RA-BeastMode

Hello all. I have read about over 20 threads about not using 87 Octane in a FD and you should use 93 if available or 91 at the least. However, I keep seeing the back and forth banter about how some people used 87 for years and was fine but others say they are stupid and blah blah blah...I would use the 93 or 91 if I had it available on base but the base only has 89....Now before I get jumped on about Japan having 104 octane or whatever, keep in mind that this gas is over $6 a gallon in Japan. I haven't seen anyone talk about 89 octane though...I assume it is still as dangerous as 87? And I should just bite the bullet and pay anywhere from $70 - $100 a tank on gas?

Everything in my FD is stock and running on 10 PSI. I see many people in previous octane threads say they run 87 just fine...then I see others flame them. I am just looking for a cost effective way to gas up my FD without blowing the engine. If 89 is crap like 87...then ok I'll just have to fork over the cash to the Japanese stations. But if I can run 89, then please let me know. One key note is that the FD is my base daily driver and I never get over 40mph due to the speed limits....off base I don't even drive it. Thanks in advanced guys/gals.

Evil Aviator

Is the octane rating RON, MON, or PON?

Fuel ratings, RON, MON or PON?

misterstyx69

iTrader: (142)

I'm no gas expert,but my thinking is this:
If the car us running good on the current octane of fuel that the "manufacturer" allows it to be run on,then Why change it?
You say that the car is stock so unless you are going to alter the engine and give it more power than the stock setup I would not worry about the octane level of the fuel that you currently use.
If the Country that made the car uses the same octane of fuel IN the car you have then I think that the question is why worry?

KIRAN-TEK

Japanese fuel rating is in RON

Sgtblue

iTrader: (16)

The FD will run fine on 89 as long as boost is kept low. I say that assuming this is your dd, and you need it to get places. BUT, personally I would be reluctant to go WOT/full boost, especially on a cool day. The thing is, in those threads you read, those that posted up that it can be done didn't likely come back on the forum when their engine detonated to say "hey, I was wrong..sorry".
Off-hand one alternative I can think of for you might be a simple boost-activated water-injection system. Probably do it for ~$350 all in. Less than the cost of two or three tanks of fuel off-base. It will absolutely control knock values...which is the risk with low octane. And being simple means it's pretty reliable...and cheap.
If you search in the Auxillary Injection Section under my username you can find a how-to with links to other helpful threads.

Evil Aviator

Yes, but the question is whether the military base is using RON, MON or PON.

sctRota

iTrader: (2)

I might open a flame war but.. I have been using 87 on my FD and previously on all my other rotaries. It does hold a lower octane value and it certainlly will not be as "powerful" as 91+
Gas isn't cheap here too, and I daily my FD. So 87 hasn't given me issues yet so I see no reason to try it out.
However it is important to note that it is at your own risk and it may work for some and not for others. I have heard stories of people blowing up on 87 only because they choose to run full boost and not adjust the timing to compansate for it. If you run stock 10lb, I see no issue. If you have it tuned for a specific octane, then follow what the tuner says.

RA-BeastMode

Thanks for all of the responses. The base uses MON + RON/2 to get their octane values....correct me if I am wrong, but I think this is the same as the States...And yes I do use it as my DD just around base and pretty much have no where around here to go WOT. I have a wife and 2 kids so if we go off base in Japan, we use a bigger vehicle lol. I am just trying to take it easy on my FD and do some reliability mods until I can get it back to the States and start on performance upgrades. Thanks again.

Evil Aviator

Yes, that is PON, just like in the USA. It would be roughly equivalent to 92-93 RON off-base. I think your engine will be OK just as long as you don't put a heavy load on the engine, such as flooring the gas pedal when accelerating onto a freeway or when driving uphill. However, if your engine is dirty/worn and has hot spots, then you may get some detonation. The risk is your decision.

The octane rating is not necessarily related to the energy content (power) of the fuel. In fact, higher octane often has LESS power than lower octane. It really depends on what kind of fuel blend is used to obtain the higher octane rating. For example, ethanol lowers the energy content, while aromatics raise it.

Yes! As you see, there are different definitions of 'octane rating'. Also, there are many other factors that affect the detonation threshold, such as the health of the engine, tuning of the engine, temperature, pressure (compression ratio, boost, altitude), engine load (acceleration, incline, vehicle weight), humidity, etc.

snivley whiplash

iTrader: (4)

hi all,
lets talk about fuel octane ratings in more depth. the rating systems do vary but all come to the same results, how fast does the fuel burn under compression.
It comes down to one thing, burn rate and flame front heat. In a nut shell the higher the number the SLOWER the burn rate, yes slower. So higher numbers burn slower and produce less heat and a slower flame front producing less power, This results in a better condition to control detonation in higher compression conditions as under boost or high compression engines.
If an engine does not have detonation issues it is better to run a lower octane to produce more power, but there is a fine line here and engine set up in very important here as well as meth or water injection to help control detonation, hope this helps in making fuel choices.

Joe

Evil Aviator

Yes, let's shoot down another urban myth.

The octane rating is ONLY the fuel's resistance to detonation under certain lab conditions (MON, RON, PON, SON, etc.). It is not necessarily related to the burning speed, energy content, clean burning, getting girls to date you, or anything else.

See this link for the difference between octane rating and burning speed:
VP Racing Fuel

PS: Since I have already covered the 'clean burning' myth, if anybody mentions it they get a bop on the head.

snivley whiplash

iTrader: (4)

dam evil beet me up for sharing info.........i will keep things to myself from now on

Evil Aviator

... or, you could add that info to your arsenal of knowledge and share it with others.

RA-BeastMode

Some great feedback here. Thank you again. You probably won't believe this but as soon as I ask about 89 Octane, the base changes all of their pumps to 93 this week.....not kidding at all. They removed the old 89 sticker and slapped 93 MON+RON/2 stickers on everything. Go figure. So I guess I lucked out and only pay $50 a tank on base instead of $90 off base. But thanks again for your input fellas....hopefully this thread will help a few others.

fdbeast

buy some octane booster

Sgtblue

iTrader: (16)

Not needed with 93.
Besides, have you ever really read the labels on those octane boosters? Last I knew they advertise raising octane levels in points. So if you started with 89 and the claim is that it "raises octane up to 5 points", the most you will get is 89.5...probably less. And if you bought enough of that magical "booster" to raise it up to 93, you'd spend way more than you would just buying 93 in the first place.