What grade should I be using on this 1985 2Dr Hatchback, Carb 1600 Ea81? I am getting 28MPG now using regular unleaded. Would I get better than that, and would it increase performance if I used Premium gas? The book says 91 octane and I have been using 85. When I bought it the guy told me he used regular unleaded so I didn't change. So what are you getting for MPG and what grade of gas?

I have been told also that higher grades in high altitudes is bad for the motors.

i wonder why the owners manual says that for your engine. with the price of gas id stick with regualr. that mileage sounds low to me, i got 36 mpg on a good day out of my wagon.

your economy will go down if you go to a higher test, stick with the min if you can avoid detonation, when you drop down to the lower elevations you may need to go to midgrade, but probably not.

i wonder why the owners manual says that for your engine. with the price of gas id stick with regualr. that mileage sounds low to me, i got 36 mpg on a good day out of my wagon.

 

The manual may not be a US one. Octane can be measured in two ways, Both japan and New Zealand measure it differently to the US. ie our regular is 91, premium is 96.

the 1985 buyer's guide spec's 90 or higher (us method) - I run midtest (89) and get better performance/mileage than regular (87) by a 2-3 mpg difference - has always been that way since new - runs like a dog with regular - however I don't mess with premium - wayyy too expensive

Thanks for all the input. I used to own a 1990 Chevy S-10 that ran like caca with regular in it, but ran great with the mid grade. I might try that with this machine, but I am worried that after running regular in it all it's life and then changing will hurt it. I was told that high altitudes and higher grade gas can harm engine components.

High altitutes plus high grade might make it seem sluggish, as the air is less dense and the fuel burns slower. Essentially, you'd be running rich. I don't think that would hurt anything (converter temps might be higher).