I'm curious as to which octane most people use. When I picked up my car a few weeks back, the salesdude told me that it had Japanese gasoline in it from its trip over, which I found pretty cool, although it probably wasn't the best stuff out there. Considering it was only 1/4 tank full, I filled it up pretty quickly.

I'm just wondering what I should be using. The first time I filled it up with regular, the second time with the mid-level 79 octane stuff. The sales guy recommended at least the mid-grade, but said it depended on how "hard" you pushed the engine. I'm not sure whether I push it too hard or not, I don't drive that much over the speed limit on the highway .

So what grade should I stick with? I'm interested in finding out what other Protege owners go for.

 

79 octane is really low.
I use 87 in my car.

 

i use 91

 

I've always heard that higher octane doesnt make much of a difference unless its like 110 octane (racing). For our cars, the difference between 87 and 91 is probably not that noticable, and it just depends if you are willing to spend an extra buck or 2 for that feeling. A lot of people have said that you should use what the instruction book says or you are just wasting your money. For my 03 p5 the book recommends 87.

 

use what grade the manf. has posted on your gas cap door, or inside your door jam. Our cars p-5 have been set to run on 87, theres no such thing as 79, your just crazy, your cars computer is set to run at 87, any higher grade will leave nasty valve deposits. Usually whenever you buy a aftermarket computer chip, all it usually does for your car is, it bumps up your timing, and changes the computer to run on a higher grade of gas. Look it up,,,,,

 

Is it that time of month again already?

This has been discussed to death many many times. Do a search. Bonus points for the person who points out why Arghman is wrong.

 

uuuhhhgggg, this again. use the search feature, it works!

to boil it down, use 87 unless your car pings. if it pings then use mid grade.
with 79 octane you must live at a high altitude? you can get away with less octane at a high altitude.

 

Check out Howstuffworks.com and look for the article on how gasoline works. Basically, higher octane fuel is only useful in cars with higher compression ratios. My 02 Miata runs much better with 91 octane fuel, but its has a 10:1 compression ratio. The Protege is basically an economy car with a lower compression ratio, hence higher octane fuel will only inhibit the car's performance becuase high octane fuel doesn't explode as well in "normal" engines.

 

Kill this thread....do a search.

 

lower compression and high compression has some to do with octane rating,,,,,,,Ive owned a 1987 merkur xr4ti turbo 2.3 ,,,,basically its a german made ford with a turbo,,,the engine is the predacessor to the pro -5 ,,,,fords version is called the duratec he i believe,,,,but once again it comes down to ur ecu, and I learned with my merkur,,which had the eec-IV,,,,you had to either get a tuner or chip, or ecu from a mustang svo 1986 to get the car to run better or run right with 91 octane,,,,,in fact the 1986 svo mustang had a switch, to go from 87 or 91 octane,,,the difference being once again,,,,engine timing,,,,mass air volume caliberation etc.....so there u have it,,,

 

Dude, what's up with all the commas??

Anyway, the Protege 5 engine is all Mazda. Ford's current 4 cyl engine is called the Zetec. The Duratec you mention is Ford's line of 6 cyl engines.

Back to the original question:
Using higher grade gasoline is not going to net you any performance gains. Unless the manual states that you should use higher octane gas or you are having problems with pinging, stick to 87.

 

Thats frickin hilarious. I'm going to print that out and give a copy to my boss.