Why the hell do 240SXs need premium fuel?

The 240sx KA has higher compression than the ones used in the trucks and the Altimas. 10 more HP. 9.5:1 is enough compression to require premium.

9.5 is no ?mere? compression ratio. If you run lower octanes than ?premium?, i.e., 93, you might get knocks if your knock sensors are not quite up to par. If you run 91 or 89 octane (medium), you probably won?t hear any knocks, but if you do, consider premium. If you try to run 87 and you still don?t hear knocking, all you might be doing is losing performance. I think I posted a response to a guy with a similar question. My answer was that the most you?ll probably spend over buying ?mouse milk? (87 octane), is about $3.00 more a tankful with a 15 gallon tank. Premium is generally about $.20 more than ?regular?. If you can?t afford that, how did you come to buy a car? I know gas is expensive, but it?s all relative. Do you pay $25.50 for a tank of regular, or $28.50 for premium? Ain?t too much difference there, now is there?

NMan

So at what compression ratio should it be required? The compression ratio on someone elses car? I love how people buy high compression/turbo cars and then want to use the CHEAPEST gas they can find!! Of course, you want good performance AND be able to use cheap gas. You'll use cheap gas, the knock sensor will retard the timing and then you'll bitch because it doesn't make enough power.

And I sure don't see how you figure this engine is a low tech piece of crap either. Maybe the old single cam version, again how many camshafts and valves does it need to not be low tech?

9.5 is no ?mere? compression ratio. If you run lower octanes than ?premium?, i.e., 93, you might get knocks if your knock sensors are not quite up to par. If you run 91 or 89 octane (medium), you probably won?t hear any knocks, but if you do, consider premium. If you try to run 87 and you still don?t hear knocking, all you might be doing is losing performance. I think I posted a response to a guy with a similar question. My answer was that the most you?ll probably spend over buying ?mouse milk? (87 octane), is about $3.00 more a tankful with a 15 gallon tank. Premium is generally about $.20 more than ?regular?. If you can?t afford that, how did you come to buy a car? I know gas is expensive, but it?s all relative. Do you pay $25.50 for a tank of regular, or $28.50 for premium? Ain?t too much difference there, now is there?

NMan

Want to try £44 = US$83 per fill for 55 liters in a RS13. And that's cheap 95 RON stuff, 98 RON is at least 5p/L more so it would be £2.75 or $5/tank difference.

And about 1000 tank fulls to pay for the rebuild minus the loss in fuel milage. Hope you put what you save in the bank for future use....

Well, Nissan has asked for premium ever since 1991, when the 240SX switched over to DOHC and gained a 4th valve in every cylinder. But the compression ratio was still 8.6, which is pretty low by anyone's standard. When the car became the S14 in 1995, compression was bumped to 9.5, which is sort of high, and that points to another question: why did horsepower and torque remain at exactly 155 and 160?

Well, 12,000 miles / 24 MPG x $2 (for 87 octane) = $1,000 a year. If premium costs $2.20 a gallon, that totals $1,100. If $2.25, $1,125. If $2.30, $1,150. An extra $100-$150 a year. Adds up over several years.

I just think that any engine that sounds as ordinary as the KA24DE, and makes such ordinary output (64.9 HP per liter), has no right to ask for premium.

And there are plenty of other cars with 9.X compression ratios that don't ask for premium. It seems that when you cross 10, it's mandatory, but not

9.5, and definitely not 8.6.

The 93 and 98 Altimas both has a 9.2 ratio. Never needed premium.

By the way, does anyone have an old Road & Track or Motor Trend and knows the 240SX's steering ratio? I think I remember 17.5.