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Mazda RX-8 Prices Paid and Buying Experience

899 messages,  Last post on May 01, 2007 at 1:09 PM

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What is this discussion about? Mazda RX-8, Coupe

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#156 of 899 premium vs regular by kkollwitz Oct 21, 2003 (9:22 am)
I suggest trying a half-tank of regular. My guess is you will not like the way the engine feels running on anything less than premium, and will find premium's extra cost is worth it every time you pull away from a red light.
#157 of 899 fuel by rorr Oct 21, 2003 (10:59 am)
Unless the engine is tuned to actually gain some benefit from the higher octane fuel, you won't see any additional performance. Also, as far as I know, the typical detergents added to fuel to help clean the injectors are in ALL grades of fuel and not just the premium. You don't need to run premium just to keep the injectors clean.   However, for high performance (typically either high compression or turbo/supercharged) engines, the higher octane fuel is necessary to prevent detonation ('pinging') when the engine is under a load (hard acceleration). Many engines which 'recommend' high octane for the best performance/economy WILL run just fine on a lower octane but the engine management computers will adjust the engine timing (resulting in a loss of power AND economy) when the lower octane fuels are used.   This has been discussed many times over other threads but the jist of it is this: higher octane fuels don't have more 'bang' than lower octane. They simply withstand higher compression without preigniting than lower octane fuels thus are better suited to high compression engines. If you don't have a high compression motor, high octane fuel will do NOTHING for you.
#158 of 899 fuel by qbrozen Oct 21, 2003 (12:07 pm)
to prevent knocking when using lower-grade fuel, the engine management system retards the timing. This, by definition, means the spark will occur at a less-than-optimum time. Less-than-optimum means lower power.   Now, I always took that to also mean lower efficiency, thereby more carbon deposits left behind, which, of course, is the cause of dirtier injectors (regardless of detergents). This may be unfounded, but I think it just makes sense. I could be totally wrong, but have yet to find definitive proof either way.   Regardless of cleanliness, I would like my engine to always run at its optimum settings and not need to generate the spark at a less-appropriate time. And, actually, many modern engines have higher compression ratios than the old 8:1 that 87 octane was designed for. If you do have 8:1 or lower, than you are correct, the higher octane should do nothing for you.
#159 of 899 qbrozen by rorr Oct 21, 2003 (2:31 pm)
Makes perfect sense to me.   I had quite forgotten the dirtiness aspect of retarding the timing when running a lower than 'recommended' octane fuel. When I had read your earlier post regarding your desire to run a higher octane fuel in your Forester in order to not sacrifice a single HP or dirty your injectors, I had assumed you were referring to the detergents in the fuel.   I was not aware that Suburu recommends premium for the Forester.
#160 of 899 No Conspiracy Theorists? by carliker Oct 21, 2003 (2:35 pm)
What are the odds that the high octane fuel is just a deal made up between the fuel and automotive companies? I'm always wondering about such things.
#161 of 899 actually, rorr by qbrozen Oct 21, 2003 (2:37 pm)
subaru doesn't, but partly its just out of habit that i do it for my vehicles now and the other part is that, in that particular vehicle, my wife was running regular, but she started complaining of a smell. She tried premium and the smell went away. I never pursued it any further because if the wife is not complaining, I'm happy.
#162 of 899 Have you leased? by smason1978 Oct 21, 2003 (2:38 pm)
Has anyone leased a Mazda RX8 recently.   I am about to lease one and would like to know what money rates / residuals you got. Did you go with another bank?   Thanks!
#164 of 899 Conspiracy Theory: by eyeswide Oct 21, 2003 (5:19 pm)
As anyone who has ever read one of my postings will attest I am totally paranoid, being thus qualified I will take a stab at   "The Octane Conspiracy!" Now as everyone knows gasoline comes from crude oil. That oil has to be refined to produce the gasoline. The highest octanes are separated and hoarded for the use of multi-national corporations, airline companies, and of course the Military Industrial Complex. The dreggs are left for guys like you and me. To keep you distracted the inner circle makes sure that there are three almost indistinguishable grades made from their slops. The common man is then kept guessing and debating what the additives and octane differences really do, while the rich manipulators laugh their way to the bank!
#165 of 899 qbrozen by rorr Oct 22, 2003 (6:25 am)
I sincerely doubt that the premium in your Forester makes any more power or has any less deposits than regular does. Manufacturers are spending billions these days trying to make their engines as clean as possible. To that end, the designs are optimized for particular grades of fuel (the 'recommended' grade by the manufacturer). You stated yourself that reduced power and increased deposits would occur if the timing was retarded. But if the engine is DESIGNED to run on regular, no such adjustment to the timing would be made, therefor no loss of power or increased deposits.   All that being said, if the wife isn't complaining, I say the extra 0.10/gal is a small price to pay. If only all spousal complaints could be so easily addressed.......8^)

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