Woot turbo!
 
when i got my mp5, i first started using 93 octane. i wanted to try 87 to see the difference, and according to my g meter in my car, the car was actually faster with the regualar gas.

now i have an mp3 ecu and i only put 93 in it, and the g meter goes higher(rockon)
 
jamesk said:
when i got my mp5, i first started using 93 octane. i wanted to try 87 to see the difference, and according to my g meter in my car, the car was actually faster with the regualar gas.

now i have an mp3 ecu and i only put 93 in it, and the g meter goes higher(rockon)
Click to expand...


G meter?
 
Matthew1785 said:
G meter?
Click to expand...

gtech1.jpg


?

once it gets warm out and I can put my sticky tires back on I need to test my car to at least see that the estimated whp (with air resistance factored in) is more than it was before (120whp).
 
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