Own a 1993 240 SX Coupe, 150K, recommended Octane fuel rating was 93+ (Premium) when new. Thinking of using midgrade gas because of fuel prices, can anyone provide recommendations, pro or con? Thanks.

i always used 87 but i had the ka

Tune it for 94/93 they run rich stock- but if you run a e60 MAF, and a stage colder NGK plug, disconnect the fpr vacuume line and plug it. this will lean it out a bit from the maf to the point it will be better on gas and have more power. What mods if any do you have?

you wont save any money. the car will get better mileage with the recommended octane rating so what you save in that cost per gallon you lose in distance per gallon. use the recommended fuel rating...if you cant afford to do so its time to think about getting a different car maybe.

Thanks. I also am in Canada...that's why I had to ask the question :) Gas price difference here (near the U.S. border) can vary by as much as 30 cents per liter (that's 4.54 liters per Cdn gallon - roughly $1.35 more per Cdn gallon, so on a full tank of 12 gallons it's over $16 difference per fillup). Your suggestion of a 91 octane rating seems like the best bet to me. I don't think I would go down to regular (87 octane rating?), but a good midgrade should hopefully deal with the situation ... .I hadn't really considered the ethanol mixture issue, but it's a very relevant point as well.

If you're using 93 right now, don't switch to a lower grade, your engines probably already fucked from using the wrong gas, the recommended is 89, not 93, you were informed wrong. Using higher octane gas then switching to a lower grade will basically cause your engine to fail. Why anyone is telling you you'll be fine is ridiculous. Unless you're running a completely rebuilt RB, or V series engine, you should've been using 89.

Oh Lord, so much bad information everywhere. This is not a matter of cheap or expensive fuel, unless you know how to play with your car's timing to counteract putting other fuels in your car, RUN THE FUEL IT SAYS TO RUN! There are TWO answers to your question the KA24DE (dual overhead cam) is meant to run on premium (91, 92, 93 octane). The KA24E (single overhead cam) is meant to run on 87. So depending on which one you have, there you go. The compression ratio on the KA24DE is between 9.5:1 and 9.8:1 and its a 2.4L motor, big for a 4cyl, and with decently high compression. Running lower octane will cause the fuel to combust before it should, this will cause backfire (you'll hear it), will shorten the life of the motor and will also give you less power. If you run too high an octane (98, 100+ octane) you will get deposits on your plugs, and O2 sensor, and will destroy your catalytic converter because the fuel will NOT combust when it should and will not burn completely, and you will AGAIN lose power and lessen engine life. Run exactly the fuel it states to run (within a few octanes). Do not run 87 because it is cheaper, you will shorten your motors life and will pay more to repair it in the end.